Bovine viral diarrhea virus (BVDV) is an important reproductive pathogen of cattle worldwide. The reproductive outcome of BVDV infection is largely dependent on the immune status of the dam and the stage of gestation at the time of infection. Potential sequelae include failure of conception, abortion, a variety of congenital malformations, and fetal infection. Vaccination is a possible tool in the control of BVDV, and there has been a recently renewed focus on providing fetal protection through vaccination. Consequently, the aim of this study was to evaluate the efficacy of BVDV vaccination to prevent reproductive disease by performing a quantitative synthesis of previously published studies.
Pertinent articles to be included in the analysis were identified by performing a search in four relevant scientific databases (PubMed, CAB abstracts, National Agricultural Library catalog, and Web of Science) and examining the reference lists of 10 germane review articles. Inclusion criteria for the meta-analysis mandated that the studies were controlled, primary studies that included necessary data for use in the meta-analysis (e.g., group size, number of abortions). Forty-six studies in 41 separate articles matched the inclusion criteria. Risk ratio effect sizes were used in random effects, weighted meta-analyses to assess the impact of BVDV vaccination on three outcomes: risk of fetal infection, abortion risk, and pregnancy risk. Within each outcome, subanalyses were performed to evaluate the effect of a variety of interventions, including modified live, inactivated, polyvalent and monovalent vaccination, homologous, heterologous, or field challenge, and studies with only bovine subjects.
The analysis revealed a decrease in abortions of nearly 45% and a nearly 85% decrease in fetal infection rate in cattle vaccinated for BVDV compared with unvaccinated cohorts. Additionally, pregnancy risk was increased by approximately 5% in field trials of BVDV vaccinates. This meta-analysis provides quantitative support for the benefit of vaccination in the prevention of BVDV-associated reproductive disease.