Figure 7 - uploaded by Piet A. van Rijn
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Microphotograph of cerebral remnant of stillborn 9-month-old calf with hydranencephaly. Small rim of cerebral parenchyma composed of loosely arranged glial cells with leptomeninges and covered at the inside by ependymal cells.
Source publication
Following the detection in Northern Ireland of bluetongue serotype-8 (BTV-8) PCR-positive calves born from PCR-negative but seropositive heifers imported from the Netherlands, an investigation was started to determine whether PCR-positive calves were born in the first quarter of 2008 in the Netherlands. Blood samples were collected on 43 dairy farm...
Context in source publication
Context 1
... concordance with the results of experimental infection of foetuses between 85 and 125 days of gestation (11,13), our findings indicate that the infection with btv-8 with hydranencephaly, the inner side of the rim of cerebral tissue was covered with ependymal cells (Figure 7). In three foetuses, pcr-positive for btv and without gross lesions, histological lesions were present in the brain, consisting of multiple areas of malacia in the cerebral white matter, calcium deposits, and foci of inflammatory cells. ...
Citations
... Transplacental transmission of BTV8 based on field data was reported to range from 16% [105,106] to 35% [107,108]. In experimental infections, passage of BTV8 from the mother to the foetus could be demonstrated in 43% of infected ewes whereas BTV1 could be detected in up to 67% of the foetus [59]. ...
Starting in 2006, bluetongue virus serotype 8 (BTV8) was responsible for a major epizootic in Western and Northern Europe. The magnitude and spread of the disease were surprisingly high and the control of BTV improved significantly with the marketing of BTV8 inactivated vaccines in 2008. During late summer of 2011, a first cluster of reduced milk yield, fever, and diarrhoea was reported in the Netherlands. Congenital malformations appeared in March 2012 and Schmallenberg virus (SBV) was identified, becoming one of the very few orthobunyaviruses distributed in Europe. At the start of both epizootics, little was known about the pathogenesis and epidemiology of these viruses in the European context and most assumptions were extrapolated based on other related viruses and/or other regions of the World. Standardized and repeatable models potentially mimicking clinical signs observed in the field are required to study the pathogenesis of these infections, and to clarify their ability to cross the placental barrier. This review presents some of the latest experimental designs for infectious disease challenges with BTV or SBV. Infectious doses, routes of infection, inoculum preparation, and origin are discussed. Particular emphasis is given to the placental crossing associated with these two viruses.
... In the past, BTV transplacental transmission was associated with laboratory-adapted strains, in particular live attenuated vaccine virus strains [23,24]. The results of this field study conducted on a large number of abortions support the findings of European studies regarding the transplacental transmission of BTV-8 in cattle [12][13][14][15][16][17]25,26] . The 16% of BTV-8-positive fetuses/calves found in this study is comparable to the 18.5% BTV-8-positive fetuses from dams with no suspicion of BT, reported by De Clercq et al [12]. ...
During the incursion of bluetongue virus (BTV) serotype 8 in France in 2007, an increase in the number of abortions in cattle was observed, but the cause was not clearly established. A survey of all the reported cases of abortion in cattle from November 2008 to April 2009 was conducted in the Nièvre district (Burgundy region) to determine the percentage of abortions as a result of BTV-8 and to study factors that could have played a role in BTV-8 transplacental transmission. BTV-8 was present in 16% of the fetuses or newborn calves that died within 48 h, from 780 dams. Dams inseminated before the BTV epizootic peak recorded from July to September 2008 were more likely to have BTV-positive abortions (OR=5.7, P<0.001) and those vaccinated in May or June 2008 were less likely to have BTV-positive abortions (OR=0.3, P=0.01 and OR=0.4, P=0.001, respectively). The gestational month was not a predictor of BTV abortion. In blood or spleen, fetuses/calves from RT-PCR-positive dams had significantly higher RNA concentrations than fetuses/calves from RT-PCR-negative dams. Of the 128 dams that had BTV-positive fetuses or calves, 60% were RT-PCR-negative. BTV-8-positive fetuses/calves were significantly more frequent (n=42 vs n=21, P=0.082) amongst those showing clinical signs or lesions suggestive of cerebral damage.
... It was concluded that, after viral adaptation to cell culture, BTV field strains can cause fetal infection (Flanagan and Johnson, 1995). Recent field studies Desmecht et al., 2008;Menzies et al., 2008;van Wuijckhuise et al., 2008;Wouda et al., 2009) and an experimental study (Backx et al., 2009) indicate transplacental fetal infection by BTV-8. So, there is evidence for fertility disorders associated with transplacental infection by BTV-8. ...
A major epidemic of bluetongue virus serotype 8 (BTV-8) occurred in Western Europe in 2006. During 2007 it became evident that BTV-8 had survived the winter and a re-emerging epidemic quickly developed. The objective of this study was to describe the severity and clinical impact of the BTV-8 epidemic in 2007 in The Netherlands in laboratory-confirmed outbreaks and to compare this with the situation in 2006. The relative frequency of clinical signs in BTV-8 affected sheep flocks and cattle herds in 2007 and 2006 was similar. The most prominent changes were a higher proportion of sheep flocks with lameness and a much higher proportion of cattle herds reporting a decrease in milk yield in 2007. BTV-8 associated morbidity and mortality incidence rates in sheep flocks and cattle herds were significantly (P<0.001) higher in 2007 than in 2006. Both in sheep flocks and cattle herds, BTV-8 associated case fatality was significantly (P<0.001) lower in 2007, which was probably due to better medical treatment of sick animals. There were significantly (P<0.001) more fertility problems associated with BTV-8 infection in outbreak cattle herds in 2007 compared to 2006.
... Experimental infection with btv8\ net2006 of 8-month pregnant cows resulted in pcr-positive calves and clinical signs of bluetongue in one of seven calves (2). On the other hand, apparently intrauterine infection with btv8\net2006 does not result in developmental defects per se, since healthy calves that are pcr-positive for btv and selected for breeding were identified in the vector-free period (15,26). Up to 25% of the dams of pcr-positive calves and bluetongue-seropositive calves reported by Wuijckhuise et al. (26) were probably infected during the first half of gestation, and therefore these calves may have been exposed during the critical period (L. ...
... On the other hand, apparently intrauterine infection with btv8\net2006 does not result in developmental defects per se, since healthy calves that are pcr-positive for btv and selected for breeding were identified in the vector-free period (15,26). Up to 25% of the dams of pcr-positive calves and bluetongue-seropositive calves reported by Wuijckhuise et al. (26) were probably infected during the first half of gestation, and therefore these calves may have been exposed during the critical period (L. van Wuijckhuise, personal communication). ...
An outbreak of hydranencephaly in aborted foetuses and newborn calves occurred following the 2007 epidemic of bluetongue serotype 8 (BTV8\net2006) in the Netherlands. In total 35 aborted foetuses and 20 live-born calves, submitted from September 2007 to May 2008, were examined pathologically. Foetuses with gestational ages between 4 and 9 months (mean 6.8 month) showed varying stages of cerebral malformation. Initial stages were cavitations in the cerebral hemispheres with massive destruction of neuroparenchyma, calcium deposits, and a phagocytic inflammatory response. Later stages showed distinct hydranencephaly, the cerebral hemispheres being almost completely replaced by fluid-filled sacs. In seven cases the cerebellum was affected as well, but brainstem structures were intact. Newborn calves with clinical signs of abnormal behaviour ('dummy calves'), circling, head pressing, incoordination, and blindness were seen from the end of January 2008. The calves were born between 2nd January and 16th March 2008. The calves were euthanized after 1 day up to 14 weeks (mean 4-7 weeks). Brain malformations in these calves were confined to the cerebrum and consisted of varying degrees of hydranencephaly. Spleen tissue was PCR-positive for bluetongue virus (BTV) in 21 of 35 foetuses and in 1 of 20 calves. A higher percentage of PCR-positives was found in foetuses aborted in early gestation than in late gestation, suggesting clearance of BTV during gestation. Fifteen of 33 dams of PCR-negative hydranencephalic foetuses or calves could be traced and all were BTV-seropositive, indicating a previous BTV infection. The timing of hydranencephaly cases in live-born calves during the first months of 2008 was consistent with infection in early gestation during the prior transmission season. Vertical transmission and teratogenic potential have previously been described for modified-live vaccines for bluetongue but are highly unusual for field strains of BTV, which raises the issue whether BTV8\net2006 or its ancestor has been cell- or laboratory-adapted in the past.
... Culicoides species, principally C. dewulfi, the Obsoletus complex, and recently found C. chiopterus, can be infected with BTV-8 (Dijkstra et al., 2008;Mehlhorn et al., 2007;Meiswinkel et al., 2007) and might turn out to be competent vectors. The distinct feature that BTV-8 survives the winter by passing from pregnant infected ruminants to their offspring while in utero, is raised following observations in the Netherlands and Northern Ireland in March 2008 that PCR-positive ruminant offspring were born to dams that were infected with bluetongue virus the previous year (Menzies et al., 2008;van Wuijckhuise et al., 2008), and by a Belgian study of cattle and sheep in the field . Additionally the reports of aborted and newborn calves from BTV-8 infected dams with severe developmental defects of the brain, i.e., hydranencephaly, prove natural vertical transmission of the European strain of BTV-8 (De Clercq et al., 2008;Vercauteren et al., 2008). ...
Bluetongue virus (BTV) is an arthropod-borne virus infecting domestic and wild ruminants. Infection in cattle is commonly asymptomatic and characterised by a long viraemia. Associated with the emergence and the recrudescence of BTV serotype 8 (BTV-8) in Northern and Central Europe, remarkable differences have been noticed in the transmission and in the clinical expression of the disease, with cattle showing clinical illness and reproductive disorders such as abortion, stillbirth and fetal abnormalities. Several investigations have already indicated the putative ability of the European BTV-8 strain to cross the bovine placenta and to cause congenital infections. The current epidemiological and pathological findings present an unusual picture of the disease in affected bovines.
Potential vertical transmission of wild-type bluetongue virus serotype 8 (BTV-8) in cattle was explored in this experiment. We demonstrated transplacental transmission of wild-type BTV-8 in one calf and oral infection with BTV-8 in another calf. Following the experimental BTV-8 infection of seven out of fifteen multi-parous cows eight months in gestation, each newborn calf was tested prior to colostrum intake for transplacental transmission of BTV by RRT-PCR. If transplacental transmission was not established the calves were fed colostrum from infected dams or colostrum from non-infected dams spiked with BTV-8 containing blood. One calf from an infected dam was born RRT-PCR positive and BTV-specific antibody (Abs) negative, BTV was isolated from its blood. It was born with clinical signs resembling bluetongue and lived for two days. Its post-mortem tissue suspensions were RRT-PCR positive. Of the seven calves fed colostrum from infected dams, none became infected. Of the six calves fed colostrum from non-infected dams spiked with infected blood, one calf became PCR-positive at day 8 post-partum (dpp), seroconverted 27 days later, and remained RRT-PCR and Abs positive for the duration of the experiment (i.e., 70dpp). This work demonstrates that transplacental transmission in late gestation and oral infection of the neonate with wild-type BTV-8 is possible in cattle under experimental conditions.
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