Trichomoniasis in Cattle:
Could it be coming to a herd near you?
For herds experiencing low pregnancy rates, a venereal disease called trichomoniasis, or trich, may be a likely culprit, University of Missouri (MU) Extension Veterinarian Craig Payne told Missouri cattle producers at a Sept. 16 beef field day at MU South Farm, Columbia.
Trich is caused by a protozoan parasite called Tritrichomonas foetus. Transmission of this organism during breeding can reduce the calf crop by as much as 50% due to early embryonic death or abortion, Payne said. "This disease can have a devastating financial impact because of poor calf crops and expenses associated with cleaning up an infected herd."
Between March and August of this year, at least 18 Missouri counties were known to have cattle herds infected with trich. Most of those counties were in southwest Missouri, but no part of the state appears to be immune.
"The initial infection in the cow usually does not interfere with conception but rather results in death of the embryo or abortion at 50 to 70 days of gestation, on average," Payne said. "As a result, cows and heifers typically return to estrus one to three months after breeding, but a period of infertility may last for two to six months as a result of the infection."
Cows and some young bulls tend to clear themselves of the infection eventually, but bulls 3 years and older tend to become permanent carriers. A small percentage of cows, though still able to deliver normal calves, may become permanent carriers and spread the infection to other bulls in the following breeding season.
There's no treatment for trich, and individual animals show little or no obvious clinical signs of infection, Payne said. "Symptoms of an infected herd appear as an excessive number of open cows — 40%-50% on average — and/or a calving interval prolonged over several months."
Diagnosis is usually made by testing the bulls. If you suspect trich, have a veterinarian collect samples and make a diagnosis. Modern tests using PCR (polymerase chain reaction) are far more sensitive than the traditional method of culturing samples and looking for the trich organism under a microscope. "A bull can be declared trich-free with one negative PCR test, whereas the culture method requires three negative tests," he said. Management of the disease involves culling infected bulls and open cows and replacing them with young, tested bulls and/or virgin heifers.
Editor's Note: For more about this disease, see "Trich: Not Just a Western States Disease" in the October 2010 Angus Beef Bulletin.
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