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Now is Time for Bovine Viral Diarrhea Testing

The NDSU Extension veterinarian is urging producers to get their cattle tested for bovine viral diarrhea.

An ideal time for producers to test their herd for bovine viral diarrhea may be just after calving and before turning cows and calves out on summer pastures, says North Dakota State University Extension Service veterinarian Charlie Stoltenow.

Bovine viral diarrhea (BVD) is, as the name implies, a viral disease and can infect cattle of any age. It is easily transmitted and highly infectious. It lowers production in the herd and affects the reproductive, respiratory, digestive and immune systems.

Clinical signs include pneumonia, abortions, stunted calves, weak calves, stillbirths, increased susceptibility to other diseases and, in severe cases, a watery diarrhea that frequently leads to death.

A peculiar ability of this disease is to produce persistently infected (PI) animals, Stoltenow says. If a pregnant cow is exposed to BVD early in gestation, the virus can become incorporated into the unborn fetus and the resulting calf will be persistently infected for life. These PI animals will serve as a reservoir for the BVD virus in the herd, continually exposing it to the disease. Even a good vaccination program will not protect the herd.

""Persistently infected animals can survive to become breeding cows and bulls in your operation,"" Stoltenow says. ""Another important point: A PI cow will always give birth to a PI calf."

Testing can be expensive, but new programs and techniques designed to minimize the cost are available, according to Neil Dyer, director of the NDSU Veterinary Diagnostic Laboratory.

""Not every animal on the ranch has to be tested, but every animal has to be accounted for, and every PI must be removed from the herd, preferably slaughtered, because we do not want to pass this disease on to our neighbor,"" Dyer says. ""Instead of testing all the cows, we test the calves. If a calf tests as a PI, we remove the calf and test the cow. If the cow tests as a PI, we remove the cow from the herd."

The available testing methods include techniques that can identify PI animals through ear notches and serum, molecular assays that can use serum, whole blood or ear notches, and traditional virus isolation from serum or whole blood.

The best time to test the herd is when the cows are open before the breeding season, Stoltenow says. He advises producers to consult their local veterinarian about what method is best for them and contact the Veterinary Diagnostic Laboratory about testing prices and timing.

""You can process a large number of animals quickly using these techniques, all with the goal of identifying PI animals and removing them as a source of disease for the rest of the herd,"" he says. ""Once PI animals are removed from your herd, you must commit to keep BVD out of your herd by testing any additions to your herd, including replacement heifers and bulls, and you must implement a BVD vaccination program."


Agriculture Communication

Source:Charlie Stoltenow, (701) 231-7522, charles.stolenow@ndsu.edu
Source:Neil Dyer, (701) 231-7521, neil.dyer@ndsu.edu
Editor:Ellen Crawford, (701) 231-5391, ellen.crawford@ndsu.edu
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