REGINA — The best way to eliminate bovine trichomoniasis from a herd is to get rid of infected animals, says an American veterinarian.
Producers should be testing for the reproductive disease, said Mike Thomas, of California State University at Fresno. Speaking at a recent Saskatchewan Livestock Centre field day he said a mandatory testing program in Idaho determined about five percent of all bulls were infected. About 10 percent of all herds had at least one infected bull.
“Where you accurately test for it, you’re going to find it,” Thomas said. “I suspect you’ve had it up here (in Canada) for a while.”
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Trichomoniasis is caused by a tiny organism that lives in the reproductive tract. It is transmitted from bull to cow during breeding, but there are no outward signs of infection.
The disease can cause early embryonic death, abortion, infertility or a uterine infection. But sometimes a cow can carry a calf to term even while being infected, Thomas said.
The economic effect of trichomoniasis could be enormous, he said. Up to half of a calf crop could be lost, although more typical losses are between 10 and 20 percent.
“One infected bull out of five in a herd of 200 cows could reduce the pregnancy rate from 96 to 82 percent,” Thomas said.
Older bulls are more likely than younger ones to become long-term, permanent carriers, but even so-called virgin bulls as young as eight months old have tested positive.
Carrier through pregnancy
Cows are usually free of the disease within three to five heat cycles after losing a pregnancy. However, Thomas said some cows will carry the organism through pregnancy and the post-partum period. These carrier animals pose a significant problem to disease control because testing now focuses on bulls.
There is no treatment, although there is a vaccine that has had limited success in cows. Thomas said control must centre on keeping cows from infected bulls, and keeping bulls from breeding infected cows.
Control measures include limiting exposure to bulls to 90 days, replacing old bulls with younger ones, testing all new bulls coming into the herd regardless of age, testing bulls before the breeding season and again two weeks afterward, culling open cows at pregnancy check time, vaccinating cows, using artificial insemination if practical and controlling other reproductive diseases in order to make it easier to identify trichomoniasis.
