Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 3, 1997
Publication Date: N/A
Interpretive Summary: Infection with bovine viral diarrhea virus (BVDV) results in significant economic losses for U.S. cattle producers. Elimination of BVDV from cattle herds is complicated by the existence of animals that have life-long BVDV infections. These animals are a source of infection for other animals they come in contact with. The purpose of this study was to determine if the levels of BVDV these animals produce is constant or changes with age or condition. It was found that the virus was hard to detect in nursing calves but was easily detected after the animals were weaned. This was because maternal antibodies in milk masked the presence of virus. It was also found that over a lifetime some animals made antibodies against BVDV. These antibodies decreased the amount of virus found in the animal's blood stream but did not eliminate it. These findings provide two explanations for the failure of efforts to detect and remove infected animals from U.S. herds. This research contributes to the efforts of producers and veterinarians to improve herd health and production efficiency.
Technical Abstract: Virus isolation and serum neutralizing antibody titers were determined over a period of time from samples collected from animals persistently infected with bovine viral diarrhea virus. To compare the ability to detect bovine viral diarrhea virus by virus isolation from serum or white blood cell preparations, 4 persistently infected calves were monitored from birth until 70 days of age. In 3 of 4 persistently infected calves virus isolation from serum and white blood cells was negative until approximately 42 days of age when colostral antibody had declined. The level of viremia in 7 adult (>12 mos.), persistently infected animals decreased by one ten-fold dilution over a least a two-year period. The level of viremia became undetectable by virus isolation from serum in one animal out of the seven examined. This decline was associated with the development of virus neutralizing antibody. Although the level of viremia is fairly stable within persistently infected animals, the presence of specific neutralizing antibody may affect the ability to isolate bovine viral diarrhea virus. These findings are important when considering diagnostic testing to identify persistently infected animals by virus isolation.