Ten years after bovine trichomoniasis was found in Western Canada, the venereal disease remains a threat to cattle producers.
Hiding in the folds of penis skin and in the preputial cavity of bulls, the disease has pushed cattle producers to watch every entry point for infection in their herds and even consider closing access entirely.
Trichomoniasis reduces pregnancy rates by 20-60 percent and can result in culling otherwise healthy cows and disposing of valuable bulls.
With most producers relying on communal grazing for part of their production cycle, they are forced to consider not only the disease status of their animals but also those of their neighbours.
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Community pastures generally refuse open cows or cows without calves at their sides to help prevent venereal disease transmission, but some cows successfully carry healthy calves to term while maintaining a mild trichomoniasis infection. These animals can become carriers and infect community pasture herd bulls, which in turn pass the protozoa among the communal herd.
Christoph Weder of Alberta Agriculture said producers “need to remain vigilant about this disease. Nobody needs lower production numbers, especially this year.”
Because bulls are asymptomatic, they must be tested through a herd-screening program. The preputial cavity is scraped or flushed and the samples, mixed with a growth medium, are sent to a laboratory for analysis.
In cows, samples are taken from the vagina or uterus, but these tests can miss some cases.
The infection causes cows to develop uterine swelling that eventually results in abortion.
“For that reason, calf fetuses need to be tested,” said Al Barth, a reproduction scientist with the University of Saskatchewan’s Western College of Veterinary Medicine in Saskatoon.
“With this disease, it can be one of the only ways to catch it.”
Barth said producers holding unbred cull cows need to ensure they are not exposing them to bulls intended for anything other than slaughter.
“All open cows should be treated as suspect, just in case,” he said.
“Every year we get a few unexpected flareups and then it means a pretty extensive cull. Tests are only good for about nine out of 10 bulls so even if the community pasture is testing, this is becoming a real production issue.”
Animal agrologists and researchers agree herd management is the only way to control the disease.
Virgin bulls must be kept away from cows, especially those that may have had problem pregnancies or are open unexpectedly later in the season.
Barth said most communal pastures have created management systems that keep virgin heifers and cows with calves in smaller groups, each with an assigned bull that is not allowed to mingle with other groups.
Bulls should be tested weekly for three weeks to ensure that low levels of the parasite are not missed. Bulls once infected are considered carriers.
“Leasing or loaning bulls isn’t a good idea unless a lot of precautions are taken,” Weder said. “It’s best to talk to a vet about that.”
Barth said attempts are being made in some American states to manage the disease with vaccinations, but he said the vaccine isn’t considered reliable.
“The less one producers’ herd meets another one, the fewer problems there will be,” he said.
