Figure 1 - uploaded by Maricel Guzman
Content may be subject to copyright.
Context in source publication
Similar publications
Citations
... Tradicionalmente, los pequeños rumiantes se han considerado los hospedadores naturales del H. contortus, mientras que los bovinos lo son para el H. placei. Estudios experimentales con infecciones establecidas de larvas con la especie H. contortus, han demostrado que el número de larvas capaces de instaurarse y llegar a completar el ciclo es mucho menor en bovinos que en ovinos (7,16 vs 28,8%); por ello se considera a los bovinos mucho más resistentes para dicha especie de Haemonchus que los pequeños rumiantes 13 . Sin embargo, ambas especies de Haemonchus (contortus y placei) son igual de patógenas en terneros por presentar tasas de infección similares de alrededor del 7% 8,9 , y existen reportes que implican al H. contortus en casos de mortalidad en terneros 15,23 . ...
Haemonchosis is a parasitic disease that in cattle, unlike small ruminants, rarely causes mortality. However, parasitic burdens that are usually subclinical in well-fed calves may become clinical causing death when body condition is poor. This report describes a case of fatal haemonchosis in a 7-month-old Brahman calf and the results of treatment with albendazole (10 mg/kg PO) in 17 cohort calves. The farm, dedicated to breeding and rearing beef calves, was located in the high tropics of the Andes, municipality of Yarumal (Antioquia), at 2,353 meters of altitude with an annual mean temperature of 14 °C. Apart from vaccination for foot and mouth disease, the animals are not subjected to any other treatments. The diagnosis was initially suspected based on clinico-pathological observations of a severe anemia with hypoproteinemia of non-inflammatory etiology, and was confirmed in the postmortem examination by the presence of hundreds of adult nematodes of Haemonchus spp. in the abomasum and a count of 19,200 eggs per gram of feces (EPG) of trichostrongylids. Stool culture showed that 70, 20, and 10% of these eggs belonged to Haemonchus, Coperia and other nematode genera, respectively. Albendazole treatment was effective in reducing parasitic loads in 17 treated calves from moderate (200-700 OPG) and high levels (> 700 EPG) to low levels (16-100 EPG). The infection was completely eliminated in half of the treated animals and was reduced to below 90% in only 3 animals. Because the mean egg reduction percentage was 95%, it can be inferred that there is no resistance to albendazole. In conclusion, this case reveals that haemonchosis should be included in the differential diagnosis of mortality in calves in the Colombian tropics, and that necropsies and periodic coprological examinations are necessary to establish preventive and control measures of this parasitosis.
In order to evaluate the potential risk of Haemonchus contortus resistant to benzimidazole (BZ) treatments to pass from sheep to cattle a series of experiments were carried out. Two field isolates of H. contortus resistant (Ayacucho) or susceptible (Cedive) to BZ treatments were reproduced in lambs and involved in the study. Two groups of 4 calves each and two groups of 4 lambs each were infected with larvae (L3) of each isolate respectively. The number of eggs in faeces (EPG), worm count and ratio of worm establishment (RWE) were determined. The number of red blood cells, packed cell volume and haemoglobin concentration was assessed. The EPG levels were higher for Ayacucho isolate which reached to a peak of 7,168 and 780 at day 42 post inoculation (PI) in lambs and calves respectively. The RWE at day 45 PI was 28.8 % and 7.16% for Ayacucho isolate in lambs and calves respectively while for Cedive isolate was 36.6% and 0.04% respectively. At day 90 PI the RWE was of 1.94% and 0.69% in lambs for Ayacucho and Cedive isolate respectively, whereas no worms were recovered from calves. The haematological parameters in lambs and calves did not show significant differences between isolates. The present studies demonstrate that some populations of H. contortus may complete life cycle in calves and remain established for at least a 45 days period PI. This finding should be strongly considered when farm production involves mixed or alternate sheep/cattle grazing and backgrounds of anthelmintic resistance.
