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Point source exposure of cattle to Neospora caninum consistent with periods of common housing and feeding and related to the introduction of a dog
Abstract
Eight dairy herds with evidence of post-natal transmission of Neospora caninum were used to test the hypothesis of a point source exposure by a retrospective analysis of the housing and feeding of infected age-groups. The first N. caninum-associated abortion or birth of N. caninum-seropositive offspring from the post-natally infected age-group was considered as the first indication of the infection. In seven of the eight dairy herds, a point source exposure to N. caninum of the infected age-groups was found during a limited period of common housing and feeding. In all herds studied, the analysis indicated that the cattle had been infected shortly before the first abortions occurred. In all, except one herd, the post-natal infection was more directly related to housing than to feeding. Therefore, it appeared that the feed was contaminated in the feeding alley. In one herd, the total mixed ration was found to be the probable path of infection. In all farms studied, a new dog (young, adult dog or litter) had been introduced within a period of 1.5 years prior to the first indication of N. caninum infection in the cattle. As there was evidence in all herds of vertical transmission of neosporosis for years, it is hypothesized that the newly introduced dog was infected with N. caninum by materials from already infected cattle and subsequently transmitted the infection to other cattle by shedding of oocysts.
... Abortion storms can occur either in herds with recently infected cows (horizontal transmission) (Thilsted and Dubey, 1989;Waldner et al., 1999) or in herds with moderate or high seroprevalence due to previous N. caninum infection (Thornton et al., 1991;McAllister et al., 1996a;Moen et al., 1998;Wouda et al., 1999a;Dijkstra et al., 2002a). Point-source epidemics often producing abortion storms are caused by sufficient exposure of a large number of susceptible animals to a causative agent during a brief period, usually through ingestion of oocyst-contaminated feed or water (Yaeger et al., 1994; Chapter 1: General introduction Thurmond et al., 1997;Moen et al., 1998;McAllister et al., 2000;Dijkstra et al., 2001a;Schares et al., 2002;Dijkstra et al., 2002b;Crawshaw and Brocklehurst, 2003;Bartels et al., 2007a;Basso et al., 2010). ...
... The presence and number of N. caninum-positive domestic and feral dogs on a farm (Paré et al., 1998;Bartels et al., 1999;Mainar-Jaime et al., 1999;Wouda et al., 1999b;Romero et al., 2002;Dijkstra et al., 2002a;Dijkstra et al., 2002b;Schares et al., 2004;Rinaldi et al., 2005;Corbellini et al., 2006b;Nasir et al., 2010;Imre et al., 2012;Ghalmi et al., 2012;Asmare et al., 2013), or the presence of wild canids in the area where farms are located (Boulton et al., 1995;Barling et al., 2000;Stoessel et Chapter 1: General introduction al., 2003;Gondim et al., 2004d;Hobson et al., 2005;Frössling et al., 2008;Asmare et al., 2013), have been associated with an increased risk of Neospora seropositivity and abortion. Oocyst-contaminated pastures, fodder and drinking water are regarded as potential sources for postnatal infection and similarly, farmers of herds with evidence of postnatal infection were more likely to have observed dogs feeding on bovine placenta, uterine discharge, and colostrum or milk than farmers of control herds (McAllister et al., 2000;Dijkstra et al., 2002a;Dubey et al., 2007). ...
... For example, measures to prevent dogs from feeding on infected placentas or foetuses have been associated with lower seroprevalences (Schares et al., 2004;Corbellini et al., 2006b;Ghalmi et al., 2011). Use of supplemental feeding may increase the risk of horizontal transmission through faecal contamination of feed and water sources by a definitive host in regions with an abundance of wild canids (Ould-Amrouche et al., 1999;Barling et al., 2000;Sanderson et al., 2000;Barling et al., 2001;Dijkstra et al., 2002b;Frössling et al., 2005;Klevar et al., 2010). ...
Despite Neospora caninum being recognised as a major cause of bovine abortion, its pathogenesis is only partially understood. Evidence of immune mediated placental pathology has been reported as being responsible for compromising pregnancy probably due to an exacerbated Th1 immune response at the maternal-foetal interface. Different clinical outcomes are known to follow experimental infections at different stages of gestation, with foetal death being the most common finding during early gestation infections, and the birth of live congenitally infected calves following infection in mid or late gestation. The aim of the current study was to characterise the placental cellular immune responses and cytokine expression following experimental Neospora infection during pregnancy. Placentomes were collected from cattle experimentally inoculated with the tachyzoites of the Nc-1 strain during early, mid and late gestation.
Inflammation in early gestation was generally moderate to severe. Differently in mid gestation, inflammation was mild to moderate and minimal to mild in late gestation. Generally cellular infiltrates were mainly characterised by the presence of CD3+, CD4+ and γδ T-cells; whereas CD8+ and NK cells were less numerous. Macrophages were detected in larger numbers during later time-points after infection. A moderate to severe infiltration of IL-12, IFN-γ and TNF-α expressing cells was observed in the placentas collected in early gestation. This infiltration was more pronounced in the samples of placentome collected from dams carrying a dead foetus or in those that had aborted, compared with mothers carrying live foetuses at the time of sampling. The distribution of the cellular subsets observed in the three studies was similar. However, cellular infiltrates were more severe following infection during the first trimester in comparison to the second and third trimester. Similarly, the infiltration of Th1 cytokine expressing-cells was more severe in early gestation compared with the milder and more minimal infiltrations observed following N. caninum infection in mid and late gestation, respectively. These results may explain the milder clinical outcome observed when animals are infected in later stages of pregnancy.
... caninum [122,123,149]. dans les allées, les mangeoires et sur les stocks d'ensilages ou de foins entretien le parasitisme dans l'exploitation [115,117]. La quantité d'ookystes excrétés varie en fonction de la souche infectante, de la quantité de parasites ingérée, du statut immunitaire du chien [392] et du degré de fraicheurs des tissus bovins infectés consommés [187]. Cependant, certains chiens infectés n'excrètent pas d'ookystes [118,392]. ...
... Dans la plupart des études épidémiologiques portant sur la n é o s p o rose bovine, la présence et le nombre de chiens (hôtes définitifs de N. caninum) de ferme [8,37,87,117,289,341,389,448] ont été des facteurs de risque d'infection des bovins. Par analogie avec T. gondii, l'introduction d'un nouvel hôte définitif est d'une importance cruciale pour le cycle du parasite [98]. ...
... En eff e t , la séropositivé dans les élevages a été associée à la conduite du troupeau. Ainsi, les animaux en divagation libre en enclos, partageant les mêmes mangeoires ont toujours été plus infectés [117]. Par ailleurs, la séroprévalence a été plus élevé dans des élevages où les chiens ont consommé des avortons et/ou des placentas comparés aux fermes dans lesquelles, la destruction de ces produits est systématique [115]. ...
La présente revue bibliographique fait le point sur l'épidémiologie de la néosporose, une protozoose causée par Neospora caninum. Décrite pour la première fois en Norvège en 1984 chez des chiens atteints d'encéphalopathie et de myosite, N. caninum a une structure et un cycle évolutif proches de Toxoplasma gondii. La néosporose est une pathologie bovine, le chien et certains canidés sont des hôtes définitifs de N. caninum. Elle se manifeste cliniquement par des avortements chez la vache et des maladies nerveuses néonatales chez de nombreux mammifères domestiques et sauvages. L'épidémiologie de la maladie est encore mal connue. Cependant, N. caninum semble pre n d re une place importante dans l'étiologie des avortements d'origines inconnues chez les bovins dans la plupart des pays où il a été re c h e rché. Par ailleurs, la néosporose constituerait un problème en santé publique. (RASPA, 6 (2) : 75-98). Abstract Etiology, pathogenesis and life cycle of neosporosis We reviewed the epidemiology of neosporosis, a protozoosis caused by Neospora caninum. Described for the first time in 1984 in Norway from dogs a ffected by encephalopathy and myositis, N. caninum has a structure and a life cycle similar to Toxoplasma gondii. Neosporosis is a cattle disease. Dog and some canids are known as definitive hosts of N. caninum. Clinically, neosporosis manifests by abortions in cows and nervous neonatal diseases in many domestic and wild mammals. The epidemiology of the disease is still poorly understood. However, N. caninum appears to be one of the most important causal agents of abortions in cattle in most countries. Furthermore, neosporosis could constitute a public health problem.
... For the horizontal transmission, the definitive hosts, dogs (McAllister et al., 1998; Basso et al., 2001) are important. The presence and the number of dogs on the farm as an important risk factor and strong association with herd seroprevalence or Neospora-related abortions are well documented (Sawada et al., 1998; Ould-Amrouche et al., 1999; Wouda et al., 1999; Mainar-Jaime et al., 1999; de Souza et al., 2002; Dijkstra et al., 2002; Hobson et al., 2004). The point source abortion outbreaks due to the presence of dogs have also been reported (Dijkstra et al., 2002; McAllister et al., 1996). ...
... The presence and the number of dogs on the farm as an important risk factor and strong association with herd seroprevalence or Neospora-related abortions are well documented (Sawada et al., 1998; Ould-Amrouche et al., 1999; Wouda et al., 1999; Mainar-Jaime et al., 1999; de Souza et al., 2002; Dijkstra et al., 2002; Hobson et al., 2004). The point source abortion outbreaks due to the presence of dogs have also been reported (Dijkstra et al., 2002; McAllister et al., 1996). Recently, coyotes have been identified as definitive hosts (Gondim et al., 2004) and they may contribute substantial horizontal transmission of Neospora in areas where these animals are common such as North America. ...
... This is not unexpected because all fetuses of Neospora infected cows may not be infected and all fetuses infected in utero may not be aborted; instead, many were born normal and healthy (Paré et al., 1996Paré et al., , 1997 Moen et al., 1998). However, Neospora abortions are more pronounced during outbreaks by point-source infection (Dijkstra et al., 2002; McAllister et al., 1996; McAllister et al., 2002) and subsequent years (Pfeiffer et al., 2002). Generally, dogs on the Neospora infected farms had a higher rate of antibody against Neospora and high association with the herd infection (Sawada et al., 1998; Wouda et al., 1999; de Souza et al., 2002). ...
Thesis (Ph.D.)--Chulalongkorn University, 2005 The aims of this study were (1) to identify N. caninum (NC) in the aborted fetuses and to establish an isolation guideline and (2) to investigate the impact of NC on the reproductive performance and abortion risk in dairy cows of NC-seropositive herds. NC tachyzoites were detected, by IHC, in the brain of one of 22 fetuses and its dam was NC seropositive by IFA. The other fetuses and their dams were seronegative. For isolation guideline, the brains of 4 seropositive pregnant cows and their calves, after parturition, were used for direct culture in vero cells and bioassay in hamsters (Mesocricetus auratus). Four groups (4 treated and 2 controls each) of hamsters were treated with the brain homogenates of 2 cows and their calves. All cows, calves and hamsters showed no clinical illness until they were euthanized. Selected tissues of cows, calves and hamsters were tested by HE, IHC and PCR. At calving, sera of 3 cows and precolostral blood of their calves were seronegative. The sera of one cow and its calf were seropositive (IFA titer of 1:100 each and ELISA value of 69.3% and 73.1% respectively). A tissue cyst was detected in the brain of this calf by IHC and Neospora DNA was also PCR-amplified but not from the brain of its dam. The parasites were not detected in the other tissues of all cows, calves and hamsters. Parasite DNA was also amplified from brains of two of four hamsters treated with the brain homogenates of IHC positive calf. The DNA was not amplified from the other dam-calf pairs and hamsters. Partial sequencing of the NC DNA showed the 99% identities of 225 bp with the reference sequence of NCl strain. It was designated as Thai-B1. Parasite isolation was not successful. It was concluded that vertical transmission may be much lower than previous reports, as evidenced by serology, IHC and PCR. Also chronically infected cows may have seronegative conversion and the antibody titers of their calves at parturition may be much lower than the other reports. The hamsters (M. auratus) may not be susceptible enough to N. caninum. Whether to use the isolation method in this guideline needs further clarification. This is the first report of Neospora-infection in aborted fetus and congenitally infected calf in Thailand. Holstein Friesian crossbred cows (total: 216) from 12 NC-seropositive farms in Nakhon Pathom were used to study the impact of Neospora infection on the reproductive performance. Blood samples were collected monthly for 10 months. The records of AI, calving and abortions were obtained from the Ratchaburi AI center and farm records. Herd seroprevalence was 12.9% (range 4.76 to 30%). Reproductive performances in seropositive and seronegative cows were the same (P > 0.05). But the performances were considerably lower then the other reports. Highly significant differences in the reproductive performance among herds were found (P = 0.0001 to 0.0005). The risk of abortion was also not associated with the Neospora seropositivity of the cows (RR = 2.25;95%CI = 0.64 to 7.9). It was concluded that in herds with relatively low seroprevalence, Neospora seropositivity had no impact on the reproductive performances of the dairy cows. The inferior performance of the cows and large variation among herds indicate the need for the check of management and/or other factors for the improvement. การศึกษานี้มีวัตถุประสงค์เพื่อ (1) ตรวจวินิจฉัยและยืนยันเชื้อโปรโตซัว N. caninum (NC) ในเนื้อเยื่อลูกโคแท้ง พร้อมทั้งกำหนดแนวทางวิธีการตรวจแยกเชื้อ และ (2) เพื่อสำรวจวิจัยผลกระทบของ NC ต่อสมรรถนะของระบบสืบพันธุ์ และประเมินความเสี่ยงการแท้งลูกของแม่โคนมในฝูงที่ติดเชื้อนี้ ตรวจพบ ทาชิซ้อยท์ ของเชื้อ NC โดยวิธี อิมมูโนฮิสโตเคมี ในสมองลูกโค 1 ตัวจากจำนวนลูกโคแท้ง 22 ตัว ลูกโคที่ตรวจพบ NC นี้แท้งจาก แม่โคที่ตรวจพบภูมิคุ้มต่อโรคนี้ ด้วยวิธี ไอเอฟเอ ส่วนแม่โค 21 ตัว และลูกตรวจไม่พบภูมิคุ้มต่อโรค การกำหนดแนวทางวิธีตรวจแยกเชื้อศึกษาจากแม่โค 4 ตัวที่พบภูมิคุ้มต่อโรค เนื้อเยื่อสมองของแม่โคและลูกหลังคลอด ใช้สำหรับการแยกเชื้อโดยเพาะเชื้อโดยตรงในเซลล์เฉพาะเลี้ยง วีโร และ วิธีฉีดเข้าหนูแฮมสเตอร์ (Mesocricetus auratus) หนู 4 กลุ่มทดลอง (ฉีด 4 ตัว ควบคุม 2 ตัว) ได้รับการฉีดเนื้อเยื่อสมองบดจากแม่โคและลูก 2 ตัว แม่โค ลูกโคและหนูทั้งหมดไม่พบอาการผิดปกติในระหว่างการศึกษาจนถึงวันฆ่าเพื่อ เก็บเนื้อเยื่อส่วนต่างๆ จากแม่โค ลูกโค และหนูไปศึกษาต่อโดยวิธีย้อมสี HE, IHC และตรวจ PCR ตัวอย่างเลือดแม่โคและลูกโคหลังคลอดก่อนกินนมน้ำเหลือง 3 คู่ตรวจไม่พบภูมิคุ้มต่อโรค แต่พบแม่โคและลูก 1 ตัว มีภูมิคุ้มต่อโรค (IFA) ที่ระดับ 1:100 และ อีไลซ่าที่ 69.3% และ 73.1% ตามลำดับ ผลการย้อมสี IHC ตรวจพบเชื้อปาราสิต ซิสต์เฉพาะในสมองลูกโคที่ตรวจพบภูมิคุ้มโรคแรกคลอด แต่ไม่พบในเนื้อเยื่ออื่นจากแม่โค ลูกโคและหนูแฮมสเตอร์ การยืนยันโดยวิธี PCR ในการตรวจดีเอ็นเอ ของนีโอสปอร่าไม่พบในสมองแม่โค แต่พบในสมองลูกโคที่ตรวจพบซิสต์ และสมองของหนูแฮมสเตอร์ 2 ใน 4 ตัว ที่ได้รับการฉีดสมองจากลูกโคตัวนี้ การศึกษานี้พบว่าดีเอ็นเอ NC มีความเหมือน 99% กับส่วน 225bp ของส่วนอ้างอิง NC1 และให้ชื่อใหม่ว่า Thai-B1 ไม่สามารถแยกเชื้อ NC โดยวิธีเพาะเชื้อโดยตรง การศึกษานี้สรุปได้ว่าอุบัติการติดเชื้อจากแม่ที่มีภูมิต่อ NC สู่ลูกในขณะอุ้มท้อง ต่ำกว่าในที่มีรายงานมาก่อน จากผลการศึกษาทางซีรั่มวิทยา IHC และ PCR นอกจากนี้แม่โคที่เคยตรวจพบภูมิคุ้มต่อโรค NC อาจให้ผลลบเมื่อตรวจก่อนคลอด มีผลทำให้ผลการตรวจภูมิคุ้มในลูกต่ำกว่ารายงานอื่น ผลการศึกษาพบว่าหนูแฮมสเตอร์ (M. auratus) อาจไม่ไวต่อการติดเชื้อต่อสเตรน Thai-B1 และวิธีการแยกเชื้อวิธีนั้นควรมีการศึกษาต่อไป รายงานนี้เป็นรายงานแรกที่พบการติดเชื้อจากแม่สู่ที่มีการติดเชื้อตามธรรมชาติลูกขณะอุ้มท้องในประเทศไทย การศึกษาผลกระทบต่อสมรรถนะการสืบพันธุ์ในฟาร์มโคนมที่ตรวจพบแม่โคมีภูมิคุ้มต่อ NC จำนวน 12 ฟาร์ม จำนวน 216 ตัว ที่มีโคนมพันธุ์ผสมโฮลสไตน์ 4-29 ตัวต่อฟาร์ม ในจังหวัดนครปฐมระหว่างเดือน มกราคม ถึง ตุลาคม พ.ศ.2547 เจาะเลือดแม่โคทุกตัวเดือนละครั้งติดต่อกันนาน 10 เดือน พร้อมเก็บบันทึกข้อมูลผสมเทียน การคลอด การแท้งลูก สภานภาพการติดเชื้อพบ 12.9% (พิสัย 5.9-30%) ผลการวิเคราะห์ข้อมูลไม่พบความแตกต่างทางสมรรถนะการสืบพันธุ์ระหว่างฟาร์มที่ศึกษา (P=0.0001และ P=0.0005)ไม่พบความเสี่ยงต่อการแท้งลูกในแม่โคที่มีภูมิคุ้มโรค (RR=2.25; 95%CI=0.64-7.9) สรุปได้ว่าการติดโรค NCมามีผลต่อสมรรถนะของการสืบพันธุ์ของโค การที่จะปรับให้สมรรถนะรบบสืบพันธุ์ที่ต่ำลงในฝูงโคนมให้ดีขึ้นนั้น ควรดูการจัดการฟาร์มและปัจจัยอื่นๆที่เกี่ยวข้อง
... the lack of correlation between N. caninum seropositivity of dam-daughter pairs, also suggests the occurrence of horizontal infection during year 5, as described in cattle (Dubey et al. 2017). Several studies in cows produced evidence that a recent horizontal infection usually preceded an outbreak of abortions (McAllister et al. 2000;Dijkstra et al. 2002), while abortions have been defined as epidemic if more than 10-12% of cows at risk abort within 6-8 weeks (Dubey and Lindsay 2006). The abortion incidence detected in the present study at year 5 during the elapsed period between scannings agrees with the mentioned definition. ...
... Although the point-source of the horizontal N. caninum infection is unknown, contamination of the concentrate mixed ration feed with oocysts is possibly the most likely origin, considering the high proportion of animals that became infected at year 5 in different paddocks. Other authors have previously mentioned contaminated mixed rations as the most suspected cause of epidemic outbreaks, both in dairy (Dijkstra et al. 2002;Huang et al. 2004;McAllister et al. 1996;Melendez et al. 2021;Yaeger et al. 1994) and beef cattle (McAllister et al. 2000). Grass or water faecal contamination by dogs present in the farm should not be ruled out, although fewer animals probably should have been infected. ...
This study describes for the first time an abortion outbreak caused by Neospora caninum in farmed red deer. During a 5-year period, farmed hinds, naturally mated, were regularly ultrasound monitored to detect reproductive losses over their gestation. During the 4 years previous to the outbreak, abortion rates ranged from 4.7 to 8.6% (average 6.5%), and serology for indirect diagnosis of neosporosis and toxoplasmosis was performed. At the fifth year, the abortion rate increased to 25.3%. During this outbreak, three aborted foetuses and their placentas were recovered and submitted to laboratory for etiological diagnosis. Blood samples were collected from the 81 hinds at the end of the gestational period and the seropositivity rate for N. caninum, Toxoplasma gondii, Brucella abortus, bovine viral diarrhoea virus and bovine alphaherpesvirus type 1 was 66.7%, 67.9%, 0.0%, 8.6% and 0.0%, respectively. Neospora caninum-seropositive hinds (OR = 5.7, P = 0.0271) and hinds with high antibody titres to N. caninum (OR = 7.4, P = 0.0130) were more likely to abort than seronegative hinds. In addition, N. caninum seropositivity rate in the aborted hinds was higher (OR = 5.4, P = 0.033) than the non-aborted hinds. No association was found between T. gondii nor BVDV-seropositivity and abortions. Typical protozoal histopathologic findings (necrotizing non suppurative encephalitis, meningitis, myocarditis, hepatitis, among others) were observed in all foetuses. Neospora caninum was immunolabelled by immunohistochemistry in several tissues from two foetuses, and infection was also confirmed in the three foetuses by serology and/or DNA detection. No other abortifacient agent was detected in the foetuses. Their dams showed high N. caninum antibody titres (≥ 6400). Serologic evidence and epidemiological data recorded suggested a point-source of N. caninum infection before the occurrence of the outbreak, probably related with contaminated feedstuff with oocysts. Moreover, the intensive production system with a high stocking rate could be also considered a factor which might have increased the risk of horizontal N. caninum infection in this herd.
... N. caninum has a heteroxenous life cycle consisting of two distinct modes of reproduction: an asexual reproduction, which occurs in intermediate hosts such as sheep, goats, cattle and others [1,13,[16][17][18]; and a sexual reproduction, which only occurs in canids such as dogs (Canis lupus familiaris) [19][20][21], coyotes (Canis latrans) [22], wolfs (Canis lupus) [23,24] and dingoes (Canis lupus dingo) [25]. Canids are the definitive host for this parasite, and they may also be affected clinically [26][27][28][29]. ...
... Therefore, it seems prudent to exclude congenitally infected calves as replacement stock, as suggested previously [68], in order to decrease the future risk of abortion in the herd and to discontinue vertical transmission over the generations. This aspect has been highlighted by many authors who point out that the vertical route is the main transmission route of N. caninum in cattle, estimated at an average of 75 to 90.0%, without forgetting the risk of horizontal transmission due to ingestion by the cattle of oocysts eliminated with faeces by the definitive hosts (dogs, dingoes, coyotes, wolfs) [18,19,21]. ...
Neosporosis is recognized as one of the major causes of bovine abortion worldwide. Canids are the main definitive host for this parasite and the presence of dogs in the farm is an important factor for the Neospora caninum infection in bovines. Since, in the province of Lecce, located in the Apulia region of Southern Italy, there are no studies showing the presence of the infection in farm animals, the objective was to perform a serological evaluation for anti-N. caninumantibodiesin serum from 706 dairy cattle and 21 farm dogs located in 40 farms uniformlydistributed over the territory.The presence of N. caninum infection was confirmed in 90.0% (36/40) of the 40 farms examined. The results obtained on all serum samples by an enzyme-linked immunosorbent assay (ID Screen® Neospora caninum competition ELISA kit) for anti-N. caninumantibodies showed a seropositivity rate of 21.1% (149/706) among dairy cows, with a statistically significant higher percentage of positive subjects in the animals over two years old and a positivity rate of 42.9% (9/21) in tested dogs. The obtained data confirmed the presence of neosporosis even in the Lecce area, where it could therefore represent an important cause of abortion and economic losses.
... pregnant) cattle to oocysts shortly before the abortion storm occurs. There is some circumstantial evidence to support this view (McAllister et al. 2000 ;Dijkstra et al. 2002 ;Björkman et al. 2003) but it is not clear how often post-natal transmission occurs and how frequently it results in abortion. ...
... There is very little data available on what happens in adult cattle in pregnancies subsequent to that during which they were exposed to oocysts. In one study where there was good evidence that a herd had been exposed to oocysts (Dijkstra et al. 2002) an analysis of the subsequent offspring (i.e. those conceived after exposure to oocysts) suggested that endogenous transplacental transmission had occurred. ...
Vertical transmission of the protozoan parasite, Neospora caninum is highly efficient and can take two forms - endogenous transplacental transmission resulting from activation of the quiescent bradyzoite stage during pregnancy or exogenous transplacental transmission resulting from ingestion of oocysts during pregnancy. Calves born carrying infection derived from either endogenous or exogenous transplacental transmission are capable of infecting their offspring when they start to breed. This review considers firstly the frequency with which exogenous and endogenous transmission occur, secondly the role of the immune response in controlling N. caninum infection and thirdly how the parasite persists in an immune-competent host and is re-activated during pregnancy.
... The presence of a farm dog is a risk factor for the occurrence of N. caninum-associated abortions in dairy herds (Paré et al., 1998;Bartels et al., 1999). Abortion outbreaks following post-natal N. caninum infections in cattle occurred within 1.5 years after the introduction of a new dog or the birth of puppies on the farm (Dijkstra et al., 2002). However, the mechanisms of transmission of N. caninum on the farm are still unclear. ...
... All herds had experienced an episode of increased incidence of N. caninum associated abortions in cattle. On all farms, a new dog had been introduced by purchase or by birth within a period of 1.5 years prior to the onset of the first indication of N. caninum infection (Dijkstra et al., 2002). On average 48% of the animals in the 12 post-natally infected herds were seropositive for N. caninum, ranging per herd from 27 to 68%. ...
Twelve dairy herds with evidence of post-natal infection with Neospora caninum were compared with 21 control herds with no evidence of post-natal infection. On the former farms, dogs consumed placenta or licked uterine discharge in 75 and 67% of the farms, respectively, while on control farms these activities occurred in 38 and 24% of the farms, respectively. On all control farms and all but three post-natally infected farms the dogs were fed colostrum or milk. Defecation of dogs on the feeding alley was observed in 92% of the post-natally infected farms and in 24% of the control farms. The same trend was observed for defecation of dogs in grass silage, in 75% of the post-natally infected farms and in 19% of the control farms; and in corn silage, in 50% of the post-natally infected farms and in 10% of the control farms. Consumption of placenta, material of aborted foetuses or uterine discharge in combination with defecation on the feeding alley, storage of grass or corn silage was observed in 19% of the control farms and in 75% of the post-natally infected farms. This study supports the hypothesis that farm dogs may become infected by foetal fluids or placental material of infected cattle, and may subsequently cause a post-natal infection of cattle in the herd by shedding oocysts.
... On the contrary, the horizontal transmission process consists of within-herd level and outside-herd level (external source of infection). Potential sources of within-herd transmission include pooled colostrum or milk from infected cattle [23] and infected placenta or amniotic fluid or oocyst-contaminated feed which is therefore described as age-dependent infection force with a prevalence dependent factor ζ. ere is evidence suggesting that cattle may be infected by a definitive host, a dog or possibly other canids [24], and this external source of infection is denoted by a constant per-capita force σ. ...
Neospora caninum (N. caninum) infection, one of the major causes of abortions in dairy cattle, has brought a huge loss to farmers worldwide. In this study, we develop a six-compartment susceptible-infected model of N. caninum transmission which is later reduced to a two-equation system. Potential controls including medication, test-and-cull, and vaccination are proposed and analyzed, and the corresponding reproduction numbers are derived. The conditions for the global stabilities of disease-free and endemic equilibria are investigated with analytical solutions and geometric approach. Furthermore, uncertainty and sensitivity analysis shows that three control strategies are effective towards the varied environment, whereas the effectiveness of each measure highly depends on parameters related to control actions. Dynamics of reproduction numbers illustrate that disease elimination can be achieved by three types of controls: (1) adopting medication with medicine efficacy higher than 0.4 to prevent vertical transmission, (2) implementing test-and-cull with culling coverage larger than 0.3, and (3) taking vaccine with coverage larger than 0.1. Numerical results suggest that preventive measures should at least include the prevention of access of other hosts, such as dogs, to cattle; otherwise, these control measures will lose effectiveness. Our presented study provides guidance for decision-making on N. caninum infected farm management.
... (iii) The farm is in good management and cattle are well isolated from other potential hosts outside. Thus, horizontal infection due to hosts outside the herd [8] is not included. Dynamics of the disease-infected dairy cattle with vaccination control are described by the following equations (transmission flow diagram is illustrated in Fig. 1): ...
The transmission of production-limiting disease in farm, such as Neosporosis and Johne's disease, has brought a huge loss worldwide due to reproductive failure. This paper aims to provide a modeling framework for controlling the disease and investigating the spread dynamics of Neospora caninum-infected dairy as a case study. In particular, a dynamic model for production-limiting disease transmission in the farm is proposed. It incorporates the vertical and horizontal transmission routes and two vaccines. The threshold parameter, basic reproduction number 0, is derived and qualitatively used to explore the stability of the equilibria. Global stability of the disease-free and endemic equilibria is investigated using the comparison theorem or geometric approach. On the case study of Neospora caninum-infected dairy in Switzerland, sensitivity analysis of all involved parameters with respect to the basic reproduction number 0 has been performed. Through Pontryagin's maximum principle, the optimal control problem is discussed to determine the optimal vaccination coverage rate while minimizing the number of infected individuals and control cost at the same time. Moreover, numerical simulations are performed to support the analytical findings. The present study provides useful information on the understanding of production-limiting disease prevention on a farm.
... Our knowledge on the transmission of the parasite in cattle populations was enhanced by an understanding of the relative importance of vertical [33][34][35][36][37] versus post-natal transmission [38][39][40][41][42][43], often occurring simultaneously in the same cattle herd [44]. Based on that a better understanding of the risk factors contributing to N. caninum abortions was achieved [45][46][47], and mitigation strategies suggested, such as, in one study, the use of beef semen [48]. ...
Background:
Neospora caninum has been recognised world-wide, first as a disease of dogs, then as an important cause of abortions in cattle for the past thirty years. Over that time period, there have been improvements in the diagnosis of infection and abortion, new tests have been developed and validated, and it is timely to review progress to date.
Methods:
Bibliometric methods were used to identify major trends and research topics present in the published literature on N. caninum. The tools used were SWIFT-Review, VOSviewer and SciMAT, along with the published papers found in the MEDLINE, Dimensions and Web of Science databases. A systematic review of the published Neospora literature (n = 2933) was also carried out via MEDLINE and systematically appraised for publications relevant to the pathogenesis, pathology and diagnosis of Neospora abortions.
Results:
A total of 92 publications were included in the final analysis and grouped into four main time periods. In these four different time periods, the main research themes were "dogs", "abortion", "seroprevalence" and "infection". Diagnostics, including PCR, dominated the first two time periods, with an increased focus on transmission and abortions, and its risk factors in cattle.
Conclusions:
Longitudinal analyses indicated that the main themes were consistently investigated over the last 30 years through a wide range of studies, with evolving emphasis initially on dogs and diagnostic test development, followed by application to cattle, the identification of the risk factors leading to abortion, and in the latter time periods, an understanding of the immunity and a search for vaccines.
... Horizontal transmission in cattle is usually less than 5% per year (Chanlun et al., 2007;Davison et al., 1999;Hietala and Thurmond, 1999). However, in some cases, this rate can be up to 47% within 6 months (Dijkstra et al., 2002;More et al., 2009). ...
Neospora caninum is an obligate intracellular coccidian parasite, which can infect various animal species. The parasite has a two-host life cycle and exists in three stages. N. caninum can survive and disseminate among animals through horizontal and vertical transmissions. Prevalence of N. caninum infection in animals is different from species to species, from location to location. In adult animals, neosporosis causes abortion, which mostly occurs at mid-gestation and is the only known symptom so far. Pregnancy loss in positive cattle can be up to 44%. Offspring born to infected mothers may be free of disease, subclinically infected or clinically infected. Most clinical symptoms are related to neurological signs and difficulty in locomotion.
... The seroprevalence of N. caninum in rural areas has been reported to range from 2.8% in beef cattle in New Zealand (TENNENT-BROWN et al., 2000) to 76.9% in dairy cattle in Colombia (CEDEÑO & BENAVIDES, 2013). Dijkstra et al., (2002) reported that when a young dog is introduced to a farm or upon the birth of the dog's offspring on the farm, the risk of bovine abortion increases. The presence of Cunha Filho et al. dogs in bovine breeding farms was considered an important risk factor for the horizontal transmission of N. caninum and subsequent abortion in different countries (PARÉ et al., 1998). ...
This study was conducted at a beef cattle breeding farm in the far southern region of Brazil. The birth of a calf with unilateral corneal opacity was immediately reported to the Laboratory of Parasitology, in the Universidade Federal de Pelotas, Rio Grande do Sul, Brazil; blood was collected from the cow and calf before colostrum intake. The umbilical cords from this calf and from six other healthy animals were collected. Serological examination, utilizing an indirect fluorescent antibody test, was done using a cut-off point of 1:100. Polymerase chain reaction (PCR) was also performed using the umbilical cord samples. Serological tests showed that the calf was positive for Neospora caninum at birth, with a titer of 1:1600; a titer of 1:3200 was reported in the dam. PCR, using umbilical cord tissue from the affected animal, was positive for the presence of this parasite, and the molecular identity of the amplified product was confirmed by sequencing. Therefore, the detection of N. caninum DNA in the umbilical cord represents a novel alternative test for the diagnosis of this parasitic infection in newborn calves that are clinically suspected to have neosporosis.
... Transplacental transmission has been induced experimentally in dogs (Cole et al., 1995;Dubey and Lindsay, 1989) and reported in naturally infected dogs Dubey et al., 2005). To maintain continuous parasite life cycle in farm cattle; it is believed that both horizontal and vertical transmission routes are necessary in maintaining infection level (Dijkstra et al., 2002b;Williams et al., 2009). However, endogenous infection efficiencies in Chapter One 6 dairy herds have been reported to be as high as 78-95 % (Davison et al., 1999b;Paré et al., 1997) and it is considered to be the main transmission route of N. caninum (Dubey et al., 2007;Williams et al., 2009). ...
Toxoplasma gondii and Neospora caninum are closely related obligatory intracellular apicomplexan parasites that invade and multiply in almost all mammalian host cells. They cause disease in immunocompromised animals, abortion in the intermediates host and great economic losses to the farming industry. However, there are several biological differences between these parasites, including host range, zoonotic capacity, transmission, virulence and definitive host. What causes these biological differences is not well understood. To fully understand these biological differences, the host-parasite interactions of these parasites have been investigated in this study using several different approaches at the molecular level.
Due to the importance of protein-protein interactions (PPIs) and multiple protein complexes (MPCs) in host-parasite interactions, blue native polyacrylamide gel electrophoresis (BN-PAGE) combined with liquid chromatography tandem mass spectrometry (LC MS/MS) was used to study T. gondii and N. caninum tachyzoites. Several interesting complexes were identified in N. caninum tachyzoites and include mitochondrial complexes, proteasome, glideosome and moving junction molecules that play an important role in the physiology and invasion of host cells. In addition, in T. gondii the microneme MIC1/6 complex was found migrated and/or co-associated with the important surface antigen glycoprotein SAG1, which is critical in the initial interaction with host surface peptidoglycan.
In order to understand the direct interactions between parasite secretory proteins such as dense granule proteins (GRA2 and GRA7) and host cell proteins; a pull-down assay has been used to elucidate the binding partners of expressed recombinant GRA2 and GRA7 in both parasites within the host cell lysate. Several methods were applied to purify the recombinant GRA proteins such as affinity chromatography using nickel or cobalt, salting-out, denaturing buffer using urea and reverse phase HPLC. TgGRA2 was successfully purified by HPLC and attempts have been made to study its role in host-parasite interactions using a pull-down assay.
Since these parasites secrete an array of secretory proteins, including kinases, to manipulate host cell responses; phosphopeptide enrichment, combined with LC MS/MS has been used to study the global response in the host signalling pathway through protein phosphorylation and signal transduction in response to infection with T. gondii and N. caninum. Three important differences were identified; about one-third of the phosphoproteomes of the host cell in response to infection by T. gondii and N. caninum was different. Approximately 21 % of the phospho-motifs were found differentially enriched between host cells infected with T. gondii compared to N. caninum infection and finally the pathway analysis showed that a few pathways were differentially enriched between infections with these parasites, such as glycolysis/gluconeogenesis and mTOR signalling pathway in infection with T. gondiibut not with N. caninum. The differences in the host cell phosphoproteome indicated that these parasites interact with the host cell differently.
As a means of understanding the broader host response to infection with these parasites at the systems biology level, integrated data analyses were performed on quantitative data from the transcriptome, proteome and phosphoproteome of host cells infected with the two parasites. Data analyses showed that host cells produce more proteins in response to infection with T. gondii than with N. caninum after 36 hours post infection (p.i.). In addition, data analysis showed that T. gondii inhibits apoptosis and acute inflammatory responses more when compared to N. caninum.
Overall, the results presented in this thesis have provided new insights into the biological differences between T. gondii and N. caninum. Several interesting differences in host-parasite interactions at both the qualitative and quantitative levels were identified. These interactions are related to the virulence and transmission strategy of the parasites and so are potentially associated with the biological differences between these parasites.
... All 8 farms reported the introduction of a new farm dog within a period of 1.5 y before the first indication of N. caninum infection (either a N. caninum abortion or N. caninum infected calf). As there was evidence in all herds of vertical transmission of N. caninum for years, it was hypothesized that the newly introduced (probably naïve) dog was infected with N. caninum through placental (or other) material from already infected cattle and that it subsequently transmitted the infection to other cattle by shedding oocysts (113). However, there were no uninfected farms in this small study; therefore, it is unknown whether a randomly selected group of uninfected dairy farms would also have had new farm dogs introduced within the past 1.5 y, or whether the 8 farms are representative of typical management seen in the dairy industry in The Netherlands or Canada. ...
Neospora caninum is one of the most important causes of abortion in cows. The occurrence of N. caninum infection in beef and dairy cattle has been reported worldwide, and in most provinces in Canada. The objective of this review is to summarize our current understanding of N. caninum in dairy and beef cattle for Canadian bovine practitioners. The review covers the life cycle of the agent, its mechanisms of transmission, clinical signs, and tests for diagnosing the infection. Data on the prevalence of the infection in Canadian dairy and beef cattle are reviewed and briefly compared with estimates from other parts of the world. Most importantly for Canadian bovine practitioners, the impacts of the infection, risk factors for its occurrence, and methods of control are also discussed. By reviewing the scientific literature on N. caninum from a Canadian perspective, culling decisions based on the interpretation of diagnostic tests are more effectively made in the control of N. caninum-associated disease.
... Post-natal bovine infection through oocysts shed by dogs (McAllister et al., 1998) or perhaps other, so far unidentified, definitive hosts appears to be likely (McAllister et al., 2000;Schares et al., 2002a). In herds with epidemic abortion, point source exposure to N. caninum, e.g. through oocyst-contaminated fodder or drinking water, is regarded as the most probable cause of infection (McAllister et al., 2000;Dijkstra et al., 2002;Schares et al., 2002a). ...
Objective: Neospora caninum belongs to the most frequently diagnosed infectious causes of bovine abortion. In cattle herds, infections with N. caninum may result in permanently increased abortion rates or abortion outbreaks. The aims of the here summarized studies were to obtain an overview over the distribution of bovine N. caninum infections in the German state of Rhineland-Palatinate and to identify putative risk factors for the introduction of the infection into herds. Material and methods: In the year 2000 90% (n = 3260) of the dairy herds of the state of Rhineland-Palatinate were examined by a bulk milk ELISA. Results: Clear regional differences were observed. In the districts and cities located in the south of Rhineland-Palatinate more than 15% of the herds were tested positive while in the north-western districts the prevalence was partially below 5%. A risk factor analysis to which more than 1200 farmers contributed was conducted during the same period of time. It indicates that farm dogs represent the most important risk factor. However, also the density of dogs kept in the municipality of farm location appeared as a risk factor for herds to be bulk milk positive. Conclusions and clinical relevance: The results of the summarized studies provide evidence that, in addition to farm dogs, also dogs kept in the surroundings of farms represent a source for the introduction of N. caninum infections into cattle herds. The observations can explain why N. caninum associated abortions also occur on German farms that do not keep dogs.
... Uso de vedações na exploração que não permitam a entrada de outros animais, principalmente cães (Dubey et al, 2007). Este é um factor bastante relevante, principalmente porque os cães recém-introduzidos excretam uma maior quantidade de oocistos, podendo levar a novos surtos em explorações com neosporose endémica (Dijkstra et al, 2002b). ...
... These oocysts sporulate in the environment and can infect cattle through oral exposure (horizontal transmission) (Dubey and Lindsay, 1996). Therefore, horizontal transmission between definitive and intermediate hosts is associated with a predator-prey lifecycle and often related to the presence on farm of dogs (Dijkstra et al., 2002) and wild carnivores (Wapenaar et al., 2006;Dubey et al., 2011) having access to infected tissues and abortion material. In contrast, vertical transmission (from dam to fetus) involves other herd management risk factors such as the purchase of replacement heifers and control measures such as culling of infected cows (Dubey et al., 2007). ...
... The higher seroprevalence of N. caninum in dogs from N. caninum positive dairies gives us a clue about the epidemiological association between dogs and cattle. Previous studies have demonstrated that the presence of dogs on cattle farms, can play an important role in the seropositivity and bovine abortion (Bartels et al., 1999;Dijkstra et al., 2002b;Schares et al., 2003). Our finding of a significant difference of prevalence between male and female dogs was not expected based on previous studies (Trees et al., 1993;Barber et al., 1997;Sawada et al., 1998). ...
... The observed relationship between prolonged presence of dogs on farm and an increased seroprevalence in cattle is similar to reports from Germany (Schares et al., 2004) and Canada (Haddad et al., 2005). The probability that the farm environment, utensils and feed or water will be contaminated with N. caninum oocyst would be expected to increase with presence of dogs, as they are the most usual definitive host of N. caninum and numerous studies have provided evidence of the role played by dogs in exacerbating transmission (Corbellini et al., 2006;Dijkstra et al., 2002;Ghalmi et al., 2012;Machado et al., 2011;Otranto et al., 2003;Van Leeuwen et al., 2010). ...
A cross-sectional study of Neospora caninum infection was conducted in major milksheds of Ethiopia. Cattle (n=2334) from 273 farms were bled and the sera screened for antibodies against N. caninum using a commercial ELISA kit. Herd and individual animal level data were collected from farm records and a semi-structured questionnaire format. The overall animal level seroprevalence was 13.3%, while the prevalence at farm level was 39.6%. In urban and peri-urban smallholder dairy farms, the seroprevalence was 14.9%, while 12.9% and 9.8% reactors were found among commercial dairy farms and breeding cattle, respectively. At farm level, 35.7% of urban and peri-urban farms, 47.5% of the commercial farms and five of the breeding farms were found to have at least one infected animal. Purchased cows (OR: 2.3) and cows with history of maternal reproductive disorders (OR: 2.1) were associated with seropositivity at the individual animal level. Crossbred cattle (Holstein-Friesian crossed with indigenous zebu) were associated with lower risk than pure breeds (OR: 0.6). A trend of prevalence increment was observed for large herd sizes (OR: 1.8). Other factors that were associated with seropositivity were: presence of farm dogs for more than 5 years (OR: 1.9), access to farm by wild carnivores (OR: 3.1) and compromised farm hygienic status (OR: 3.4). Abortion, retention of foetal membrane and metritis were the most frequently reported clinical reproductive disorders among seropositive cattle. Together, these finding indicate that N. caninum infection is highly prevalent, widely distributed and clinically important in dairy and breeding cattle of Ethiopia. N. caninum should be considered an important infectious cause of reproductive disorders in Ethiopian cattle, and the risk factors for exposure identified here should be used as basis for implementing control measures that could limit the transmission of this infection.
... Horizontal transmission in cattle is usually less than 5% per year (Chanlun et al., 2007;Davison et al., 1999;Hietala and Thurmond, 1999). However, in some cases, this rate can be up to 47% within 6 months (Dijkstra et al., 2002;More et al., 2009). ...
TÓM TẮT Neospora caninum là một ký sinh trùng hình cầu sống ký sinh bắt buộc trong tế bào, có thể gây bệnh ở rất nhiều loài động vật. Trong vòng đời của mình, N. caninum cần một vật chủ trung gian và một vật chủ cuối cùng. Loài ký sinh trùng này tồn tại ở ba dạng và lưu truyền giữa các động vật thông qua hai con đường: lây truyền dọc từ mẹ sang con và lây truyền chéo giữa các cá thể. Tỷ lệ nhiễm N. caninum khác nhau ở các loài động vật và khu vực sinh sống. Ở động vật trưởng thành, bệnh do N. caninum gây ra có thể làm sẩy thai chủ yếu vào giữa thai kỳ và đó cũng là triệu chứng duy nhất được biết cho đến nay. Tỷ lệ sẩy thai ở bò có thể lên đến 44%. Những con non sinh ra từ mẹ bị nhiễm bệnh có thể không bị bệnh, hoặc bị bệnh nhưng không có triệu chứng hoặc thể hiện một số triệu chứng về thần kinh và gặp khó khăn khi vận động. Từ khóa: Dịch tễ học, Neospora caninum. SUMMARY Neospora caninum is an obligate intracellular coccidian parasite, which can infect various animal species. The parasite has a two-host life cycle and exists in three stages. N. caninum can survive and disseminate among animals through horizontal and vertical transmissions. Prevalence of N. caninum infection in animals is different from species to species, from location to location. In adult animals, neosporosis causes abortion, which mostly occurs at mid-gestation and is the only known symptom so far. Pregnancy loss in positive cattle can be up to 44%. Offspring born to infected mothers may be free of disease, subclinically infected or clinically infected. Most clinical symptoms are related to neurological signs and difficulty in locomotion.
... A significant association between the presence of dogs and the prevalence of anti-N.caninum antibodies in cattle was observed (Wouda et al., 1999; Dijkstra et al., 2002). Here, farm dogs were from an area where more than 10% of the herds have within-herd prevalence between 50% and 100% (Bartels et al., 2006). ...
In a previous study, farm and stray dogs were considered potential high risk populations of Neospora caninum infection in Spain. Consequently, we decided to investigate the significance of N. caninum infection in these populations. Specific antibodies were detected in 120 out of 275 dog sera (43.6%), with titres ranging from 1:50 to 1:800. Differences in seroprevalence between farm (47.5%, 67/141) and stray (39.5%, 53/134) dogs were not significant (P>0.05; χ(2) test), but farm dogs showed significantly higher titres (P<0.01; Student's t-test). N. caninum seroprevalence in farm dogs was associated with increasing age (P<0.01; χ(2) test) and dogs with free access to the farm were more likely to be seropositive than controlled-dogs (P<0.05; χ(2) test). The presence of anti-N. caninum antibodies was more often detected in dogs from farms with 5-20% N. caninum within-herd seroprevalence (56.9%, 37/65) than those from farms with 0-5% seroprevalence (38%, 23/60) (P<0.05; χ(2) test). We microscopically observed N. caninum-like oocysts in the faeces from one farm dog, but the number of oocysts was very low, and the aetiology could not be confirmed. Also, parasite isolation was attempted from fresh neural tissue from stray dogs but was unsuccessful.
... Uma grande variedade de carnívoros silvestres já foram diagnosticados como soropositivos para N. caninum no Brasil e no mundo (GONDIM et al., 2004; CAÑON-FRANCO et al., 2004; VITALIANO et al., 2004; HAMILTON et al., 2005) Sartor et al., (2005) relataram que, através de levantamentos soroepidemiológicos, o N. caninum está amplamente distribuído no rebanho bovino brasileiro, com freqüências variando entre 8,06% (AGUIAR et al., 2006) a 87,5% (MUNHOZ et al., 2002). Andreotti et al., (2006) DIJKSTRA et al., 2002). ...
Neospora caninum é um protozoário do filo Apicomplexa que causa infecções associadas com aborto, mortalidade neonatal e alterações neurológicas em várias espécies animais. O cão desempenha papel fundamental na epidemiologia da neosporose por ser o hospedeiro definitivo deste protozoário. A prevalência de anticorpos para este protozoário em cães tem sido avaliada em vários países, inclusive no Brasil, com índices que variam de 4,8% a 45%. O presente trabalho objetivou verificar a prevalência de anticorpos classe IgG para Neospora caninum em cães e os fatores de risco na área urbana do município de Porto Alegre- RS, utilizando a Técnica de Imunofluorescência Indireta (RIFI) e aplicação de questionário epidemiológico com os responsáveis pelos animai. Os animais foram divididos em três grupos, animais domiciliados, errantes e de criatórios comerciais. A freqüência de anticorpos foi de 13,84% (36/260) de amostras positivas nas 260 amostras analisadas. Os títulos sorológicos observados variaram de 50 (44%) a 3200 (3%). Os dados obtidos no questionário foram analisados pelo Teste Exato de Fisher, e observou-se associação entre a positividade e os fatores alimentação e acesso a rua, com maior positividade para os animais que tinham acesso a rua (p<0.001) e recebiam alimentados com comida caseira. Os fatores idade, sexo e contato direto com outros cães não apresentaram diferença significativa em relação à positividade dos animais. Este estudo demonstra que o N. caninum está presente em cães da área urbana de Porto Alegre, necessitando de mais estudos nessa população que esclareçam os fatores de risco ao protozoário. Neospora caninum is a protozoan of phylum Apicomplexa which causes infections associated with abortion, neonatal mortality and neurological changes in several animal species. Dogs play key role in the epidemiology of neosporosis for being the definitive host of this protozoan. The prevalence of antibodies to this protozoan in dogs has been assessed in several countries, including Brazil, with rates ranging from 4.8% to 45%. This work had as its main objective to verify the prevalence of IgG class antibodies to Neospora caninum in dogs and the risk factors in the urban area of the municipality of Porto Alegre-RS using the Indirect Fluorescent Antibody Test (IFAT) and applying an epidemiological questionnaire with those responsible for the animals. Animals were divided into three groups, domestic (pets) and wandering animals and those from commercial breeders. The frequency of antibodies was 13.84% (36/260) of positive samples in 260 samples which were analyzed. The serological titles observed varied from 50 (44%) to 3200 (3%). The data obtained in the questionnaire were analyzed by Fisher Exact Test, and some association between the positivity of IFAT and factors such as food and access to the street were observed. There was greater positivity for animals which had access to street (p <0,001) and were fed with homemade food. Factors such as age, sex and direct contact with other animals have not showed any significant difference in relation to the positivity of the animals. This study demonstrates that Neospora caninum is present in dogs of the urban area of Porto Alegre which requires more studies in such population to clarify the risk factors to the protozoan.
... Alternatively, these discrepancies may be due to farm management practices, since in Argentina many dogs are present in most farms which could favor oocyst ingestion by cattle and therefore increase horizontal transmission. Furthermore, the high seroprevalence to S. cruzi antigen and efficient horizontal transmission evidenced in this study suggest frequent contamination of pastures with dog feces, which is a risk factor for N. caninum infection (Dijkstra et al. 2002;Moore et al. 2002). Estimation of N. caninum vertical transmission in farm 2 was 29%, similar to that reported by Moré et al. (2009) in dairy calves using the same diagnostic technique and cutoff titer. ...
Sarcocystis sp. and Neospora caninum infections affect cattle worldwide causing important economic losses. The objective of the present study was to trace serologic profiles for Sarcocystis sp. and N. caninum in naturally infected beef calves and analyze their relationship with transmission routes and productive performance. Samples were collected in two cow-calf operations located in Buenos Aires province, Argentina. In farm 1, 43 calves were bled and weighed three times. In farm 2, 69 calves were bled and weighed six times. Sarcocystis sp. and N. caninum immunofluorescence antibody test (IFAT) titers were averaged for each sampling point in order to trace serologic profiles for each infection. Categories were created to evaluate differences in daily weight gain. For S. cruzi antigen, animals were separated in a low-titer (< or = 200) and high-titer group (>200); for N. caninum, animals were grouped as infected and uninfected. Sarcocystis sp. antibody titer as well as the number of infected animals increased gradually over time in both farms. In farm 2 the low-titer group had significantly higher daily weight gain than the high-titer group. For N. caninum 44% (farm 1) and 65% (farm 2) of calves were considered infected, and the serological profile was horizontal or decreasing over time. However, seroprevalence increased in both farms and vertical and horizontal transmission frequency were estimated between 18.5%-29% and 22-25.5%, respectively. No differences were detected in daily weight gain between N. caninum groups from both farms. This is the first report of serological profiles for Sarcocystis sp. and N. caninum by IFAT in naturally infected beef calves and their relationship to different transmission routes and productive performance.
... Exposure of cows to faeces of definitive hosts could be reduced by minimizing the number of dogs (and other suspected intermediate hosts, e.g. other canids) in the herd, covering feeds and commodities to prevent contamination by dog faeces (Baillargeon et al., 2001; Dijkstra et al., 2002b; McAllister et al., 2000; McAllister et al., 2005). There is no drug or chemotherapy available for treatment of bovine N. caninum infection or to prevent transmission of the parasite from an infected dam to her offspring. ...
The protozoan parasite Neospora caninum is causing bovine abortion worldwide. The overall aim of this thesis was to gain a better understanding about N. caninum infection in dairy cattle in Thailand both at the individual animal and the herd level. Specifically, the aims were to investigate variations of N. caninum antibodies in milk of individual cows during lactation, to demonstrate the use of bulk milk antibody testing and its application, and to characterize N. caninum dynamics of infection in Thai dairy herds. The thesis is based on four separate studies.
The levels of N. caninum antibodies in milk of 15 infected cows varied considerably during 18 months although they were consistently considered positive. Cows of all lactation groups had a higher milk antibody at calving compared to at later months after calving, but the only significant difference was in the first lactation. Serum and milk antibody levels were always lower in first lactation than in second and later lactations. The results showed that individual milk can be an alternative material to demonstrate presence of N. caninum antibodies in lactating cows.
The bulk milk antibody levels in a cross-sectional sample of 11 herds ranged between 0.04 and 0.89 and the seroprevalences varied between 0% and 46%. Herds with higher bulk milk antibody levels showed a trend of higher portion of seropositive cows although there was no strong relationship between the bulk milk antibody level and the within-herd seroprevalence. Forty-six percent of the 220 bulk milk samples from nine milk collection centres were judged positive and the herd prevalence varied between milk collection centres.
Repeated bulk milk antibody testing of 418 dairy herds was evaluated and the herd N. caninum status was established at three consecutive samplings during one year. Herd status at either of the first two samplings was used to predict herd status at the last sampling, and was also interpreted in combinations. Using combinations gave higher predictability of a herd’s Neospora status than a single test. One hundred and thirty-six were considered negative, and one hundred and thirty-four herds were positive throughout the study. It was concluded that repeated bulk milk testing at regular intervals provided better information about herd N. caninum-antibody status than a single test. The results also showed that the infection is prevalent in northeast Thailand, but that a herd can keep a negative infection status.
When 11 dairy herds were investigated repeatedly during four years, the overall percentage of antibody-positive cattle was constant and varied only between 10% and 13%. However, the within-herd seroprevalence differed substantially between herds. Vertical transmission, i.e. from dam to calf, was the most frequent route of transmission. The proportions of individual animals that changed from being seronegative to seropositive and from being seropositive to seronegative between the years were 3.9-4.6% and 19-39%, respectively, although most animals had consistent serological status throughout the study. Some herds can thus keep free from N. caninum infection without farmers taking control measures.
... The main transmission route in cattle is vertical, i.e. by transmission of the parasite from the cow to her foetus during gestation. In addition, horizontal transmission may occur, and refers to cattle being infected postnatally by ingestion of oocysts excreted from a definitive host (McAllister et al., 2000; Dijkstra et al., 2002). Currently, dogs and coyotes are the only species verified as being definitive hosts of the parasite, and presence of dogs at the farm has been identified as an important risk factor associated with Neospora caninum related abortions as well as high prevalence (Bartels, Wouda & Schukken, 1999; Mainar-Jaime et al., 1999). ...
This thesis deals with aspects of the epidemiology of bovine viral diarrhoea virus (BVDV) of relevance to control, with particular focus on the situation in Peruvian smallholder dairy farms. In addition, the importance of Neospora caninum and bovine herpesvirus type 1 (BHV-1) is addressed, as these are important differential diagnoses to BVDV.
The prevalence of BVDV and BHV-1 was studied in smallholder dairy farms in a rural area. Using bulk tank milk testing for detection of antibodies it was shown that the prevalence of active BVDV infection was low, and that a large proportion of the herds were free from BHV-1. A study of the BVDV situation in the major dairy region in the country demonstrated a very high level of exposure to BVDV. Individual testing of young stock indicated, however, that many herds might be cleared from BVDV without intervention,
and that a long-term reduction in prevalence can be achieved as long as adequate attention is given to systematic measures aimed at preventing re-introduction of infection.
An endemic abortion problem in a dairy herd with concurrent infections with Neospora caninum and BVDV was investigated. Using a prospective seroepidemiological approach it was possible to estimate the magnitude of associations between the infections and risk of abortion, and to demonstrate that Neospora caninum infection significantly affected the risk within the herd. Evidence of active BVDV infection, on the other hand, was not associated with abortions.
The phylogenetic analysis of BVDV strains isolated from animals detected as persistently infected, demonstrated that all belonged to genotype 1, subtype 1b. The genetic similarity with previously described strains reflected the role of livestock trade for the diversity of BVDV. Imported livestock is the probable source of BVDV strains circulating in the country, and this was supported by the phylogenetic analysis.
Finally, it was demonstrated that a molecular epidemiological approach might be used to trace routes of transmission, and to identify and prevent risky behaviour.
... Furthermore, the age distribution of positive cases can be helpful for the interpretation of test results. In particular, the presence of age clusters with a high seroprevalence has been shown to indicate post-natal infection of these age groups by a point source exposure (Dijkstra et al., 2001(Dijkstra et al., , 2002. ...
Twenty-one dairy herds with a history of Neospora caninum-associated abortions were used for a longitudinal serological study. A total of 1,676 animals were blood sampled 3 times and used to evaluate a single serological screening for N. caninum antibodies. The results of the first serological screening were compared with the results based on three consecutive samples, whereby two or more positive or negative test results per animal were considered to determine its serological status as positive or negative, respectively. In both test regimes 95.3% of the animals had the same interpretation, of which 33.9% were seropositive, and 61.3% seronegative. Relative sensitivity of one-time sampling compared to three consecutive samplings was 94.7%, while relative specificity was 95.6%. Relative specificity differed between herds. Predictive values positive and negative of one-time sampling were 92.4 and 97%, respectively. The agreement between one-time sampling and three consecutive samplings, kappa, was 0.90. For evaluation of discrepant results age distribution and pedigree data were used to provide clues regarding likelihood of transmission. Age clustering of seropositive animals was interpreted to indicate a point source infection. Daughter-mother relationships were used for the interpretation of congenital infections. The proportion of congenital infection decreased with increasing parity of the mother. Seropositive heifers had 80% congenitally infected offspring, while in older cows 66% of the offspring was congenitally infected, possibly due an increased immunity to transplacental infection with age. It is concluded that a single serological screening of a whole herd in connection with an analysis of age distribution and pedigree data is a rapid and valid method to interpret the serologic status of individual animals and to study the mode of transmission of N. caninum.
... Post-natal bovine infection through oocysts shed by dogs (McAllister et al., 1998) or perhaps other, so far unidentified, definitive hosts appears to be likely (McAllister et al., 2000;Schares et al., 2002a). In herds with epidemic abortion, point source exposure to N. caninum, e.g. through oocyst-contaminated fodder or drinking water, is regarded as the most probable cause of infection (McAllister et al., 2000;Dijkstra et al., 2002;Schares et al., 2002a). ...
Tissue cysts of parasites of the genus Hammondia are rarely described in naturally or experimentally infected intermediate hosts. However, ultrastructural examinations on tissue cyst stages of Hammondia sp. are needed, e.g. to compare these stages with those of Neospora caninum and other related parasites. We describe a cell culture system employed to examine the in vitro development of tissue cysts of a Hammondia sp.-like parasite (isolate FOX 2000/1) which uses the European fox as a definitive host. Cells of a diploid finite cell line from embryonal bovine heart (KH-R; CCLV, RIE 090) were infected by inoculation of sporozoites und cultivated for up to 3 months. Transmission electron microscopic examination of 17 day old cell culture material revealed the presence of cyst walls. Infected cell cultures cultivated for 2 months were used to feed a fox. Six to 13 days post infection the fox shed large numbers (n=1.2 x 10(7)) of Hammondia-sp. like oocysts which could not be distinguished from those used to infect the cell culture as determined by DNA sequencing of the internal transcribed spacer 1 and the D2/D3 domain of the large subunit ribosomal DNA. To find out the proportion of parasitophorous vacuoles that had developed into tissue cysts, the expression of bradyzoite markers was examined by probing infected cell cultures with mouse polyclonal antibodies against Toxoplasma gondii bradyzoite antigen 1 (anti-BAG1) and rat monoclonal antibodies against a cyst wall protein (mAbCC2). Nineteen and 90 days post infection all parasitophorous vacuoles in the cell cultures were positive with anti-BAG1 and mAbCC2. This shows that biologically viable (i.e. infectious) tissue cysts of a fox-derived Hammondia sp. isolate (FOX 2000/1) can be efficiently produced in this cell culture system. Since in vitro cystogenesis of dog-derived Hammondia heydorni has not been observed yet, in vitro cyst formation might be one trait to separate fox-derived Hammondia sp. from H. heydorni on a species level.
... Post-natal bovine infection through oocysts shed by dogs (McAllister et al., 1998) or perhaps other, so far unidentified, definitive hosts appears to be likely (McAllister et al., 2000;Schares et al., 2002a). In herds with epidemic abortion, point source exposure to N. caninum, e.g. through oocyst-contaminated fodder or drinking water, is regarded as the most probable cause of infection (McAllister et al., 2000;Dijkstra et al., 2002;Schares et al., 2002a). ...
To obtain a rapid overview over the distribution of bovine Neospora caninum-infections in the German state of Rhineland-Palatinate, an ELISA to determine specific bovine antibodies against a p38 surface antigen of N. caninum tachyzoites was modified to examine bulk milk samples from cattle herds. Experimental bulk milk samples were used to demonstrate that the seroprevalence in a group of animals can be estimated with this ELISA. A cut-off was selected for the specific detection of herds having a seroprevalence > or =10%. About 90% of the dairy herds located in Rhineland-Palatinate were examined. An overall prevalence of bulk milk-positive herds of 7.9% (95% confidence interval 7.0-8.9%), respectively, was determined. Major regional differences in the distribution of bulk milk-positive herds were observed. Prevalences were higher in regions with an increased degree of urbanisation. Logistic regression was applied to model the prevalence of bulk milk-positive herds on a district and city level. Variables describing the dog density, mean temperature in July, mean temperature in January and the total yearly precipitation in districts and cities were able to explain most of the observed variability in the regional prevalences. Our results provide evidence that in addition to risk factors related to individual farms also risk factors related to the farm location such as dog density in the surrounding and climate factors are important in the epidemiology of bovine neosporosis.
... In both cases, a prerequisite would be the presence of a definitive host. As N. caninum infection in cattle is epidemiologically associated with the presence of a farm dog [14,31], the introduction of a dog to the farm recently before the abortion problems started is notable. That the dog was seronegative to N. caninum does not rule out that it had excreted oocysts and thereby deposited the infection in the environment of the cattle [20,25]. ...
A longitudinal study was performed in a Swedish dairy herd where Neospora caninum had been isolated from a stillborn calf. Starting in autumn 1994, blood samples from all female animals in the herd were collected once yearly until 1999. The sera were analysed for presence of IgG1 antibodies to N. caninum by the iscom ELISA, and by an avidity ELISA to establish the timing of infection. In addition, data on reproductive performance were compiled. During the study the percentage of seropositive female animals increased from 63% to 87%. In 1994 a large number of young animals tested seropositive although their dams were seronegative, indicating that a transmission of the parasite other than the vertical had recently occurred. Low avidity values supported this assumption. The annual abortion rate increased from a mean of 2% before the initiation of the study to 9% in 1994-1998. During the same time, as judged by the avidity data, a large proportion of the animals shifted from being recently to being chronically infected. The source of the external infection in the herd could not be identified.
... e factors are related with higher stocking density; an association of management and environmental factors (e.g. cow density) with seroprevalence was reported also by Sanderson et al. (2000); this could be explained by an increased probability of horizontal transmission in herds, likely due to a point-source exposure of cattle to infective oocysts. Dijkstra et al. (2002) examined eight dairy farms with evidence of post-natal transmission of neosporosis and the authors assumed that the source of infection was the feed contaminated by young dogs introduced on the farms 1.5 years before the first report of neosporosis in cattle. This hypothesis seems to be supported in our survey by the interaction between ...
A cross-sectional serological survey for Neospora caninum was carried out on beef and dairy cattle in southern and northern Italy. A total of 111 herds and 1140 animals were tested using an ELISA assay (CHEKIT-Neospora) to detect anti-N. caninum antibodies. Management and individual data were collected and analysed both by linear and logistic multiple-regression models in order to find good predictors of the cattle seroprevalence and anti-N. caninum antibody level. At least one seropositive animal was found in 49 herds (44.1%), of which 31 (39.7%) from southern Italy and 18 (54.5%) from northern Italy. A total of 126 head of cattle (11%) were found to be seropositive and the seroprevalence was lower in southern (8.7%) than in northern Italy (16%). One of the best predictors of neosporosis seroprevalence in this study was the practice of self-rearing replacement heifers. Further risk factors were linked to higher stocking density, i.e. animals farmed in large herds and with no summer or permanent grazing practices were more likely to be seropositive than others. Farms with two or more dogs had higher herd seropositivity than farms with one or no dogs and this factor interacted significantly with the farm size and presence of poultry. Among individual characteristics, seropositivity was higher in animals sampled in mid- or late-pregnancy compared to animals either in early pregnancy or not pregnant. There was a significant interaction between the factors for pregnancy status and grazing practices. None of the epidemiological data recorded was a good predictor of the anti-N. caninum antibody level.
Neospora caninum, Toxoplasma gondii, and Sarcocystis spp. are related Apicomplexan parasites that have 2 hosts in their life cycles. The definitive hosts excrete unsporulated (Neospora caninum, T gondii) or sporulated (Sarcocystis spp.) oocysts in their feces after ingesting tissue cysts from the tissues of ruminant intermediate hosts. These coccidians can cause abortion and neonatal mortality in ruminants. T gondii and Sarcocystis hominis (from cattle) are zoonotic. This article reviews information on the etiology, life cycle, diagnosis, control and prevention of these parasites and the diseases they cause in ruminants.
Acute primary or persistent infection of cattle with Neospora caninum can induce abortion. The abortions are triggered by lesions caused by the protozoon during its obligatory intracellular multiplication in foetal tissues and in the maternal part of the placenta. In addition, the infection may be able to favour abortions indirectly via changes of the immunological equilibrium within the foeto-placental unit, i.e. via an increased production of pro-inflammatory cytokines. In most cases, transplacental transmission of the infection does not cause abortion but leads to the birth of persistently infected, healthy calves. It is assumed that the majority of N. caninum-positive cattle in Germany become prenatally infected via their mother. This vertical route of transmission is very efficient and allows N. caninum to survive for several generations once a breeding line has become infected. Contamination of the forage with N. caninum oocysts shed by definitive hosts is regarded the most important source of infection which is able to introduce N. caninum horizontally into a herd or to spread the infection from one breeding line to another. The dog is the only known definitive host in Europe that can shed N. caninum-oocysts with the faeces. Risk factor studies suggest that dogs kept on cattle farms play a predominant role in spreading the infection horizontally. Other dogs shed N. caninum oocysts only very rarely; consequently they are regarded as less important for the transmission of the infection. A diagnosis is reached by the direct or indirect demonstration of the infectious agent in foetal tissues. Histological lesions, like multifocal non-suppurative encephalitis are regarded as characteristic. A seroepidemiological examination of pregnant cattle in the herd may confirm the diagnosis. Since the infection cannot be treated by chemotherapy and as there is no vaccine licensed in Germany, it is of utmost importance to adhere to hygienic measures to reduce the chance for a horizontal transmission of the infection. Vertical transmission can be prevented by excluding seropositive animals from breeding. These measures are only reasonable in herds where abortions are more likely to occur in the infected cattle breeding lines than in the non-infected ones.
Recent work has highlighted and enumerated the economic annual losses due to Neospora caninum abortions worldwide, which should provide strong motivation for the control of bovine neosporosis. However, with the recent withdrawal from sale of the only commercially available vaccine, control options for N. caninum have become more restricted. While researchers continue to work on developing alternative efficacious vaccines, what are the control options presently available for the cattle industries? At the practical level, recommendations for 'Test-and-cull', or 'not breeding from seropositive dams' stand diametrically opposed to alternative options put forward that suggest a primary producer is better advised to keep those cows in the herd that are already seropositive, i.e. assumed to be chronically infected, and indeed those that have already aborted once. Treatment with a coccidiostat has been recommended as the only economically viable option, yet no such treatment has gained official, regulatory approval. Dogs are central to the life cycle of N. caninum and have repeatedly been associated with infection and abortions in cattle by epidemiological studies. Knowledge and understanding of that pivotal role should be able to be put to use in control programmes. The present review canvasses the relevant literature for evidence for control options for N. caninum (some of them proven, many not) and assesses them in the light of the authors' knowledge and experience with control of N. caninum.
Le parasite N. caninum est un protozoaires identifié il y a une vingtaine d'années.Bien que l'infec-tion par Neospora caninum puisse se manifester par des symptômes neurologiques en pathologie bovine néonatale, sa principale répercussion économique et sanitaire en élevage est due aux avortements. Son cycle parasitaire est encore imparfaitement connu. Ses hôtes définitifs actuellement identifiés avec certitude sont le chien, le coyote et le dingo, mais le renard est aussi fortement suspecté. Une bonne connaissance du cycle évolutif du parasite et de la physiopathologie de la néosporose est indispensable pour définir des méthodes de lutte efficaces. À ce jour, il n'existe pas de traitement. De nom-breux essais vaccinaux sont réalisés avec différentes stratégies. Seules des méthodes de lutte sanitaire sont envisageables avec un rôle essentiel de conseil pour le vétérinaire sanitaire. Neospora caninum is an apicomplexan parasite, identified about twenty years ago. Although it can cause neurological symptoms in newborn cattle, its main economic and health repercussion in breeding is due to abortions. The life cycle of N. caninum is not yet fully understood. Its currently identified final hosts are dogs and coyotes, but foxes are also strongly suspected. To be effective, treatment and prophylaxis must be based on sound knowledge of the life cycle and pathophysiology of this pro-tozoosis. There is no treatment currently available. Many vaccine studies are being performed using various strategies, but only disease control methods are possible for the moment, alongside the crucial advisory role of veterinary practitioners.
Neospora caninum is an apicomplexan parasite, identified about twenty years ago. Although it can cause neurological symptoms in newborn cattle, its main economic and health repercussion in breeding is due to abortions. The life cycle of N. caninum is not yet fully understood. Its currently identified final hosts are dogs and coyotes, but foxes are also strongly suspected. To be effective, treatment and prophylaxis must be based on sound knowledge of the life cycle and pathophysiology of this protozoosis. There is no treatment currently available. Many vaccine studies are being performed using various strategies, but only disease control methods are possible for the moment, alongside the crucial advisory role of veterinary practitioners.
Neospora caninum is an Apicomplexan heteroxenous parasite with dog as domestic definitive host and bovine as intermediate host. This parasite is responsible for many abortions in bovine worldwide. It is an obligate intracellular parasite which is invasive since it can reach deep host organs such as brain, lungs, liver or spleen. The host immune response against this pathogen was essentially studied in mouse and bovine. This article presents the most relevant studies performed on these models and the vaccine trials tested. It appears that although the humoral specific immune response (specific antibodies) is intense with seropositive hosts, the cellular immune response mediated mainly by gamma interferon (IFN-γ) is the key of the control to infection by N. caninum. This cytokine is produced by Th1 lymphocytes and inhibits the Th2 response. If the protection is efficient in non-pregnant animals remaining mostly asymptomatic, the situation is more critical in pregnant animals. Indeed, in this case Th1 response is reduced by Th2 response to guaranty the maintain of the fetus. It can conduct to a vertical transmission of N. caninum leading in many cases to abortion. The fetal immune system is efficient after 4 months of pregnancy and can act against the parasite leading to viable but seropositive calves. Vaccination can be modelised in mouse and lead to the development of a commercially available vaccine in bovine allowing a reduction of clinical signs and abortions in host but not systematically. The understandding of the host-parasite interaction should allow to more accurately act in a prophylactic way to this pathogen.
SUMMARY Recent work has highlighted and enumerated the economic annual losses due to Neospora caninum abortions worldwide, which should provide strong motivation for the control of bovine neosporosis. However, with the recent withdrawal from sale of the only commercially available vaccine, control options for N. caninum have become more restricted. While researchers continue to work on developing alternative efficacious vaccines, what are the control options presently available for the cattle industries? At the practical level, recommendations for 'Test-and-cull', or 'not breeding from seropositive dams' stand diametrically opposed to alternative options put forward that suggest a primary producer is better advised to keep those cows in the herd that are already seropositive, i.e. assumed to be chronically infected, and indeed those that have already aborted once. Treatment with a coccidiostat has been recommended as the only economically viable option, yet no such treatment has gained official, regulatory approval. Dogs are central to the life cycle of N. caninum and have repeatedly been associated with infection and abortions in cattle by epidemiological studies. Knowledge and understanding of that pivotal role should be able to be put to use in control programmes. The present review canvasses the relevant literature for evidence for control options for N. caninum (some of them proven, many not) and assesses them in the light of the authors' knowledge and experience with control of N. caninum.
The infection by Neospora caninum of different cattle breeds in dairy properties in two municipalities of the South Fluminense Paraíba Valley, state of Rio de Janeiro, was evaluated. Considering a sampling universe of 2,491 cows, blood samples were collected from 563 dairy cows in 57 farms, which were randomically selected in proportion to the number of animals, using a random stratified sampling system. For each property the number of selected cows was proportional to the herd size. Abortion or other reproductive disorders were not considered as criteria for selecting the animals, and seropositivity was determined by indirect enzyme-linked immunosorbent assay (ELISA). A high association (p=0.006) between seropositivity and racial patterns was found. The analysis revealed that in comparison of pure black-and-white Holstein cows versus Zebu (p=0.0028), Holstein cows showed 2.65 times greater odds for seropositivity. In the same way, by comparing black-and-white Holstein versus Zebu + crossbreed Zebu/Holstein (p=0.01), it was noted that there is 2.23 times more chance for seropositivity in Holstein cattle. There were no significant differences concerning the comparison of Holstein cattle versus crossbreed Zebu/Holstein (p=0.08) or Zebu versus crossbreed Zebu/Holstein (p=0.11). This study supports the hypothesis that there is a close association between cattle breeds and the frequency of infection by N. caninum.
Neospora caninum es un parásito apicomplexa que ha sido identificado como una de las principales causas de aborto en ganado bovino y responsable de patologías neurológicas en diversas especies animales. Esta íntimamente relacionado con Toxoplasma gondii, con el que comparte la habilidad para persistir dentro del hospedador por tiempo indefinido en estado latente, formando quistes tisulares que contienen en su interior parásitos con una capacidad de multiplicación reducida, denominados bradizoítos. Se compararon diferentes tratamientos a fin de inducir la conversión a bradizoíto in vitro. El tratamiento con nitroprusiato sódico 70 M durante 7 días consiguió la mejor tasa de transformación y el mejor rendimiento de vacuolas parasitóforas observadas. Además se identificaron y clonaron los genes NcSAG4 y NcBSR4 de Toxoplasma gondii, que se expresan específicamente durante el estadio de bradizoíto. Los análisis llevados a cabo sugieren que tanto NcSAG4 como NcBSR4 tendrían una regulación durante la transcripción y serían expresados de manera específica durante el estadio de bradizoíto de forma temprana o tardía, respectivamente.
The protozoan parasite Neospora caninum and bovine viral diarrhoea virus (BVDV) are major causes of abortion in cattle and related with economic losses in many countries. When introduced into a herd, both infections can be expected to remain for a long time if no control measures are taken. The purpose of this study was to investigate the prevalences of N. caninum and BVDV infections in dairy cows in South Vietnam. Specific goals were to study the seroprevalences of the infections in dairy cows from state herds and smallholder farms, and if there were differences in seroprevalences between imported Holstein Friesian cows and local crossbreeds.
A total of 345 serum samples, including 215 sera collected from 5 state farms and 130 sera from 97 smallholder herds, from southern Vietnam were analysed for presence of antibodies to N. caninum and BVDV. In state herds with imported cows, the N. caninum and BVDV seroprevalences varied between 38-53% and 78- 93%, respectively. The infection rates were higher in imported cows than in local crossbreeds. The results suggested that horizontal transmission of N. caninum was occurring in at least 4 of the 5 herds. Among cows from smallholder herds with only local crossbreeds, the prevalences of N. caninum and BVDV were 19% and 18%, respectively. BVDV antigen was not found in any cow. This is the first report on BVDV infection in Vietnam.
It was concluded that N. caninum and BVDV infections are present and appear to be widespread in dairy cows in south Vietnam. Given the high prevalence among imported cows found in this study, it seems advisable that only cattle that are pretested free from N. caninum infection are imported into the country. Further, it is important not to import any persistently infected BVDV cattle or antibody positive cows that may carry infected foetuses.
Feces from 15 dogs at 2 different foxhound kennels in the U.K. were examined microscopically for the presence of oocysts of Neospora caninum. One sample containing approximately 400 candidate oocysts per gram was positive in a polymerase chain reaction (PCR) using N. caninum-specific primers. In a sample taken 4 mo later from the same hound. N. caninum oocysts were again detected visually and by PCR. This is the third reported case of a dog naturally excreting oocysts of N. caninum and suggests that oocyst excretion can occur over a relatively long period of time in some circumstances or that reshedding may occur.
Phalloidin-fluorescein isothiocyanate staining of filamentous actin was used to identify muscle systems within the cercariae of Schistosoma mansoni. Examination of labeled cercariae by confocal scanning laser microscopy revealed distinct organizational levels of myofiber arrangements within the body wall, anterior cone, acetabulum, and esophagus. The body wall throughout showed a typical latticelike arrangement of outer circular and inner longitudinal myofibers, with an additional innermost layer of diagonal fibers in the anterior portion of the body. Circular and longitudinal fibers were also evident in the anterior organ and esophagus and, to some extent, the ventral acetabulum. Most striking was the striation of the cercarial tail musculature.
There are many parasites that affect the ruminant central nervous system. Clinical signs can vary dramatically based on the location and mobility of the parasite. Clinical disease can occur due to the physical presence of the parasite and the resulting host immune response or the toxin produced by the parasite. Differentiating the cause of disease is particularly important because prognosis,treatment, and subsequent control measures vary dramatically depending on the disease process. This article focuses on the pathogenesis,treatment, and control of some of the more common parasitic diseases of the ruminant central nervous system.
Studies were conducted to determine the pathogenic potential of the recently isolated bovine Neospora protozoa (BPA-1) for the bovine fetus. Cows chosen for study had Neospora titers < 160 using an indirect immunofluorescent antibody (IFA) test. Four experimental groups were studied. In group 1, 2 fetuses were inoculated in utero at 118 days gestation with culture-derived Neospora tachyzoites. A pregnant control cow was housed in the same pen, observed daily and screened serologically for evidence of exposure to Neospora. In group 2, 2 cows were infected with Neospora tachyzoites at 138 or 161 days gestation, and 1 control cow was given uninfected cell culture suspension simultaneously at 154 days gestation. Groups 3 (85 days gestation) and 4 (120 days gestation) each consisted of 2 cows infected with Neospora tachyzoites and 1 control cow given uninfected material at the same stage of gestation. Dead fetuses were surgically removed from the infected cows in group 1 on postinfection day (PID) 17. The histopathology was compatible with protozoal fetal infection, and protozoa were identified by immunohistochemistry. Viable fetuses were removed surgically from cows in group 2 on PID 28-30. The histopathology was compatible with protozoal fetal infection, protozoa were identified by immunoperoxidase techniques, and Neospora tachyzoites were reisolated in vitro from tissues of the 2 infected fetuses. In groups 3 and 4, the control fetus and 1 infected fetus were removed surgically between PID 26 and PID 33. The remaining infected cows were observed until fetal death or abortion occurred.(ABSTRACT TRUNCATED AT 250 WORDS)
A prospective cohort study was undertaken on two central California dairies, A and B, to estimate prevalence of congenital infection with Neospora caninum, to characterize temporal variation in prevalence, to determine if occurrence of congenital infection was associated with specific dam and calf attributes, and to estimate the effect of congenital infection on calfhood mortality. Of the 405 calves enrolled over a period of 2 1/2 y on dairy A and dairy B, 30.6% (85/278) and 53.5% (68/127), respectively, were seropositive precolostrally to N. caninum, as determined by an ELISA test. Adult cow seroprevalence at calving was 36.0% (82/228) for dairy A, and 57.9% (33/57) for dairy B. No evidence was found for a significant increasing or decreasing trend in adult and precolostral seroprevalence through the study period (P > or = 0.26). For both herds combined, 81% of seropositive cows (93/115) and 5% of seronegative cows (8/170) had congenitally infected calves. Seroprevalence did not increase with cow age on either dairy (P > or = 0.47). The probability of a calf being congenitally infected was not associated with dam age, dam lactation number, dam history of abortion, calf gender, or length of gestation (P > or = 0.11). High dam ELISA values at calving were significantly associated (P < or = 0.001) with an increased probability of congenital infection in her calf. Results of survival analyses of female calves available for follow-up indicated a consistently greater survivorship to 90 d in congenitally infected calves than in noninfected calves on both dairies, which was significant for dairy A (P = 0.07, n = 186) but not for dairy B (P = 0.69, n = 72), thus indicating that congenital infection does not necessarily have a detrimental effect on calf health. The findings of a similar magnitude in congenital infection rate and adult cow prevalence, the lack of increasing seroprevalence with cow age, the lack of an effect of dam age on precolostral seropositivity, and the constant seroprevalences during the study period, suggest that, in the two dairies studied, congenital transmission constituted a substantial amount of infection and was likely the major mode of transmission of N. caninum.
Aborting and nonaborting cows and their dams or daughters were studied to determine if herd abortion problems were associated with the presence of Neospora caninum antibodies and to estimate when aborting cows may have acquired the infection. Cows were sampled from 20 herds that had experienced an abortion epidemic presumed to have been caused by N. caninum and from 2 herds experiencing endemic abortion. Seroprevalence for 14 herds experiencing an epidemic ranged from 7% to 70%, as estimated by enzyme-linked immunosorbent assay. A strong association between seropositivity and abortion was found for only 5 of 14 herds with a presumed diagnosis of N. caninum abortion (P < or = 0.015, lower 95% confidence interval of odds ratio > or = 1.2), indicating N. caninum may be overdiagnosed as the cause of an abortion epidemic in some herds. No association was found between dam and daughter seropositivity for herds experiencing an epidemic (P > or = 0.17), suggesting that most cows aborting during an epidemic were infected postnatally. For the 2 herds with endemic abortion (A, B), odds of an aborting cow having N. caninum antibodies were 3.4-fold (herd A) and 7.0-fold (herd B) higher than odds for nonaborting cows (P < or = 0.05). Cows that aborted a fetus infected with N. caninum were more likely to have had a previous seropositive daughter than were nonaborting seronegative cows (P < or = 0.0025), suggesting that infection had been acquired before conception of the aborted fetus.
Prevalence of antibody to Neospora caninum (NC) in Japanese dogs were examined. The antibody was positive in 15 of 48 dogs (31.3%) reared in the dairy farms that had case of the abortions due to NC infection or had the cattle seropositive to NC, whereas the prevalence was 7.1% (14 of 198 dogs) among the dogs kept in urban areas. In one dog breeder, all 17 Shetland sheepdogs older than 7 months were seropositive, and one pup was diagnosed as neosporosis 2 months before the first serological examination. The antibody titers of the dogs kept at this breeder were almost unchanged for 1.5 years. Serological evidence of the dogs in the dairy farms and urban areas indicates the transmission of NC between dogs and cattle. Also serological results of the dogs in one breeder may suggest the potential horizontal transmission among dogs.
The performance of three enzyme-linked immunosorbent assays (ELISA) for detection of antibodies to Neospora caninum in bovine sera was evaluated by using various categories of sera. Two commercial ELISA methods, one based on chemically fixed intact tachyzoites and one based on a sonicate lysate of whole tachyzoites, were compared with an in-house ELISA based on a detergent lysate of whole tachyzoites. A brief description of the development of the latter ELISA is also given. There was good agreement among all three tests with regard to postabortion sera. By using acute-phase abortion sera from cows with confirmed N. caninum-induced and non-N. caninum-induced abortions, satisfactory levels of sensitivity and specificity were calculated for all tests. In addition, similar test results were obtained with postpartum samples from dams and calves. However, considerable differences were found between test results of sequential samples and cross-sectional and total-herd samples. Apparently, these discrepancies were due to different sensitivities of the tests for detection of low antibody levels in chronically infected animals. It is suggested that these differences were primarily due to the use of different antigens and different test sample dilutions. It is concluded that all tests are applicable as an additional diagnostic tool in cases of abortion in cattle and for monitoring of congenitally infected calves. For herd screening, the lysate-based ELISAs appear to be more adequate because of their higher sensitivities.
Dogs were investigated to determine if they are definitive hosts of Neospora caninum. Four dogs were fed N. caninum tissue cysts in infected mouse tissue, and two negative control dogs were fed uninfected mouse tissue. Dog faeces were examined daily for 30 days using a sucrose flotation technique. Three challenged dogs shed spherical to subspherical unsporulated oocysts, measuring 10 to 11 microns in diameter. Oocysts sporulated within 3 days and contained two sporocysts, each with four sporozoites. Outbred, inbred, and gamma-interferon knockout mice were inoculated with canine faecal extracts and monitored for evidence of neosporosis using a variety of morphologic, immunohistologic, serologic, and genetic analyses. Mice that received faeces from each dog observed to shed oocysts were demonstrated to have neosporosis by two or more techniques. One mouse was demonstrated to be infected with N. caninum by immunohistochemistry, ultrastructural analysis, and a species-specific PCR test. No evidence of neosporosis was observed in control animals. Based on this study, dogs are a definitive host of Neospora caninum.
All the cattle in 14 dairy herds in England were tested for Neospora caninum-specific antibodies with a commercial ELISA. Three of the herds had had sporadic abortions, eight had had endemic abortions and three had had epidemic abortions associated with N caninum before the study. Of 4295 cattle tested, 17.1 per cent were seropositive and the herd-specific prevalence ranged from 7.3 per cent to 44.8 per cent. No significant effect of either herd size (P = 0.988), endemic (P = 0.869) or epidemic (P = 0.138) patterns of abortion on herd-specific prevalence was found by using logistic regression analysis. There was no evidence in any herd of a significant increase in prevalence with age; the prevalence in seven-to 12-month-old cattle was not significantly different (P > 0.400) from the prevalence in older cattle, except that there was a significantly lower prevalence (P = 0.017) in 13-to 24-month-old cattle. The results of this study are consistent with vertical transmission being the major route of N caninum transmission in these herds.
The seroprevalence of Neospora caninum infection was estimated from a sample of 889 cattle from 43 dairy herds in three counties in the Asturias region of Spain. The true prevalence of infection was estimated to be 30.6 per cent (95 per cent confidence interval (CI) 27.6 to 33.6). Seropositivity was associated with abortion during the previous year (odds ratio (OR)=3.31, P<0.001) and was slightly higher among purchased cattle (37.6 per cent), than among cattle raised on the farm (29.1 per cent) (P=0.078). Seropositive cows were more likely than seronegative cows to have had a seropositive dam (OR=2.3, P=0.011), suggesting that congenital transmission contributed to about 56 per cent of the infections. Herds with a true seroprevalence above 10 per cent had more dogs on the farm, than herds with a lower prevalence (P=0.032). The ORS relating abortion to seropositivity in individual herds ranged from 0.7 to 19, indicating that some herds experienced few abortions caused by N. caninum, while others experienced more abortions due to the organism. Overall, 38.7 per cent of the abortions were estimated to have been attributable to N. caninum.
To determine whether cows with evidence of previous infection with Neospora caninum were less likely to abort or give birth prematurely during an outbreak of neosporosis, compared with herdmates with evidence of primary infection.
Cohort study.
208 pregnant beef cows.
Aborted fetuses and calves born prematurely were examined during an outbreak of neosporosis in a herd of beef cows. Sera were collected from all cows during the outbreak and again 71 days later. Cows were classified into groups on the basis of normal and abnormal reproductive outcomes. Sera were examined, using an avidity ELISA procedure for N caninum, and results were compared between groups and among time points.
Antibody concentrations decreased significantly and IgG avidity values increased significantly over time. During the outbreak, cows with normal reproductive outcomes were significantly more likely to have high IgG avidity values than cows with abnormal reproductive outcomes.
The herd had numerous abortions and premature births with evidence of recent point-source exposure to N caninum. Therefore, to reduce risk of transmission of N caninum to cattle, attempts should be made to prevent canine feces from contaminating feed, especially feedstuffs used to prepare mixed rations for cattle. Cows with evidence of previous exposure to N caninum were less likely to abort or give birth prematurely during the outbreak than cows with primary infections with N caninum; this finding suggests development of protective immunity in previously infected cows.
A longitudinal study was performed in a Swedish dairy herd where Neospora caninum had been isolated from a stillborn calf. Starting in autumn 1994, blood samples from all female animals in the herd were collected once yearly until 1999. The sera were analysed for presence of IgG1 antibodies to N. caninum by the iscom ELISA, and by an avidity ELISA to establish the timing of infection. In addition, data on reproductive performance were compiled. During the study the percentage of seropositive female animals increased from 63% to 87%. In 1994 a large number of young animals tested seropositive although their dams were seronegative, indicating that a transmission of the parasite other than the vertical had recently occurred. Low avidity values supported this assumption. The annual abortion rate increased from a mean of 2% before the initiation of the study to 9% in 1994-1998. During the same time, as judged by the avidity data, a large proportion of the animals shifted from being recently to being chronically infected. The source of the external infection in the herd could not be identified.
The performance of the Dutch cattle I&R system was analysed, with emphasis on the potential use of the system for the control of an outbreak of foot and mouth disease (FMD). The analysis showed that not all mutations were centrally registered within the three working days that are allowed to pass between the actual change and the obligatory report. In particular, young calves and cattle heading for slaughter were reported too late. During an outbreak of FMD, the best strategy to trace animals off a farm seems to be first to identify all animals on the farm, using a preprocessed list of the animals that should be present on the farm according to the I&R system. Then all the animals that have left the farm during the last month can be traced in the central I&R computer or by asking the person to whom the farmer sold the cattle (the next owner). In the present study, 54% of the animals were localized within one day, and 94% within one week. Finally, some suggestions for improvement of the system are given.
Transmission parameters of Neospora caninum infections in dairy cattle were determined in six herds with a history of Neospora-associated abortions, using an antibody-detection ELISA to detect evidence of infection. A total of 124 seropositive dams and their calves were tested at calving to estimate vertical transmission, and 154 seronegative heifers were monitored prospectively from birth for evidence of post-natal infection. The probability of vertical transmission was very high; 95.2% (95% confidence interval: 89.8%, 98.2%) of the seropositive dams produced calves that were seropositive prior to consumption of colostrum. In the prospective study, three heifers seroconverted, by 1, 8 and 16 months of age, and the overall incidence rate of seroconversion was 1.9 per 100 heifer-years at risk, ranging from 0 to 4.1 per 100 heifer-years at risk within herds. If heifers with inconclusive ELISA results were included in the analysis, the incidence rate of seroconversion was 3.8 per 100 heifer-years at risk, ranging from 0 to 8.3 per 100 heifer-years at risk within herds. This study showed that vertical transmission was the major route involved in the spread of N. caninum in these herds, and that there was only a low detectable level of horizontal transmission. However, further studies are needed to provide parasitological evidence of infection in those heifers that seroconverted.
Dogs from dairy farms with a known prevalence of Neospora caninum antibodies in the cattle were examined for the presence of N. caninum antibodies using an ELISA. Data of farm dogs were compared with those of dogs examined at a university clinic, which originated mainly in urban areas. Of the 152 farm dogs, 36 (23.6%) were seropositive to N. caninum, which was significantly higher than the proportion of seropositives in the clinic dog population (19 of 344, 5.5%). Seroprevalence was significantly higher (P = 0.01) in female dogs than in male dogs. Seroprevalence in dogs increased with age, indicating postnatal infection. Seropositivity to N. caninum in farm dogs was strongly correlated with a high prevalence of N. caninum antibodies in the cattle. At farms where no dogs were present, the seroprevalence to N. caninum in the cattle was significantly lower (P = 0.0002) than in farms where dogs were present. These findings suggest that there is a relationship between N. caninum infection of farm dogs and cattle. Since dogs have been shown to be definitive hosts of N. caninum, cattle may be infected by exposure to canine oocysts. Further research is needed to find out whether and how dogs may acquire the infection from cattle.
Neospora caninum has been identified as a major cause of abortion in cattle in a number of countries throughout the world. Until the recent demonstration that dogs can serve as a definitive host of this parasite, it was not possible to study the infection in cattle orally exposed to oocysts. The aim of this study was to investigate the potential of N. caninum oocysts to infect calves, and to define initial immune responses that arise after oral infection. Seven calves were fed approximately 10(4)-10(5) N. caninum oocysts, three calves served as uninfected controls. Before infection, all calves were serologically negative for anti-Neospora antibodies and the calves were non-reactive to Neospora antigen in an in vitro lymphocyte proliferation assay. Peripheral blood lymphocytes from inoculated calves were able to mount in vitro proliferative responses to crude N. caninum antigen extract as early as 1 week p.i. Within 2 and 4 weeks p.i., Neospora-specific IgG1 and IgG2 antibodies were detected by IFAT and ELISA in serum from infected calves but not from sham-infected calves. The continued presence of reactive cells in the blood, spleen and mesenteric, inguinal, bronchial lymph nodes was seen as late as 2.5 months p.i., and parasite DNA was detected in the brain and spinal cord of the infected animals by PCR, indicating that the cattle were infected by oral inoculation of N. caninum oocysts collected from dogs, and that the animals were systematically sensitised by parasite antigen.
The performance of the Dutch cattle I&R system was analysed, with emphasis on the potential use of the system for the control of an outbreak of foot and mouth disease (FMD). The analysis showed that not all mutations were centrally registered within the three working days that are allowed to pass between the actual change and the obligatory report. In particular, young calves and cattle heading for slaughter were reported too late. During an outbreak of FMD, the best strategy to trace animals off a farm seems to be first to identify all animals on the farm, using a preprocessed list of the animals that should be present on the farm according to the I&R system. Then all the animals that have left the farm during the last month can be traced in the central I&R computer or by asking the person to whom the farmer sold the cattle (the next owner). In the present study, 54% of the animals were localized within one day, and 94% within one week. Finally, some suggestions for improvement for the system are given.
A cohort study was undertaken on a dairy experiencing endemic Neospora caninum abortions, to characterize dam serologic variations during pregnancy, and to determine if dam N. caninum antibody levels during gestation predicted congenital infection or abortion. Blood samples were collected monthly during pregnancies of 254 cows and precolostrally from 87 of their calves. Antibody levels, as measured by an enzyme-linked immunosorbent assay, indicated 60.6% of cows were seropositive at some time during pregnancy and 87.4% of seropositive cows were seropositive throughout pregnancy. The rate of seroconversion was 8.5/100 cows/yr. The risk of abortion for seropositive cows at the time of pregnancy diagnosis and during gestation was twice that for seronegative cows (P = 0.025, P = 0.006). Calves born to seropositive cows were more likely to be seropositive at birth if the dam had high antibody levels at 240 days of gestation (P = 0.04) and an increase in antibody levels between 90 and 240 days (P = 0.08) than if the respective values of the dam were low or decreasing. Seropositive cows with high antibody levels at 180 and 210 days of gestation were less likely to abort than cows with low antibody levels at those times (P = 0.05, P = 0.03). Results support a causal effect between exposure to N. caninum and abortion, indicate that acquisition of infection during pregnancy is not necessary for congenital infection or abortion to occur, and suggest that maternal immune response influences congenitial infection and abortion.
To identify risk factors associated with Neospora caninum infection in dairy herds in Québec and to estimate seroprevalence in case and control herds.
Herd-based case-control and seroprevalence study.
3,059 cows from 24 case and 22 control dairy herds in Québec.
Blood samples were obtained from each cow, and sera were tested, using an ELISA, for antibodies to N caninum. Owners of herds answered questionnaires requesting information on demographics and herd management practices. Seroprevalence was compared between case and control herds, using the Mann-Whitney test. Risk factors were compared between case and control herds, using logistic regression.
All case herds and 73% of control herds had at least one seropositive cow. Median seroprevalence was significantly greater among case herds (22.5%) than among control herds (7.5%). Dogs were found most often and in greatest numbers on farms housing case herds compared with control herds during the past 3 years.
Although the exact role that dogs have in transmission of N caninum in dairy herds needs to be elucidated, dogs should have limited access to barns and cattle.
The association of Neospora caninum infections with cattle families was examined in a dairy cattle herd with sporadic abortions using three different serological tests. Cattle seropositive for N. caninum clustered in six families, three of which encountered abortions. In absence of age-related differences in the N. caninum seroprevalence, the family association of N. caninum infection indicated that congenital infection represented the predominant route of transmission in this herd. Fourteen (93%) out of 15 descendants of 10 seropositive cows were seropositive themselves. Only one female calf of a seropositive cow remained seronegative and gave birth to a calf which was tested seronegative again. Only one seronegative cow that had two seronegative descendants also gave birth to one seropositive calf. This was the only indication for potential postnatal transmission that occurred in the herd. The results of this study suggest that the N. caninum-infection can be maintained over several generations at a nearly constant prevalence level, apparently without a need for dispersion by an definitive host.
Two mixed-breed littermate dogs were fed mouse brains containing tissue cysts of the NC-beef isolate of Neospora caninum. Both dogs excreted N. caninum oocysts in their feces. Dog 1 which was given methylprednisolone acetate (MPA) prior to ingesting tissue cysts, excreted oocysts on days 5 to 10 inclusive and on day 17 after ingesting tissue cysts. Dog 1 had a serum antibody titer of 1:200 in the indirect fluorescent antibody test (IFAT) 35 days after it was fed tissue cysts. Dog 2, which was not treated with MPA, excreted oocysts on Day 6 and Day 9 after ingesting tissue cysts. Antibodies to N. caninum were not found in a 1:25 dilution of serum on any examination period for Dog 2 during the study. Neospora caninum was not found in the tissues of either dog by histological or immunohistochemical means following necropsy 42 days after being fed tissue cysts. The identity of the oocysts excreted in the feces of the dogs was confirmed by mouse inoculation studies.
Neospora caninum has emerged as a major cause of abortion in cattle in many countries. This paper reviews recent advances in the life cycle and biology of Neospora with the emphasis on bovine neosporosis. The role of the recently discovered oocyst stage of N. caninum in the epidemiology of neosporosis is discussed. Progress made in serologic diagnosis of N. caninum infection is discussed. There is no vaccine for preventing Neospora-induced abortions in cattle or to prevent oocyst shedding in dogs.
An epidemiological study was conducted in Orne (France) on randomly selected dairy herds (42 herds including 1,924 cows and heifers, which were at least 15 months old). The aim was primarily to estimate the seroprevalence of Neospora caninum infection from two blood samples per cow, using an enzyme-linked immunosorbent assay (ELISA) for N. caninum (one positive result indicating infection). The second aim was to test the association between some individual and herd factors and N. caninum seropositivity with a logistic model including a random term effect. The prevalence was estimated at 5.6% (107 seropositive animals). At least 27 of the 42 herds had one seropositive cow or heifer. The intra-herd seroprevalence varied from 1.1 to 8% for 18 positive herds (66.7%). Dogs were present in 36 farms and 104 of the 107 seropositive animals were exposed to them. The factors associated with individual seropositivity were the presence of cats (OR = 0.17; P < 0.001), dogs (OR = 4.35; P = 0.02), rabbits and/or ducks (OR = 2.10; P = 0.04), long calving periods (12 months) (OR = 0.44; P = 0.007), tethered housing (OR = 2.50; P = 0.01), somatic cell counts (200-400 x 10(3) cells/mL) (OR = 0.24; P < 0.001) and pond water supply (OR = 2.43; P = 0.04). In conclusion, the animal and intra-herd seroprevalences were low in dairy cows from Normandy, France.
Abortion outbreaks caused by infection with Neospora caninum in beef cattle have not been well documented. Neospora caninum infection was confirmed in 4 fetuses that were aborted by cattle in a 350-head beef herd; an additional 58 cattle aborted during the next 2.5 months. Overall, 44.4% (157/354) of the cattle in the herd did not become pregnant or experienced fetal loss during this period. Initially, 81.3% (282/347) of the herd was seropositive for antibodies to N caninum, and seropositive cows were 6.2 times as likely to not be pregnant as were seronegative cows. Other potential causes of abortion were not identified in this herd. Following the outbreak, few cattle in the herd or in a second exposed herd seroconverted, but high antibody titers persisted in most seropositive cattle through the end of the calving season. Evidence of cow-to-fetus transmission of the organism was detected in > 82% of seropositive cows.
A study was done of the descendants of cows from 4 dairy herds in which there had been N. caninum abortion outbreaks. Precolostral antibodies to N. caninum were demonstrated in 34 of 50 (68%) F1 calves and in 14 of 17 (82%) F2 calves from cows that aborted during the outbreaks. In 214 F1 progeny, N. caninum seroprevalence was nearly 50%, and there was a significant association between serostatus of the offspring and serostatus of dams. These observations indicated that congenital infection was an important mode of transmission after abortion outbreaks in these herds. A total of 52 abortions was recorded in 293 pregnancies of F1 progeny cows (1 to 3 pregnancies per animal). It was found that seropositive F1 cows had a three-fold increased abortion risk compared with seronegative F1 cows. In 2 of 10 abortions in seronegative cows evidence for N. caninum infection was found, suggesting that a low level of postnatal infection may also have occurred. It is concluded that N. caninum-infected calves should not be used as replacement stock, to decrease the future risk of abortion in dairy herds.
A 2 to 1 matched case control study design was used to analyze herd level risk factors for Neospora caninum-associated abortion storms in 47 dairy herds. Data were obtained using a questionnaire regarding the state of affairs at the farms over the 2 years prior to the abortion storm. The questionnaire included 120 variables considered to be potential risk factors for either introduction of infection or recrudescence of chronic infection. The relationship between risk factors and case control pairs was analyzed by conditional logistic regression using a three-steps procedure. In addition, cross sectional serology was used to assess the possible role of concomitant infections. The main factors that were significant in the analysis and that were considered to have potential biological relevance were the presence of dogs, the presence of poultry, and the feeding of moldy maize-silage during summer. For both the presence of dogs and the presence of poultry on the farms, a linear relationship was found between the number of animals and the assessed risk for an abortion storm. These findings suggest a possible role of these species in the transmission of N. caninum. Further evidence for such a role of dogs was the significant association between the presence of dogs and the presence of seropositive cattle in the control herds. The feeding of moldy fodder is considered to be a factor which may induce recrudescence of a latent N. caninum-infection by mycotoxins causing immune suppression. We also found some evidence for a possible influence of management practices around calving and a high prevalence of retained afterbirths. No significant association was found for herd level prevalence of antibodies to bovine viral diarrhea virus, bovine herpesvirus 1, Leptospira hardjo or Salmonella dublin.
Abortion storms in 50 dairy herds in The Netherlands were reported in which there was a strong association with Neospora caninum-infection. The duration of the abortion storms ranged from 6 to 65 d (mean 41.5 d). The cumulative proportion of aborting cows ranged from 0.11 to 0.57 (mean 0.26) of the animals at risk. An apparent seasonal influence was noted as most abortion storms occurred during the summer and early autumn. The prevalence of antibodies to N. caninum in 50 herds which had had an abortion storm was compared with that of 100 control herds which had no history of an abortion storm. Seroprevalence was estimated by testing a 20% cross sectional herd sample using a tachyzoite lysate-based ELISA method. Seroprevalence in case herds (range 17 to 87%, mean 51.5%) was significantly higher than that in control herds (range 0 to 53%, mean 13.9%). For most herds the seroprevalence levels were equal across all age groups, which suggests that the infection had been perpetuated by vertical transmission. In these herds, the abortion storms appeared to be induced by factors causing recrudescence of a N. caninum-infection in chronically infected animals rather than being the result of a recent introduction. In 6 case herds the seroprevalence in the dairy cows was significantly higher than in the young stock, which may have been attributable to superimposed postnatal infection.
Neospora caninum is a protozoan parasite that was first described in dogs in 1988. Subsequently the parasite has been associated with abortion in cattle. Evidence is accumulating that neosporosis is a major cause of reproductive failure in cattle all over the world. Recent knowledge of neosporosis is reviewed with emphasis on the diagnosis and epidemiology of the disease in cattle. In addition, attention is paid to strategies for disease control and prevention.
Prevalence of antibodies to Neospora caninum was determined in a cross-sectional consensus survey of 1029 bovines in a dairy herd with endemic Neospora-induced abortion. Sera were screened by indirect fluorescent antibody test (IFAT). The prevalence of N. caninum antibody in the IFAT was 17.9% in 107 neonates, 26.2% in 233 yearling heifers and steers, 39.07% in 218 mature heifers, and 26.9% in 465 milking cows. Serologic reactivity was associated with production grouping on the farm with the greatest risk of serologic reactivity appearing in the yearling and mature heifers. There was an increasing risk of serologic reactivity with increasing age only in the parity one and greater animals in the herd. Castrated males were at half the risk of similarly aged females of possessing antibodies to N. caninum. There was no clear relationship between the serologic status of dams and offspring.
During the past decade, Neospora caninum infection has emerged as an important reproductive disease in cattle throughout the world. Abortion, occurring during the middle of gestation, is the primary clinical sign of the infection in cattle. Surveys in several countries from three continents have identified N. caninum infection as the major diagnosed cause of bovine abortion. Both endemic and epidemic patterns of abortion may occur in herds. An important feature of this disease is that the protozoan parasite is maintained in cattle as a chronic infection which can be passed on to the fetus during pregnancy. Two methods for the transmission of the infection in cattle have been proposed and are the subject of current investigations. Horizontal transmission utilizes a two-host life cycle whereby the cow is infected from ingestion of coccidial oocyst stages shed by the definitive host. Experimental infections have confirmed that the dog is a definitive host for the parasite. There is epidemiological evidence that the dog has a role in the prevalence of the infection but, as yet, no confirmation that the dog is the source for natural infections in cattle. Vertical transplacental transmission of the infection is an important route of infection in many herds. Vertical transmission occurs because fetal infection frequently does not result in abortion but rather the fetus survives to be a persistently infected animal. A heifer calf that is born congenitally infected is capable of transmitting the infection to the next generation when she becomes pregnant, thus maintaining the infection in the herd. The clinical outcome of transplacental fetal infection with N. caninum is likely determined by maternal and fetal immune responses which involve humoral, and most importantly, cell-mediated immune factors. The diagnosis of the infection is assisted through histopathology and immunohistochemical examination of aborted fetuses and serologic testing of cattle for evidence of infection. Several types of serologic tests, based on the use of culture-derived organisms or recombinant N. caninum antigens are available. There are no proven control methods for the prevention or treatment of neosporosis. Suggested control measures focus on programs to reduce the number of congenitally infected animals retained in the herd and to minimize the opportunity for postnatal transmission from the environment.
Cattle immunised with a POLYGEN-adjuvanted killed Neospora caninum tachyzoite preparation were previously shown to produce interferon (IFN)-gamma at levels similar to those of tachyzoite-infected cattle. In view of the critical role of IFN-gamma in resistance of mice to N. caninum infection, these results prompted us to test the POLYGEN-adjuvanted preparation in pregnant cattle to determine whether it will be able to prevent foetal infection following an experimental tachyzoite challenge. Seven heifers were immunised at 35 and 63 days of gestation with the POLYGEN-adjuvanted preparation, while five heifers were inoculated with POLYGEN alone at the same days of gestation. Four weeks later, all heifers were challenged with a combined i.v./i.m. inoculation of tachyzoites. The same challenge was given to seven unimmunized heifers at the same stage of gestation. An additional unimmunized heifer was inoculated with uninfected monolayer cell culture material. All challenged heifers, immunized and unimmunized, had infected foetuses. Immunized heifers developed both parasite-specific humoral and cellular immune responses, characterised by increased IFAT titres, a predominant IgG1 response, elevated lymphoproliferative response and IFN-gamma production. Following tachyzoite challenge, they developed an anamnestic humoral response and produced similar amounts of IgG1 and IgG2 antibodies, but did not have an anamnestic cellular immune response. The lack of anamnestic cellular immune response and/or the large i.v/i.m tachyzoite inoculum may have contributed to the failure of the preparation.
The parasite, Neospora caninum is an important cause of abortion in cattle. It is transmitted vertically or horizontally and infection may result in abortion or the birth of a live, healthy but infected calf at full-term. Only a proportion of infected cattle abort and the pathogenesis of abortion is not understood. Groups of cattle were infected with 10(7) N. caninum tachyzoites intravenously at different times relative to gestation. Intravenous inoculation was chosen to reproduce the putative haematogenous spread of N. caninum following either recrudescence of endogenous infection or de novo infection. In all cattle, infection was accompanied by high gamma-interferon and lymphoproliferative responses, and a biased IgG2 response indicating that N. caninum infection is accompanied by a profound Th1 helper T cell-like response. Infection at 10 weeks gestation resulted in foetopathy and resorption of foetal tissues 3 weeks after infection in 5 out of 6 cows. Infection at 30 weeks gestation resulted in the birth of asymptomatic, congenitally-infected calves at full term in all 6 cows, whereas the 6 cows infected before artificial insemination gave birth to live, uninfected calves. These results suggest that the reason some cows abort is related to the time during gestation when they become infected or an existing infection recrudesces.
Eighteen dairy herds with neosporosis-associated abortions were analysed for antibodies against Neospora caninum. Blood samples of all cows, heifers and calves were collected on the same day for each farm. A total of 2430 heads of cattle were examined. For each herd, the seropositive and seronegative animals were plotted against month of birth. Analysis of seroprevalence in relation to age showed an equal distribution of seropositives in all age-groups in 10 herds. In contrast, in eight herds an age-group could be identified which had a significantly higher seroprevalence than the other animals in the herd. Most seropositive animals in the high seroprevalence age-groups had either seronegative dams or seronegative offspring, whereas there was a strong relationship between the serostatus of dams and offspring in the other animals in the herd. Aborting animals were mainly part of the high seroprevalence age-group. These findings strongly indicate a post-natal infection of the animals in the high seroprevalence age-groups, probably due to a point source exposure to N. caninum.
An experiment was carried out to determine whether bovine colostrum or placenta could be a source of infection of Neospora caninum for dogs. For this purpose, two dogs were fed bovine colostrum to which culture-derived N. caninum tachyzoites were added and two other dogs were fed placental cotyledonary tissue from N. caninum seropositive cows. One dog served as a negative control during the start of the experiment but this control dog was fed cotyledonary tissue later on. None of the dogs did produce serum antibodies to N. caninum. All three dogs that were fed cotyledonary tissue did shed N. caninum oocysts, but no oocyst shedding was seen in the two dogs that were fed colostrum with N. caninum tachyzoites. Oocyst excretion did not resume in two dogs after repeated feeding of N. caninum infected placenta. The identity of the oocysts was confirmed by a bioassay in gerbils. It is concluded that ingestion of bovine placenta by dogs is an effective mode of transmission of N. caninum from cattle to dogs.
HERD HISTORY: A cluster of 19 abortions occurred in April and May 1994 on a seasonal dairy farm of 277 cows in Taranaki. Lesions consistent with neosporosis were seen in several foetuses. The age of the aborting cows ranged from 2 to 12 years. Pregnant rising 2-year-old heifers had been grazed off the main farm on a run-off' until returning in May, when they were replaced on the run-off by the rising l-year-old calves. None of these pregnant heifers aborted.
Sera were obtained from all calves (n = 32), 32 of 33 pregnant heifers, 59 of 60 3-4 year-old cows and 101 of 150 older cows, plus all cows that had aborted. Sera were tested using an indirect fluorescent antibody assay. Non-aborting cattle sera were screened at 1:400, and further dilutions were tested from 15 aborted cows.
The percentages of seropositive cattle were: 32% of the calves, 3% of the heifers, 31% of the younger cows and 27% of the older cows. The proportion of seropositive heifers was significantly lower (p< 0.01) than in the other age classes. There was no significant difference in the proportion of seropositive animals between these other age classes (p >0.05). Of the 15 cows that aborted, and for which further dilutions were tested, nine had titres of 1: 12,800, four had titres of 1:6400, one had a titre of 1: 1600 and one had a titre of 1:400. Twenty cows were the dams of pregnant heifers. Six of these cows were seropositive but all their offspring were seronegative. Fifteen aborting cows were held over to the following year when 13 became pregnant and calved normally. There were only two to three abortions in the whole herd in this following year.
These results suggest that either a point-infection occurred sometime in early 1994 with an infective period short enough so that the heifers did not get infected when they returned to the main farm, or some factor precipitated a recrudescence of latent infection with a subsequent rise in titres in about 29% of the animals on. the main farm only. Although neither hypothesis can be proven or disproven in this observational study, the former hypothesis seems more likely.