Trichomoniasis or “trich” for short is a venereal disease of cattle that causes infertility, open cows, and abortions in cows and heifers. It is caused by Tritrichomonas fetus, a small protozoan parasite of the reproductive tract of the bull and cow. Trich is transmitted to cows by sexual contact with an infected bull. In the bull, the microbe lives in the folds of skin that line the penis and internal sheath; in the cow or heifer the organism lives in the vagina, uterus, and oviducts.

Infected cows or bulls show no outward signs of infection. Typically, the first time a herd becomes infected with trich the calving season may be long and result in fewer calves. Sometimes the disease is not suspected the first year of infection because pregnancy rates might only drop a small amount (e.g. from 95 to 90%). However, by the second year it is usually clear that there is a problem because reproductive losses become greater. Having trichomoniasis in a herd is very costly.

Trichomoniasis is a self-limiting infection in cows and heifers. They usually eliminate the infection within 6 months. However, immunity is short-lived and cows may become re-infected. Unlike the cow, bulls do not clear the infection. Once a bull is infected he may carry the disease for years and serve as on ongoing source of exposure to the herd. Older bulls are more likely to become infected and to stay infected.

Trich is diagnosed by testing bulls. Testing for trich involves taking scrapings of preputial (internal sheath) fluids. This should be done by a veterinarian because collection and sample handling effect the reliability of the test. Repeating this test up to 3 times at 1-2 weeks intervals increases the probability of detecting the infection. Current diagnostic methods will detect 80-90% of infected bulls with a single test. If even one bull is positive, you have to assume that the herd has been exposed.

Trich is a complex problem and your veterinarian should always be consulted regarding decisions about diagnosing, preventing, or controlling, this disease. It is easier to prevent the infection than to try to control or eliminate it after it enters the herd.