Identification of bovine viral diarrhoea virus in persistently infected immunotolerant cows in herds of the Region Metropolitana, Chile

Abstract

The presence of immunotolerant, persistently infected (IPI) animals with bovine viral diarrhoea virus (BVDV) was detected in several milking herds with abortions, repeat breeders, still births and poor growth rates, by the virus isolation test and measurement of serum neutralising antibodies, in 2 blood samples from each animal. Samples were taken 3 month apart.

Virus isolation was done by inoculation of the plasma and lymphocytes from peripheral blood in primary bovine testicle cell culture. The isolates were identified, on the second serial passage, by the indirect immunoperoxidase test. Cows were considered IPI when BVDV was isolated in the two blood samples and serum title neutralising antibodies were <8.

BVDV was isolated twice from 42 cows out of 238 (18% IPI). 22/34 herds had IPI animals (65%). There were differences in the frequency of isolations (p>0.05) in age averages between IPI and non IPI cows. 
It is concluded that isolations of BVDV were high and that there is a high frequency of IPI cows in dairy herds from the Region Metropolitana in Chile, suspected of carrying IPI animals.