About 35 years ago, the buzz in cow country was the bull-of-the-year, as calf producers rounded up European and other “exotic” bloodlines to add to their herds. More recently, a chief concern has been the disease-of-the-year, as first one then another malady plagued the industry.

“Five years ago, trichomoniasis was virtually unknown to Missouri cattlemen,” said Dr. Craig Payne, veterinarian with the University of Missouri Extension’s Commercial Agriculture program. “Today, the disease is a likely culprit in cattle herds with low pregnancy rates.”

Trichomoniasis foetus (trich for short) is a venereal disease caused by a single-celled protozoan parasite and transmission of this organism during breeding can cut the calf crop by as much as 50 percent due to early embryonic death or abortion. The trich organism colonizes a cow’s reproductive tract (the inside of the penal sheath in bulls) and attacks the embryo that begins to develop after a cow is successfully bred. The cow typically aborts the damaged embryo and returns to heat.

“Other things can cause cows to fail to settle or to lose their calves early, but trich may be the culprit that often gets blamed on something else,” said Eldon Cole, University of Missouri extension livestock specialist. “If you have a high percentage of cows coming back into heat 50 to 60 days after breeding, suspect trich.
“This disease can be expensive because of strung-out calf crops, poor breeding rates and the cost of getting rid of trich once your herd has it,” Cole added.

The initial trich infection in cows usually does not interfere with conception but rather results in death of the embryo or abortion at 50 to 70 days of gestation, explained Dr. Payne. “As a result, cows and heifers typically return to estrus one to three months after breeding, but a period of infertility may last two to six months as a result of the infection.”

Cows and young bulls tend to “shed” the organism and clear themselves of the infection eventually. But bulls three years of age and older may become permanent carriers. “A small percentage of cows, though themselves still able to deliver normal calves, may become permanent carriers and spread the infection to other bulls in the following breeding season,” Dr. Payne said.
There’s currently no treatment to cure trich, nor a vaccine to prevent it. Individual animals—both bulls and females—show few or no obvious signs of infection. “The main symptoms of an infected herd appear as an excessive number of open cows—40 percent to 50 percent on average—and a calving interval prolonged over several months,” the veterinarian continued.

Fortunately, there is a new quick and accurate way to diagnose trich—usually made by testing the bulls. Modern tests using polymerase chain reaction (PCR) are more sensitive than traditional methods of culturing samples and looking for the trich organism under a microscope—which typically required three tests for a firm verdict.

“One PCR test can either clear or incriminate a bull,” said Eldon Cole. “I’d suggest always testing new bulls coming into the herd.”
How widespread is trich in Missouri herds? No one seems to have a good handle on that just yet.
“Between March and August, 2010, at least 18 Missouri counties were known to have herds infected with trich,” said Dr. Payne. “Most of those counties were in southwest Missouri—that’s where the largest concentration of beef cattle is—but no part of the state appears to be immune.”

“If we were testing bulls more extensively, we might be surprised at how widespread trich is,” guessed Cole.
“Testing for trich is not widespread yet,” said Dr. Mike Bloss, Countryside Animal Clinic at Aurora, Mo., who with several colleagues, conducts two bull breeding soundness clinics each year in spring and fall. “We offer to test for trich at these clinics, if owners request it, and several do. So far, the percentage of positive tests is pretty low. But we are seeing cows that don’t settle or those that return to heat after they’ve apparently been bred. Trich is one of the more likely suspects in these cases.”
Where trich is concerned, an ounce of “keep clean” is worth a ton of “clean up.” Prevention is the goal of animal health divisions in Missouri and several other states: they require a negative trich test on all non-virgin bulls being brought into the state. Oklahoma and Texas go a step further by requiring tests on bulls transferred within the state.

Preventing trich in your herd:
•    Isolate and test all new bulls.
•    When possible, buy only young, tested bulls and virgin heifers.
•    Consider using artificial insemination and manage for a defined breeding season.
•    Be wary of using leased or borrowed bulls, and keep fences in good repair. “A neighbor who lets you use his bull may not be doing you much of a favor if the bull carries in trich,” said Eldon Cole.
•    Keep accurate records.
•    Once your herd gets trich, management of the disease can be costly, involving culling infected bulls and open cows and replacing them with tested bulls and virgin heifers. But not managing trich can be even more costly, with open cows and strung-out calf crops.