Bovine viral diarrhea virus (BVDV) continues to be a vexing problem for cow/calf producers. BVDV is spread in multiple ways, and the risk control effort needs a multipronged approach, according to a Zoetis announcement.
According to Dr. Paul Walz, professor of pathology at Auburn University, there are three steps to controlling BVDV infections:
- Immunization, and
Vaccinating is the act of giving the animal a vaccine, Walz explained, while immunization is when the animal has an immune response to the vaccine. He said producers ideally will give two doses of modified-live virus (MLV) reproductive vaccine in replacement heifers before they are bred for the first time, with the last dose given approximately 30 days prior to breeding.
Annual re-vaccination with an MLV vaccine gives effective protection against BVDV infections, Zoetis said, noting that if the MLV program in the mature cow herd doesn’t work for a particular operation, a killed BVDV reproductive vaccine at pregnancy check time can also provide protection for the herd against BVDV infection.
Once producers have established a strong vaccination protocol for the cow herd, it is time to look beyond immunization to apply additional tools and management to reduce BVDV risks, Zoetis said.
A cow persistently infected (PI) with BVDV will always have a calf that is PI with BVDV. Walz pointed out that the PI calf is a central figure in how BVDV maintains itself within a herd and how BVDV travels from herd to herd. However, the risk for spreading BVDV extends throughout an operation, to equipment, visitors to the farm and fence-line contact among animals.
With so many avenues of BVDV transmission, the work to control the risk begins with biosecurity, he added.
“We cannot rely on immunization to 100% prevent PI infections, nor can we look at our diagnostic test to pick up every single PI animal, so biosecurity is a really good way to reduce risk,” Walz said.
The main path for BVDV introduction to a herd is through new cattle. The “Trojan dam” — a highly immune cow that is a PI carrier in its reproductive tract and uterus — makes detection difficult, Walz explained. The cow would pass any test for BVDV, but it is, nonetheless, an infected animal. Producers who purchase pregnant animals or are bringing them back from a heifer raiser must contain them for biosecurity purposes to reduce BVDV spread.
“If at all possible, test for PI status of the newborn calves on the new cows rather than allowing those cows to calve within the general population of cows,” Walz said.
Walz shared some other essential components of effective biosecurity measures, including:
- Avoid bringing in new animals unless they’ve been tested.
- Isolate sick animals from healthy ones.
- Move dead animals away from the barn.
- Pay special attention to young animals.
- Practice general hygiene — soap, water and general disinfection.
- Monitor visitors, and be aware of how they can transmit BVDV from farm to farm.
Taking time to test
“We have excellent tests available for BVDV,” Walz said. “We have better tests for BVDV than we have for a lot of our other diseases, including infectious bovine rhinotracheitis.”
Walz said testing the newborn calf is essentially testing the dam, and knowing those results can set in motion biosecurity measures and other steps. There are numerous ways to test, and working with a diagnostic laboratory can help produce the most useful results, he added.
“Your diagnostic lab is a tremendous resource for testing but also a tremendous resource for information on how to test and when to test,” Walz said.