COUNTERMEASURES TO CONTROL AND SUPPORT ERADICATION OF BOVINE VIRAL DIARRHEA VIRUS (BVDV)
Location: Ruminant Diseases and Immunology Research Unit
Title: Characterization and detection of BVDV related reproductive disease in white tail deer
Submitted to: World Association of Veterinary Laboratory Diagnosticians
Publication Type: Proceedings
Publication Acceptance Date: August 10, 2007
Publication Date: November 11, 2007
Citation: Ridpath, J.F., Driskell, E., Chase, C.C., Neill, J.D. 2007. Characterization and detection of BVDV related reproductive disease in white tail deer. In: Proceedings of the 13th International World Association of Veterinary Laboratory Diagnosticians Symposium, November 11-14, 2007, Melbourne, Australia. p. 34.
Bovine viral diarrhea viruses (BVDV) are the causative agent of reproductive and respiratory disease in cattle resulting in significant economic loss to the beef and dairy industries. The primary consequences of reproductive infection are due to the direct infection of the fetus and the outcome depends on the stage of gestation in which the fetal infection occurs(1). Although abortions and weak calves have been attributed to BVDV infection in late gestation(6), infections occurring earlier in gestation generally have greater impact. Fetal infections in cattle, occurring during the first trimester, result in fetal reabsorption, mummification, abortion or the establishment of persistently infected (PI) animals. PI cattle are considered the main vector for introduction of the virus to naive herds.
BVDV also replicates in white-tailed deer (Odocoileus virginianus) (2-5). Free ranging white-tailed deer populations are frequently in contact with domestic cattle in the U.S., therefore, possible transfer of BVDV between cattle and deer has significant implications for proposed BVDV control programs. The goal of this study was to examine the effects of BVDV infection in pregnant white-tailed deer
Material & methods
Eleven white-tailed does were purchased from a commercial breeder and housed in BSL2 containment. Pregnancy status was confirmed and the calculated stage of pregnancy was based on date of contact with buck. Does were inoculated with one of two BVDV previously recovered from wild white-tailed deer. Levels of BVDV neutralizing serum antibodies were determined prior to inoculation and 21 or 35 days post inoculation. Virus isolation was performed on tissues from aborted fetuses, tissues from does that died and from blood samples from live fawns. Additionally, ear notches of live fawns were tested for BVDV antigen by antigen capture ELISA (ACE).
Two of the does had serum antibody titers against BVDV (equal to or >512) prior to inoculation, the remaining 9 does were seronegative. Both seropositive animals gave birth to normal fawns. Of the remaining 9 seronegative animals, one was not pregnant at the start of the study, four died (death between 8 to 79 days post inoculation), one apparently readsorbed its fetus, two aborted and one gave birth to two probable PI fawns. BVDV was isolated from fetuses, maternal tissues and PI fawns. Ear notches of PI fawns were positive by ACE.
Discussions & conclusions
Following BVDV infection of deer we confirmed infection of fetuses within the first 7-8 days of infection. We observed abortion and mummification following infection and the birth of apparently persistently infected fawns. The fawns of does that had serum neutralizing antibodies against BVDV at the time of inoculation were protected. These observations are consistent with the clinical presentation of BVDV associated reproductive disease in cattle following exposure before 125 days gestation. Further research needs to be done to determine if the similarities between BVDV associated reproductive disease in white-tailed deer and cattle hold at later stages of gestation and to determine, more exactly, the window of fetal vulnerability for development of persistent BVDV infection in white-tailed deer.
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