BVD could be eliminated with calf testing, vaccination
By CAROL RYAN DUMAS
JEROME, Idaho -- Bovine Viral Diarrhea is a costly disease in dairy and beef cattle, causing infertility, abortion, stillbirths, and early calf death, but not enough livestock producers are testing for the disease.
BVD is hard to manage, disguising itself through other ailments such as pneumonia, respiratory diseases and scours. The effects of the disease leads producers to blame cattle problems on other ailments instead of attacking the root of the problem, said Ron Kramer, sales manager of livestock and poultry diagnostics at IDEXX Laboratories.
In addition to reproductive problems, BVD suppresses the immune system, similar to AIDS in humans, leading to other viral and bacterial infections, Kramer told attendees to an AgSource herd health workshop in Jerome on Wednesday.
"It challenges overall herd health and producer viability," he said.
In dairy herds, BVD causes a decline in pregnancy rates, days in milk and milk production. In beef herds, it causes a 10 percent reduction in pregnancy rates and weaning rates, he said.
U.S. livestock losses to BVD were estimated to be $3 billion annually in 2008 and are likely to be quite a bit higher today. Tests cost less that $5, he said.
USDA estimates that 1 out of every 7 cow operations has a consistent problem with the disease. Prevalence of the disease runs 0.4 percent to 0.5 percent on beef feedlots and 2 percent on dairies, serving up losses of $20 to $80 per animal in the operation, he said.
The disease cannot be controlled with vaccination alone and is spread through persistently infected (PI) calves, born with the disease because their dams were infected between 30 and 150 days of gestation.
At that time of gestation, the virus crosses the placenta in infected cows, becoming part of the calf's DNA makeup, and it can't be vaccinated or doctored out of the calf, Kramer said.
The calf is a reservoir of the virus, shedding virus particles every day to every animal that comes in contact with it, he said.
Transiently infected (TI) animals, which clear the infection in 7 to 10 days, shed the virus as well but at a much lower rate. TI animals shed about 10,000 particles a day, whereas PI animals shed 10 million a day, he said.
"We could eliminate BVD if we tested every calf in the U.S. and put in a good vaccination program," he said.
PI calves look perfectly normal. The disease cannot be identified visually and has no geographic or breed boundaries. The only way to detect is through testing, he said.
Kramer recommends testing every calf, open cow and any new animal before adding it to the herd. Producers should also use tested bulls. More than 90 percent of PI calves come from PI negative cows.
A PI calf should be euthanized to prevent spread of the disease and a repeat of the cycle of cows producing more PI calves.
The disease causes no harm to humans and doesn't affect the safety of the meat of the animal. So an animal could be finished for slaughter, if it lives long enough -- PI calves usually die within the first two years of life. But it would have to be permanently quarantined with at least a 50 foot barrier from other animals, he said.
BVD calf-testing protocol
* Use a medium-size ear notcher.
* Prepare 3 clean vessels -- 2 with water, 1 with disinfectant (do not use an iodine-based disinfectant).
* Identify sample vials to the animal.
* Take a full notch from the calf's ear.
* Place notch in sample vial.
* After each use, dip notcher in water, disinfectant and other water container.
* Double check ID on vials.
* Refrigerate samples ASAP or ship immediately with cold packs to the lab.