Preventing and controlling trichomoniasis -

The disease is caused by the protozoa Tritrichomonas foetus, which lives in the dark, moist folds of the bull’s prepuce.

Bulls are typically unaffected and do not show clinical signs of infection, and therefore can serve as a reservoir of disease in the herd.

Older bulls are considered to be at higher risk of being chronic carriers because of a larger number of preputial folds and more chances over their lifetime to have been exposed to infected cows.

There are no effective, legal treatments for Trichomoniasis in the U.S., so control of this disease relies on testing and culling of positive bulls and preventing the introduction of disease into your herd.

Infected bulls spread Trich to cows during normal sexual activity. After exposure, the cow may experience a transient infection of the reproductive tract within one or two weeks, which usually goes unnoticed.

The cow may immediately cycle back or conceive in the face of infection; however, the embryo or young fetus will usually die by six to eight weeks after breeding because of the toxic and inflammatory effects of the organism.

After death, the inflammation will often lead to the formation of a pyometra (pus-filled uterus) and prevent the cow from cycling back and coming into heat.

Cows that become infected can transmit Trich back to naïve bulls while clearing the infection and thus may also spread the disease within the herd.

Most cows will clear the infection after a few weeks and develop short-lived immunity to Trich, lasting anywhere from six months to one year.

Cows can breed back and become pregnant at the end of the breeding season, although less than 1 percent of these cows may remain infected throughout pregnancy and serve as a source of disease the following year.

Working with your veterinarian, you should suspect Trich if you have an unusually low pregnancy rate, many of the pregnancies are from the end of the breeding season (younger pregnancies at pregnancy check), or if there are multiple pyometras detected at the time of preg check.

Testing
Bulls should be tested for Trich anytime they are sold, loaned or leased, and as part of a routine breeding soundness exam prior to turn-in with cows.

Some states will require all positive bulls to be reported to the state veterinarian as part of control and eradication efforts. Positive bulls should be sold for slaughter only.

The most common sampling technique in bulls is a dry preputial scraping to obtain a smegma sample from high up in the prepuce.

Bulls should be sexually rested for at least 10 days prior to being tested by your veterinarian and not re-introduced to cows until negative results are available.

Proper sample handling is critical to an accurate test result, so the sample is placed into specific transport media and submitted to an approved laboratory that will run one of two tests:

1. Culture – The sample will be incubated and examined under the microscope for Tritrichomonas foetus. If no organisms are seen after five days, the test is considered negative.

To consider a bull truly negative, they should have three negative cultures, taken one week apart, as the confidence in a negative result increases with each sequential test.

2. Polymerase chain reaction (PCR) – The sample is incubated for 24 hours and then is tested for DNA specific to Tritrichomonas.

This is a much more rapid test and helps to differentiate Tritrichomonas from other benign trichomonads that may be found in the environment and appear similar.

Most states will accept a one-time negative PCR test as adequate to classify a bull as negative.

Prevention and control
Preventing Trich from entering your herd is essential to maintaining a healthy bull battery. Here are a few basic recommendations for reducing the risk of introducing Trich into your herd:

If you are not raising your own replacement animals, purchase virgin bulls and heifers from a known-negative herd.
All new bulls should be tested for Trich before being introduced into the rest of the herd.
Know the status of cows and bulls with which you are sharing grazing lands. Many grazing associations already require annual Trich testing.
Try to maintain a shorter breeding season (60 to 90 days). If open cows are culled after a short breeding season, it both selects for cows breeding early in the year and reduces the chances of diseased animals going undetected. A longer breeding season may allow infected animals to breed back and maintain Trich in the herd.
Consider using artificial insemination to reduce the risk of exposure to cows and heifers.
There is one commercially available killed Tritrichomonas vaccine in the U.S. (TrichGuard by Boehringer Ingelheim).

Vaccination of cows is a valuable tool in an infected herd and will help increase pregnancy rates; however, it does not appear to protect bulls from the disease nor does it cure bulls of the disease.

Vaccination must be repeated annually and should not be considered a substitute for routine testing and culling of positive animals.