What is Bovine Trichomoniasis?
I took this article off a friend's website to post on our website.
Gene Parker Jr. DVM, OSU Extension Area Food Animal Quality and Health Specialist
Recently the Nebraska Department of Agriculture has issued new requirements for the entry of Oklahoma breeding cattle into Nebraska. These requirements are meant to stop the entry of cattle infected with the organism Trichomonas. Because this disease has been relatively rare in Oklahoma, many producers in this state are unacquainted with it. The Oklahoma Animal Disease Diagnostic Laboratory has reported that several Oklahoma herds have been diagnosed with “Trich” in 2007.
Bovine trichomoniasis (commonly called “Trich”) can be an important cause of economic loss in cattle operations that use natural service. This disease is caused by a protozoan organism called Trichomonas foetus. This organism lives in the internal sheath and prepuce of the bull. In cows this organism colonizes in the internal reproductive tract.
How does it get transmitted? Trichomoniasis is a venereal disease of cattle. It is transmitted from cow to cow by a bull during breeding. Bulls show no clinical signs. Cows can commonly clear the infection within a few months; however, infection in bulls over 4 years of age is usually permanent and is the main source of transmission from one breeding season to another. The disease is self-limiting in cows, as opposed to bulls, that will be permanently infected. After several heat cycles, most cows and heifers clear the infection, but this may take months.
How does it affect cattle? What will you usually see if you have a problem? The most common signs in an infected herd are related to infertility. The cows will breed and settle, but then they experience early embryonic death of the fertilized embryo. About 30 to 40 days later the cow will once again come back into heat and breed. This may go on for 2 to 4 cycles until the cow clears the infection and settles for good, staying pregnant to deliver a full term live calf. While this whole process is happening the cows may have a calving date that is 3 to 6 months late.
Ranchers may notice the following signs when “Trich” infects a herd:
• Early abortion (too early to find an aborted fetus) and return to heat
• Repeated breeding resulting in long breeding seasons.
• A wide range of gestational ages at pregnancy check.
• In first-time infected herds, it is common to end with a 50 to 70 percent calf crop strung out over three to eight months.
How can you test your herd for infection? Visit with your local large animal veterinarian. Testing for Tritrichomonas foetus is usually done on breeding bulls by performing a preputial wash and inoculating the sample into special culture media. If one bull is found positive, you should assume that the whole herd is exposed.
Studies of positive bulls have shown that this culture method will miss about 10 to 20 percent of infected bulls if the test is performed only once. So, if no infected bull is found on the basis of one culture of all the bulls in the herd, then we can be 80 to 90 percent sure that the herd is "clean."
How can you treat infected herds? Again, it is important that producers visit with their veterinarian. There are vaccines available. The vaccines help cows/heifers to clear the infection in a matter of weeks (versus months in unvaccinated cows). In most cases, it does not prevent infection. The vaccine does not prevent infection or reduce the disease in bulls. There is no approved treatment for infected bulls.
How can you prevent the disease in your herd?
• Use young, fertile bulls or artificial insemination (AI).
• Culture new bulls at breeding soundness exam time.
• Keep a closed herd and test any animal that you buy.
How can you control the disease in our herd? If one of your bulls is positive for trichomoniasis, it is recommended to cull all bulls and vaccinate all females twice, one month apart. If you want to keep your bulls, you can vaccinate all females annually, but it would be better to cull all bulls and open cows before next season.
An alternative, if you don't want to cull all bulls, is to sample them at least three times at weekly intervals. With three negative tests, we will be 99 percent confident that a bull is negative.
[January 28th, 2008]
Dr. Rick Rasby, Professor of Animal Science
Animal Science, University of Nebraska - Lincoln, Lincoln, NE