Bovine Trichomonas
contributed article by Dr. Vince Collison, Collison Embryo and Veterinary Services,
Rockwell City, Iowa
Probably one of the most devastating causes of bovine infertility is an infection called Trichomonas foetus (Trich). This is a protozoan organism that infects the genital tract of both bulls and cows and is transmitted between cattle via sexual activity. Trich infection is spread primarily by an infected bull to a cow at the time of service. Once infected, a cow can be a source of infection to a noninfected bull when they mate.
There are no approved treatments for Trich and once a bull is infected, it will be infected for life. The reason for this is there are many crypts in the mucosal lining of the bull’s sheath. The protozoan that causes Trich will invade these crypts and makes the infection impossible to clear via natural immunity. If a cow becomes infected, they can clear the infection since their genital tract does not have these crypts on the mucosal lining of the vagina and uterus.
Trich Symptoms
Symptoms of Trich are only related to infertility. A bull or cow that is infected will not present any signs that will identify them as a Trich carrier. When a cow becomes infected after mating with an infected bull, it will take some time for the infection to colonize her genital tract. For that reason, a cow can and often will become pregnant after mating with an infected bull.
As the infection becomes more established in the cow, she will typically go on to abort the pregnancy at two to three months of gestation. A cow can clear the infection by four months after being infected provided there is no re-exposure. Therefore, cows can become rebred after losing an early pregnancy. This leads to cows having increased calving intervals and more calves being born late in the calving season. Herds that have been infected will also have more open cows and occasionally a cow with pyometra.
Significance of Preg Checks
This is one reason that it is important to pregnancy check cows. It is the earliest way to identify if there is a problem. Herds that have been infected by Trich will have more cows calving in the later part of the breeding window and experience more open cows than is normally acceptable. If an infected cow develops a pyometra (pus in the uterus), it will feel like a 75-to-100-day pregnancy but can easily be differentiated from a pregnancy with an ultrasound.
Biosecurity Measures
There are various biosecurity measures to prevent Trich infection from entering your herd. This would include:
1) Buying only virgin bulls. This is probably the best way of preventing Trich from entering your herd. Virgin bulls should have no exposure to Trich, and this information should be provided by the seller.
2) If you buy a nonvirgin bull, inquire if the seller has tested it for Trich and that the results are negative. Especially if the bull is coming from a part of the country where Trich is more common. If the bull has not been tested, request that the seller of the bull will have it tested before you take possession. As a precaution, it may be a good idea to retest the bull once it is in your possession and keep it in isolation until negative results can be confirmed.
3) Buy only cows or heifers that are four months pregnant or more. It takes that long for a female to clear the infection, so if they are at least four months pregnant they can be assumed to be free of Trich infection. This is why many states require a statement on a health certificate that females are four months or more pregnant when entering the state. There are rare occasions where a cow can become persistently infected and go on to deliver a live calf, but these cases are rare.
4) If your bull breeches the pasture fence and gets in with another herd or another bull enters your herd, it would be a good idea to Trich test your bulls at some point to ensure that Trich has not entered your herd.
5) Use semen for artificial insemination that has been collected from bulls tested free from Trich. This is one of the requirements for CSS certified semen.
Trich Testing
Testing for Trich requires collecting a sample from the sheath of a bull. Cows are not typically tested since they will clear the infection on their own by four months after exposure. The most commonly used test is the PCR test which is very sensitive. Samples can also be cultured instead but may need to be repeated two to three times to fully verify a bull is negative.
Regulatory Requirements
There are some regulatory aspects to Trich as well. Currently, it is not a federally regulated disease, but many states have their own requirements regarding Trich for movement. As the incidence and awareness of Trich has increased, more states have implemented regulations specific for their state. Since the individual state rules can change based on new policy, it is important to always check the state of destination if selling a bull out of state to be sure you’ll be in compliance with its entry requirements.
If you are buying a bull, it is the seller’s responsibility to meet the requirements for cattle entering your state. Some shows and consignment sales may also have their own rules on Trich which may exceed the requirements for their state.
Precautionary Measures
One aspect to consider is that if you are acquiring open cows for recipients, it would be best to let them sit for four months before using them, especially if they come from a part of the country where Trich is more common. This type of cow usually does not have any history and may have had bull exposure right up until the time of purchase. If they will be going to bulls after receiving embryos, this time frame of no sexual activity will greatly reduce the chance of a Trich infected cow entering the herd.
Work with your herd veterinarian to establish a good biosecurity plan to keep Trich from entering your herd or to help eliminate it if your herd is already infected. Your veterinarian will also work with you to make sure you have the proper testing done prior to moving cattle to another state. These regulations can vary from state to state, so give yourself an early enough start to allow enough time to get all of the proper testing done prior to movement.
learn more www.collisonembryoservices.com
Dr. Vince Collison is co-owner of Collison Embryo and Veterinary Services PAC
in Rockwell City, Iowa.
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