Exacerbation of experimental parvoviral enteritis in calves by coccidia and weaning stress.

The disease induced in calves following oral dosing with bovine parvovirus (BPV) was found to be substantially exacerbated when the animals had subclinical coccidiosis. Low levels of passive serum antibody appeared to have little influence on the response to BPV. Imposition of weaning stress on coccidia-infected calves which had apparently recovered from prior infection with BPV, was found to induce severe diarrhoea with recrudescence of BPV excretion in faeces. This was in marked contrast to the relatively mild diarrhoea which was found following weaning of control animals and animals infected with either agent alone. It was concluded that BPV activity and damage in the intestinal tract was probably enhanced as a consequence of the extra mitotic activity induced in the region by coccidial infection and the local effects of weaning. On the basis of these and previous findings in the field, it is suggested that BPV may play a significant role in the aetiology of post-weaning diarrhoea in calves.