Congenital Pestivirus Infection in Sheep, Ewes, Heifers and Calves with Bovine Pestivirus Strains and Detection of Anigenic Differences between Them

Abstract

ABSTRACTSheep, ewes, cows and heifers were used in experiments for inoculation with different pestivirus strains inducing congenital infection. Intranasally and intramuscularly inoculated five groups (A-E) of seronegative sheep, ewes, goats, cattle, heifers and caws at days 49th and 126th of gestation with either of four antigenically different BVDV reference strains (OREGON C 24, NADL, OSLOSS, ALFORT-187) and one BVDV Bulgarian strain (KABLESHKOVO-76). A sixth group (F) was housed for 7 days with persistently infected calf and a seventh group (G) served as controls. From each of the experimentally groups half of the sheep and the calves were killed 2 weeks and a half of them 4 weeks after infection. All ruminants of groups were seronegative in the ELISA and in the virusneutralization test (β-procedure). At 2 and 4 weeks after infection the virus was isolated from almost all foetal organs in the all groups inoculated with different pestivirus strains. In the control group no virus was isolated from foetal organs. In experiments the sheep, ewes, goats and saws were inoculated with antigenically heterologous strains at 49th day of pregnancy. The caws and heifers were challenged at 126th day of pregnancy with homologous and one heterologous pestivirus strains (ALFORT-187). Blood samples for serology were collected on the day of inoculation, every week thereafter and on the day of killing of different groups sheep, goats, pigs and calves. Nasal swabs for isolation were taken on day 6th and day 10th after inoculation. Rectal temperatures of sheep, goats, pigs and calves were recorded daily during 14 days, starting 2 days before inoculation and clinical observation of all ewes, saws and heifers were performed daily during the experiments. From the sheep, ewes, caws, cattle, heifers and different foetuses the following organs were collected—placenta, tonsils, ovaris, pylorus, kidneys, small intestine for reisolation of using different pestivirus strains. A control group was left uninfected. The data obtained were mathematically calculated by dispersion analysis.