When dealing with individual cow-calf herds, and before a whole-herd BVDV testing regimen is implemented, the herd veterinarian should assess the probability of the herd possessing a PI animal. Although BVDV has the potential to inflict severe negative economic consequences throughout all phases of the beef and dairy industries, the reality of BVDV epidemiology in the cow-calf segment is that only approximately 8.8% of U.S. cow-calf herds are infected (National Animal Health Monitoring Service, 2008). “Publicized BVDV outbreaks, the complexity of the disease and the novel disease reservoir of persistently infected (PI) cattle has permitted BVDV to garner a high degree of exposure among veterinarians and producers,” says Jason Nickell, DVM, PhD, Dipl. ACVPM, Bayer Animal Health. “Additionally, numerous BVDV tests are currently available which easily facilitates implementation of testing regimens.”Whole-herd testing is expensive, and should be used strategically in herds where veterinarians feel the risk is high enough to warrant the cost.
As stated above, testing costs money. However, if it can identify individual animals whose removal from the herd can benefit it economically, it has a high value. If it’s implemented in negative herds that do a good job of biosecurity and have little risk, it’s money that may have been better spent to improve upon other disease control or production measures. In 2011 Nickell et al published a study in the Journal of Veterinary Diagnostic Investigation using stochastic models to look at the economic viability and value of different types of BVDV testing strategies in different herd situations.
The cost of individual-animal BVDV testing can range from $4-$7/head, and the producer’s initial financial investment can be significant in larger herds. “Our data suggests that as test cost increases, economic value of whole-herd VDV testing decreases,” Nickell says. “However, as the pre-test probability of a herd being BVDV positive or herd prevalence in a population increases, the negative influence of test cost on the overall value of whole-herd testing is reduced.” This is likely due to an increase in the probability of detecting a PI animal and reducing the negative influence of BVDV in the herd. The testing strategy paid for itself when herds are positive.
The low cow-calf herd prevalence coupled with a high variability of potential clinical outcomes calls into question the economic sustainability of instituting whole cow-calf herd testing programs across either large populations or in individual cow-calf herds without strong signs of BVDV infection.