Trichomoniasis or “trich”
The first time I heard about trichomoniasis I believe I replied with a statement of trich…..what? It wasn’t long after that however that I started hearing more about this disease and the devastating results of finding it in your herd. Needless to say we started paying attention to trich, our first step was to contact our vet to discuss incorporating trich testing in our bull management program. Following are some of the things that I have learned about trich.
What is Trichomoniasis? Trich is a venereal disease of cattle that causes infertility and occasional abortions in cows and heifers. It is caused by Trichomonas fetus, a small motile protozoan found only in the reproductive tract of the bull and cow. Disease organisms transferred to the cow’s vagina from the bull during breeding migrate up to the uterus and cause the infection. The cow, after having been infected at breeding, may rarely show a very subtle, very mild vaginal discharge, 1-3 weeks later. Most of us would never notice it. The bull rarely shows any indication that he is infected. So, there are no outward signs that the bulls, cows, or heifers are infected with “Trich”.
What are the signs or symptoms of “Trich” in cattle? Neither the cow nor the bull appears ill at any time when they are infected with this organism.
What if Trichomoniasis gets into my herd? If it is a new infection (that is if your herd has never been infected before), you can expect a long, drawn-out calving season, with a disappointing total calf crop. In such herds, it is common to end up with a 50-70% calf crop, strung out over 3-8 months. If the herd has been infected for a long time, the effect may be slightly less. That is, a higher number of cows will get pregnant, but never as many as normally would calve if there is no “Trich” present. Because “Trich” often gets into a herd via the introduction of one infected animal, especially an infected bull, another scenario is possible. In this case, after the first year, the percentage of pregnant cows may fall from 95% to 90%, for example. In the second year, there may be further fall to 75% or less and a problem will be obvious. The reason for late or open cows is the fact that the Trichomoniasis organism causes the loss of the calf a few weeks into the pregnancy. A few cows in the herd (perhaps 5%) may actually abort due to “Trich”, nearly always before five months’ gestation. This disease can cause abortions, but most cows do not abort a fetus big enough to find. Instead, they come back into heat at some extended interval (usually more than 21 days) after breeding. Most cows will eventually settle if given enough time, but their immunity to the disease is weak. They can be reinfected the next season. What apparently happens when a “clean” cow is bred by an infected bull is that her egg is fertilized, but the disease organism either kills the embryo soon after conception, or the uterus’ reaction to the “Trich” organism kills the embryo.
How do I test for Trichomoniasis in my herd? Bulls are the long-term carriers of this infection where the T. foetus organism resides in the tissues lining the penis, prepuce and sheath. Since there is no treatment, all trich-positive bulls need to be culled to slaughter and replaced. A vaccine is available to help cows clean up faster from an infection and rebreed, but it doesn’t prevent trich from infecting the herd. If trich is found in even one bull, the entire battery needs to be tested. Trich can be diagnosed through the standard culture test or the newer PCR – polymerase chain reaction – assays which are a viable alternative to traditional culture techniques. PCR is a genetic test that actually looks for the DNA of the trich organism; therefore, it’s very specific. “It’s not fooled by other trichomonads that we really can’t tell apart in culture. Check with your vet to see which test he/she recommends.
How do I prevent my herd from becoming infected? A few simple management procedures (biosecurity protocols) can assist in reducing the possibility of a herd getting infected. Those procedures include:
1. Maintain a young bull battery.
2. Conduct a fertility exam and culture or PCR test all bulls before the breeding season.
3. Purchase only virgin, yearling bulls.
4. Do not share or lease bulls.
5. Do not purchase older cows and add them to your herd.
6. Cull open cows.
7. Maintain a defined breeding season to identify reproductive problems.
8. Pregnancy test all cows and heifers 120 days after the breeding season and cull open females.
9. Keep fences in good repair to keep your neighbor’s herd out.
10. You may elect to vaccinate, but vaccine alone will not prevent the disease from getting into the herd.
11. If you purchase an older bull verify that he has been tested and is clean of Trichomoniasis.
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