BVDV Control Requires Integrated Approach
BVDV Symposium producer session, Jan. 27, 2009
PHOENIX, Ariz. (Jan. 27, 2009) — An integrated approach is essential to controlling bovine viral diarrhea virus (BVDV), emphasized Dan Grooms, a veterinarian and associate professor in the Department of Large Animal Clinical Sciences at Michigan State University, during his presentation to attendees at the applied science session of the 2009 BVDV Symposium Jan. 27, 2009, in Phoenix, AZ.
“The beef industry is moving toward raising the bar on BVD control – with the eventual goal of eradication in North America,” said Grooms. He noted that several bull tests and livestock shows now require BVD testing, and many private seedstock operations test bulls for the virus and advertise that their sale offering is free of the disease.
Grooms explained that persistently infected, or PI, animals are the major source of spread of the BVD disease. A PI calf is created if it is exposed to BVDV as a fetus between Day 40 and Day 125 of gestation. These animals then carry and shed the disease for life.
Studies have shown the effects of a PI animal within a cow-calf herd can decrease pregnancy rates by 5% and cost $14-$25 per year per head in decreased returns.
At the feedlot, a PI animal can increase morbidity rates, and one study showed the cost of exposure to a PI animal to be $41-$93 per animal exposed. “So there’s a significant economic impact if we don’t control BVD,” Grooms said.
Controlling BVD within the herd — and the industry, Grooms said, could increase productivity, increase economic return, decrease health risk, and increase animal welfare.
He suggested a four-step approach to BVD control:
1. Understand herd goals and risk tolerance. Grooms said how much risk a producer is willing to tolerate and the goals of the operation will dictate the type of control program that is implemented. For instance, a diagnostic testing program for an operation that focuses on selling replacement heifers would be conducted differently than a testing program designed to clean up BVD in an infected herd.
2. Develop a prevention control plan. A control plan should reduce the risk of BVD entering the operation — primarily through biosecurity methods. To design such a plan, operators need to understand the sources of BVDV exposure, such as through fenceline contact with other herds, exposure to wildlife, or, Grooms notes that commonly animals being brought into the operation may carry a transient or persistent BVD infection. This means bulls, replacements, show cattle, embryo recipients and semen should be considered potential sources of the disease.
3. Identify and eliminate PIs. “There are a lot of effective tools to detect BVD infection,” Grooms said. Among the options are the ELISA blood tests, the IHC skin ear notch test, or PCR pooled tests that use skin or blood samples. If PI animals are found, they should be removed from the herd.
4. Improve herd immunity. Immunizing cattle against BVD through vaccination is also an important tool to help control BVD. Grooms reported there are more than 150 BVD vaccines or vaccine combinations available commercially. “So the vaccines can be used in a variety of different management settings,” he said. He also shared that in most studies where a modified-live vaccine (MLV) was used, the ability to protect the fetus from BVD appeared to be greater.
However, he cautioned that vaccines should not be viewed as a silver bullet. “Vaccines are not 100% effective in preventing BVD infection. They are a useful tool, but not the only answer to controlling BVD,” he concluded.
Instead, Grooms emphasized that BVD control requires several tools: biosecurity, diagnostic testing and vaccination. “If we effectively use the entire toolbox in a planned BVD control program, we can make great progress in controlling the disease not only in individual herds but across the entire industry,” he said.
– by Kindra Gordon
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