Bovine viral diarrhea virus and virus-neutralizing antibody titers in beef calves at or near fall weaning.

Abstract

Objective: To estimate the prevalence of bovine viral diarrhea virus (BVDV) infection in spring-born beef calves, at or near fall weaning, and assess how concentrations of BVDV Type 1 and Type 2 antibodies near weaning varied among BVDV vaccination programs.

Animals: Serum was collected from 1934 beef calves in 107 herds in the Canadian Cow-Calf Surveillance Network (C3SN).

Procedure: Reverse transcription real-time polymerase chain reaction was used to detect BVDV infection, and serum virus neutralization assay measured antibody concentrations for BVDV Type 1 and Type 2. Records of BVDV vaccine use were available for nursing calves and cows within the past year from 95 herds. Mixed regression was used to estimate the association between herd vaccination status and antibody concentrations.

Results: Overall, 0.2% of calves and 2.8% of herds were positive or suspect for current BVDV infection. Median serum virus neutralization BVDV Types 1 and 2 titers were 54 and 108, and 19% of calves had undetectable titers. One in 3 calves had titers ≥ 324 and < 6% had titers ≥ 8748. In the 95% of herds in which cows had been vaccinated against BVDV, calves that received 1 or 2 doses of BVDV vaccine pre-weaning (80%) were more likely (P < 0.02) to have BVDV Types 1 and 2 titers ≥ 324 near weaning compared to unvaccinated calves.

Conclusion and clinical relevance: Although the overall low prevalence of persistently infected calves was similar to that in previous reports, BVDV antibody titers were higher and the herd-level prevalence of BVDV infection was lower than in previous reports. Herd-level prevalence of BVDV infection was lower in Canadian beef herds that commonly administered BVDV vaccination to both cows and nursing calves. Calves from vaccinated herds also had significantly higher BVDV Type 1 and Type 2 titers at weaning, suggesting reduced risk from transient infection.