Submitted to: Conference Research Workers Disease Meeting
Publication Type: Abstract only
Publication Acceptance Date: 9/4/2005
Publication Date: 9/4/2005
Citation: Braun, L.J., Holler, L.D., Ridpath, J.F., Neill, J.D., Chase, C.L. 2005. Virological analysis and serological response in cattle persistently infected with type 2a bovine viral diarrhea virus (BVDV) [abstract]. 86th Annual Meeting of the Conference of Research Workers in Animal Diseases. p. 141. Interpretive Summary:
Technical Abstract: Fetal infection with non-cytopathic bovine viral diarrhea virus late in the 1st trimester or early in the 2nd trimester frequently results in persistent infection (PI). Forty-four calves were identified as BVDV positive based on immunohistochemistry staining of ear notch samples. Thirty-nine calves were transported to a university facility in September 2004. Subsequent testing revealed that 36 of the animals were positive by virus isolation and ear notch. The viruses isolated from these 36 animals were greater than 99.5% similar based on comparison of the 5 UTR. These animals were bled at 3-month intervals over a 9-month period and samples analyzed for virological and serological changes. Comparison of 5 UTR and E2 region sequenced revealed that the viral population within an individual PI was stable over time. However, there were conserved differences between animals observed in the E2 coding region. These were not a continuum of differences, but a clear subgroup of 9 calves that had conserved variant motifs. Twenty-four of the calves succumbed to mucosal disease during the experiment and CP-BVDV virus was isolated from 18 calves. The animals died from May to August 2005 in three major groups. The CP-BVDV is currently being sequenced to determine mutation differences. The 3 animals, from which virus could not be isolated, had initial titers against BVDV ranging from 4096 to 8192. Titers decreased 4-8 fold 3 months later. Six of the PI animals developed SN titers against type 2 BVDV that remained stable over a 3-month period ranging from 1:8-1:256. There was no relationship between the development of antibody and onset of mucosal disease. These results indicate that: 1. Acutely infected animals born during/following a BVDV outbreak may be positive by IHC 2. Nonvaccinated PI animals may develop titers against BVDV 3. The viral population (swarm) within a PI animal is stable over time, however, PI animals born during an outbreak may have variant populations.