Trichomoniasis, a new challenge for producers
After many years of testing and culling, Oklahoma regulatory veterinarians, practitioners, and cow/calf producers have succeeded in pretty much eliminating brucellosis as a threat to reproductive efficiency. Unfortunately, “just when you thought it was safe to go back in the water,” a new challenge has appeared on the scene. Trichomoniasis is not a new disease, but its prevalence has increased dramatically in recent years, mostly due to the increased movement of breeding stock from region to region. Commonly called Trich, it is a highly contagious venereal disease that causes infertility and abortions.
Trich is caused by the protozoan pathogen Tritrichomonas foetus, which can live in the cow’s reproductive tract and on the surface of the bull’s penis. This organism has a close cousin, Tritrichomonas intestinalis, which lives in the intestinal tract and causes no problems. It may, however, be picked up in testing, causing a false positive, if fecal material splashes onto the penis.
There are no apparent signs of sickness in animals infected with Tritrichomonas foetus, but the herd will have too many open cows, abortions, extended calving season, and in a few cases, uterine infections. The bull serves as a mechanical vector to spread the disease within the herd. In some younger bulls, the infection may clear itself in time if the bull is not reinfected by breeding more infected cows. In older bulls, the microscopic crypts in the prepuce, or sheath, become deeper and the organism establishes itself deep within these crypts, resulting in chronic infections. Most bulls aged 4 years or older, and some 2- and 3-year-old bulls, develop chronic infections which cannot be cleared. Slaughter is the only viable alternative for these bulls. Cows are infected at breeding. Eighty percent to 90 percent of the cows served by an infected bull will become infected. After failing to establish a pregnancy for several cycles, the cow can develop a temporary immunity and maintain a successful pregnancy to term. This results in an extended calving season if the bull is left on the cows with resulting small light calves at weaning. If the bull is put with the cows for a limited breeding season, the results will be a poor pregnancy rate and too many open cows. This immunity is short lived, however, and the cow is susceptible to another course of the disease in the following year. Some herds, in fact, experience relatively mild problems in the first year but have a real reproductive calamity in the second year. Trich is diagnosed in the bull by testing at least two weeks after he has done any breeding. The veterinarian washes material from the penis and sheath of the bull for the lab to culture in order to see if the organism is present. It takes from five to seven days to run the test. Unfortunately, one test does not al ways
tell the true story. If you have multiple bulls, one test on all the bulls may serve as a screening tool to determine if the disease is in your herd. For regulatory issues such as bulls going out of state, most states will require three consecutive negative cultures. An alternative is the PCR test. Although this test is more expensive, reliable and acceptable results can be obtained with one test. The PCR test also has the ability to differentiate between the pathogenic Tritrichomonas foetus, and the incidental contaminant Tritrichomonas intestinalis. If cows are to be tested, the test is run on vaginal mucous 10 to 30 days post breeding. In the cow, five negative cultures are required to say conclusively that she is not infected.
Prevention of trichomoniasis requires a multilevel approach. The first step is to test the bulls in your herd and slaughter the positive animals. Using young bulls will help to prevent chronic infections. When you acquire new bulls, buy virgin bulls from reliable sources. If new additions are not virgins, or if their past breeding status is unknown, test them with the PCR test. The incidence in cows can be reduced by using a short breeding season and culling open cows. There is a lot of wisdom in the old saying that “good fences make good neighbors.” Prevent comingling with neighboring herds to prevent passing this and other venereal diseases back and forth. A vaccine is now available for prevention. Two vaccinations are required to start the program.
These vaccinations should be given four weeks apart and concluded four weeks before breeding season. Subsequent single annual boosters are required. While this will help to minimize losses when used in the cows, it will not clear chronically infected bulls or prevent bulls from becoming infected if they breed an infected cow.
Currently, all of the states surrounding Oklahoma have regulations for breeding bulls moving into those states. While regulations differ from state to state, they all require testing unless the bulls are going to slaughter. Some states allow virgin bulls to enter if accompanied by a veterinarian’s certification. Oklahoma requires testing on all bulls entering the state except for virgin bulls under 24 months, cutting bulls bound for feedlots, slaughter bulls, and rodeo bulls entering for an event other than transfer of ownership or breeding purposes. No one knows how widespread the problem is in Oklahoma, but there are producers who have had to slaughter large numbers of breeding bulls. Most producers are supporting proposed regulations which have been prepared by the Oklahoma Department of Agriculture and are being considered by the state legislature this session. These regulations would better define entry requirements for out of state bulls and require testing for bulls being sold for breeding purposes either at auction or private treaty within the state. Cows from infected herds would be restricted from entry into the state. These regulations also include a provision for Oklahoma seedstock producers to participate in a voluntary herd certification program.
Your local veterinarian is your best source for more information. He will be able to help you assess the risk factors in your area and within your herd, and suggest appropriate prevention steps that fit your operation effectively and economically. He will also know where to go for current answers to the continually changing regulatory questions for both Oklahoma and neighboring states. — Dave Sparks, DVM, OSU Area Extension Quality and Health Specialist