A systematic effort to control or even eradicate bovine viral diarrhea virus (BVDV) in the United States will require far-reaching education and market-based incentives. That message was clear from a presentation from Auburn University veterinarian Dan Givens, DVM, PhD, when he discussed control strategies during this week’s international symposium on BVDV and related pestiviruses.
Several presenters had outlined European programs, such as in Scandinavia and Germany, where systematic testing, culling and continued surveillance, sometime with and sometimes without support of vaccinations, have significantly reduced or virtually eliminated occurrence of the disease. Those programs though, have taken place in countries with smaller livestock populations, smaller geographic areas and less segmented livestock industries. And in those countries, government typically became involved at some stage in the control program with regulations and/or financial support such as indemnity payments for producers culling calves identified as persistently infected (PI) with BVDV.
Givens explained how in the United States, with distinct cow-calf, stocker and feedyard sectors, and cattle typically changing ownership several times as they pass through the production system, our challenges are different from those in Europe. Here, about nine percent of cow-calf operations control about 51 percent of the total cow herd, and the five largest cattle-feeding operations control about 20 percent of cattle on feed. The remaining cattle, particularly at the cow-calf level, are in control of small operators who, in general, receive little information about diseases such as BVD. Data from the USDA’s National Animal Health Monitoring System (NAHMS) 2007 survey show that 15 percent of cow-calf producers had never heard of BVDV. And while 29 percent indicated they were fairly knowledgeable on the topic, only 4.2 percent had tested any of their cattle for the disease in the previous three years. Among producers with 200 or more head of cows, the percent who had tested cattle for BVDV increased to 15.6.
In that same survey, 28 percent indicated they vaccinated cows, 25 percent vaccinated replacement heifers and 33 percent vaccinated calves against BVDV. Among those who vaccinated replacement heifers, about half used killed-virus vaccines and half used modified-live vaccines.
A systematic control program in the United States would likely require strategic vaccination, biosecurity protocols and testing and culling to remove PI animals, which serve as the source of ongoing infections in herds and throughout the marketing and production system. Economics, animal-welfare concerns and pressure to reduce antibiotic use all provide justification for a control or eradication effort, but producers in many cases do not recognize the value.
BVD outbreaks in cow-calf herds are, in some cases, economically devastating, with catastrophic numbers of abortions and pre-weaning death loss in calves. But in other cases, the virus can be prevalent in the herd without dramatically noticeable effects. Producers might believe they do not have BVD in their herd because they do not see a high incidence of diarrhea, but the virus can manifest in a range of sub-clinical losses in terms of performance and reproduction.
Givens expressed concern that as the industry enters an expansion phase, and producers introduce replacement heifers from outside sources without testing or quarantine, large, damaging outbreaks could become more common over the next few years.
Participants in the symposium generally agreed that government support, including either indemnity payments for culling of PI calves or regulations governing testing and culling is unlikely and probably undesirable. Instead, we’ll need market-driven incentives for control at the cow-calf level, based on a recognition that tested, BVDV-free cattle carry a premium value in the marketplace.
More education will be required, but those incentives have emerged in recent years and likely will continue to grow. Data from over 400,000 cattle marketed through Superior Livestock Auctions in 2013 showed an average premium of $2.97 per hundredweight for calves identified as BVD-PI free. For a 600-pound calf, that meant an advantage of $17.82 per head. After subtracting the cost of testing, Producers netted at least $14 per head. Those premiums are likely to grow as the high value of feeder cattle and finished cattle pressures stocker operators and cattle feeders to minimize risk as much as possible. And from an animal-health standpoint, they increasingly realize one of the best ways they can reduce risk is to keep BVD-PI cattle out of their operations.