1a.Objectives (from AD-416)
Objective 1. Document the pathogenesis of BVDV in offspring of deer infected during pregnancy.
Objective 2. Study the transmission of BVDV from persistently infected cervids to cattle.
1b.Approach (from AD-416)
The overall goal of this application is the determination of the role of white-tailed deer as reservoirs of BVDV for domestic cattle. Our research objectives are:
1) Document the fetal pathogenesis resulting from BVDV infection of pregnant does.
2) Determine the ability of BVDV persistently infected deer to transmit BVDV to cattle or deer.
To meet our research objectives we will infect pregnant white-tailed deer with BVDV in order to generate persistently infected (PI) fawns. To study transmission between cattle and deer we will expose BVDV naive cattle to fawns directly, to contaminated housing, or to contaminated feed.
This project generates information regarding bovine viral diarrhea virus (BVDV) infection in deer as it links to objective 1 of the inhouse project. Bovine viral diarrhea viruses cause either short-term (acute) or life-long (persistent) infections in cattle. Persistently infected cattle are one of the major means by which BVDV is spread from herd to herd. Pregnant deer, in the first, second, and third semesters of pregnancy, were infected with a BVDV2 strain, isolated from deer, and pregnancy outcomes monitored. The results of these studies indicated that BVDV infections result in reproductive disease in deer that is very similar to the reproductive disease observed in cattle. This suggests that similar control programs can be used for reducing BVDV infection in cattle and deer. As cattle and deer populations in the U.S. are in frequent contact it appears that it will be necessary to control BVDV in both populations in order to reduce BVDV infections in cattle. Two reports detailing these studies have been published in peer-reviewed journals and another report has been submitted to a peer-reviewed journal. Three rounds of a study evaluating transmission of BVDV from deer to cattle by indirect contact following acute infection of deer were conducted. These experiments demonstrated the transmission of BVDV from acutely infected deer to cattle via shared feeding equipment and housing. The significance of these studies is that they demonstrate that wild deer could transfer BVDV from one domestic cattle herd to another by using feed bunks and salt licks and sharing pasture. A talk detailing these acute transmission studies was presented at a bovine practitioners' meeting. In addition to the studies described above, primary cell lines derived from white-tailed deer fetuses were generated and a comparison has been conducted of BVDV strains isolated from deer to those isolated from cattle. Progress has been monitored by bi-yearly onsite visits by a cooperating South Dakota State University scientist.