- Category: Animal Health
- Published: Tuesday, 23 July 2013 18:06
- Written by Anne Johnson
- Hits: 27462
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In response to requests from the Utah Cattleman's Association and Utah Farm Bureau, Utah animal health regulations now require all resident bulls over nine months of age and bulls entering Utah, to be tested negative for trichomoniasis. This testing is to be done by an accredited veterinarian. All bulls tested will be tagged with a current Official State of Utah Trichomoniasis test tag to allow for permanent identification. Any bulls testing positive are prohibited from sale as breeding animals and must go to slaughter within 10 days. Any bulls purchased for breeding purposes must be tested negative for trichomoniasis prior to change of ownership and before exposure to any cows.
What is Trichomoniasis?
Trichomoniasis is a venereally transmitted disease of cattle which results in varying degrees of reproductive inefficiency (usually early embryonic death). Since it causes no alarming clinical signs, it often goes undetected for long periods. The trichomonad is a protozoan that lives in the crypts (wrinkles or folds) on the mucosal surface of the penis and prepuce of the bull. These organisms are transmitted to the cow by breeding. At breeding the sperm fertilizes the ovum, and the embryo begins its development. After a few days, this embryo attaches to the uterine wall where the circulation necessary for its nourishment and growth begins to develop. If the cow was exposed to trichomonads at the time of breeding, these tiny protozoa grow and multiply on the lining of the uterus, causing an inflammation (metritis) which eventually disrupts the placental circulation supplying nutrients to the new embryo. Death of the embryo follows. This usually takes place within the first 30-60 days of pregnancy. The cow then expels (or absorbs) the dead embryo which is very small and typically goes undetected. The only clinical manifestation may be a uterine infection with minimal vaginal discharge. The cow's immune system usually responds to the trichomonads and eliminates them from the reproductive tract. This takes place in 90-100 days with the return of the estrus cycles of the female. Then the cow can breed back and carry the new fetus to term (late calver). Although infection does stimulate immunity, it is not durable and the cow may be fully susceptible by the next breeding season. In rare cases, a cow can calve normally and remain a carrier. A number are rendered infertile, with some developing an accumulation of pus in the reproductive tract (Pyometra). This manifests as an unusually high number of open cows and a few with bad uteruses at pregnancy checking time. The infection in the bull is completely without clinical signs. The crypts or folds in the mucous lining of the penis and prepuce provide the necessary environment for replication of the trichomonads. As a bull matures these crypts become more pronounced, providing a more suitable environment for the trichomonads. While the trichomonads grow in these crypts, they do not stimulate the bull's immune system, thus the bull remains infected. Bulls may become infected by breeding a cow which was just bred by an infected bull or by breeding a cow which has trichomonal metritis. The most infective time is during this metritis phase since there are billions of organisms present in the vaginal discharge.
When should you suspect trich?
Trichomoniasis is not the only cause of reproductive inefficiency or failure. Whenever a high number of cows are cycling toward what should be the end of the breeding season, or are found to be open in the fall, trichomoniasis should be considered as one of several possible causes. Other possibilities, such as Campylobacteriosis (Vibrio), nutritional problems, or simply infertile bulls should also be considered. Your local veterinarian should be contacted as soon as possible when you detect such problems in your herd, since he is the most likely to be acquainted with your operation and problems in the area.
It is best to prevent entry of this disease into the herd. For some producers this is simple: buy only virgin bulls or heifers for replacements, have the bulls tested, and do not commingle your herd with any other cattle. If you participate in a grazing association or run on the forest or BLM with other operators, it is helpful to have the majority of your cows pregnant before going onto common ranges, thus decreasing the chance of transmission. If the breeding program is to be carried out on a common range, then it is essential that only clean bulls be allowed. A good way to assure clean bulls is to stock with virgin yearlings. All the bulls should be tested negative to insure that they are clean.
Vaccines for trichomoniasis have been produced by biological companies and are available for use. They are of benefit but will not prevent it from infecting a herd if an infected animal is introduced. Vaccination is of special benefit and help where the owner is not able to maintain animals in complete isolation. When using the vaccine, be sure to follow the directions carefully. Two doses are required the first year and there will be very little protective immunity until after the second vaccination is given. A single annual booster is required in each following year.
What if you already have trich in your herd? You should meet with your veterinarian to discuss the following (and other) measures for controlling the disease after it has become established in a herd or grazing association:
- Check all cows for pregnancy at the end of the breeding season and cull all open cows at that time.
- Cull all older bulls (three years and older) to slaughter.
- Have all remaining bulls sampled for trich at least three times before the next breeding season. The multiple testing greatly increases the opportunity to find infected bulls.
- Buy only virgin bulls for replacements.
- Make sure that all members of the grazing association adhere to these guidelines.
- If practical, divide your herd into smaller units for breeding. (Or consider the feasibility of using artificial insemination.)
Should you have other questions about specific details or other control measures which might be available, please contact your veterinarian, the Utah Department of Agriculture and Food or ask your local extension agent to arrange an educational program in your area dealing with the problem of trichomoniasis.