Quick to spread and impossible to cure – Bovine Viral Diarrhea (BVD) may be one of the most devastating economic hits cattle producers could face. And don’t let its name fool you, BVD wreaks much more havoc to reproduction in cattle than the digestive tract.
“Diarrhea is a very small part of the problem of BVD. Animals that are exposed to this virus have decreased immune systems so they are more susceptible to scours and pneumonia,” says Kansas State University College of Veterinary Medicine Dr. Gregg Hanzlicek. “For a cow-calf herd, the part of BVD that affects the herd the most is on the reproductive side.”
According to him, low conception rates, high risk of calf death within 40 days of birth, abortions at any point during gestation and multiple deformities in calves can be a result of BVD infection.
Calves exposed to the virus during gestation that make it to term will spread the virus all of their lives. These calves are referred to as persistently infected, or PI.
“A calf exposed to this virus 40-125 days of gestation takes it into its body,” says Hanzlicek. “The calf is born full of this virus and doesn’t recognize it (BVD) as being foreign, so it spreads it constantly from the time that it’s born till it dies.”
And it spreads easily.
According to Hanzlicek, all it takes is secretion from areas of the body such as the eyes or nose, including urine or feces to pass to another animal. To make things worse, BVD can survive for multiple days on inanimate objects such as boots and balling guns, making biosecurity practices essential.
It can also be spread during breeding, since the virus is transmitted through an infected bull’s semen. This also greatly decreases their fertility.
Here’s where it gets tricky.
“A PI animal that survives to breeding and has a calf will always give birth to a PI, but that’s only a small percentage of the PIs are formed,” says Hanzlicek. “Most PIs come from damns that are healthy that were just exposed to the virus during that stage of gestation.”
Because BVD will continue to circulate in a herd until PIs are found and eliminated, Hanzlicek recommends testing cattle. Once PIs are located, it is then up to the producer to do so ethically.
“These animals should not be sent to the sale barn,” he says.
According to him, by “passing off” a PI at a sale barn, fellow cattle producers are put at great risk of having their herds contaminated, whether it be from purchasing the PI or other cattle that have come into contact with it.