Vet´s perspective

News
Dec 9, 2011
by WLJ

Tritrichomonas: a silent infection

A fairly common infectious disease, tritrichomonas foetus is a protozoan that can wreak havoc on the reproductive capacity in your herd.

The microorganism is slightly larger than a red blood cell and resides on the surface skin within the penile sheath. Spread of disease is most often via coital contact. Bulls are affected after breeding with other infected cows— and often develop a carrier state without demonstrating clinical signs of illness. Cows on the other hand, unfortunately suffer the consequences of disease.

Economic losses related to this infective organism result from the costs associated with treatment, culling and replacement of cattle, reduced calf crops, and lower calf birth weights. Past data demonstrated approximately a 20 percent reduction in calving rate and an average of 40 days in delay of conception rate among infected herds versus those without disease prevalent.

Typically, the first signs of disease are noticed when herd cows begin demonstrating recurrent abortions and difficulty conceiving. The disease has been diagnosed to date as more or less endemic within every state.

Cows are infected during copulation with infected stud bulls as well as contaminated insemination equipment. The infection produces a mucoid discharge from the vulva within a few weeks of breeding, and results in vaginitis, cervicitis, endometritis and placentitis.

A “red flag” of illness is detected at pregnancy checks—when several cows are found to be open with (sometimes) an associated pyometra, or pus-filled uterus. The rate of infection de pends upon the number of organisms present at time of inoculation as well as the immune system of the animal. Often, a rapid growth occurs, and death of the developing fetus happens before day 80 of gestation.

Using a routine method during collection is essential for accurate results. Your veterinarian will flush the prepuce lining with sterile water prior to collection of a preputial scraping. The scraping pipette should be handled carefully to prevent touching the outside of the sheath during collection, as well as using sterile technique when inoculating samples into the collection media.

The T. foetus organism cannot live long in the environment outside of the body.

This fact may also impact collection—as the process must occur rapidly and the environmental temperature can be neither too cold nor too warm for inoculation to take place. As the organism dies off, it produces an enzyme that breaks down the DNA of fellow protozoans, which may lead to a false negative result as well. In- Pouches containing samples must stay frozen until delivery to the assigned laboratory in order to insure adequate analysis.

Testing for the infectious organism tends to occur along with breeding soundness examinations on herd bulls. The ‘InPouch’ collection pouch acts as a media source for T. foetus and allows for recovery of the organism upon rapid transport to a designated laboratory for analysis. As with any culture media source, samples may be easily contaminated by other bacteria present in the environment, so proper handling of all collections should be carried out with routine protocol on behalf of your veterinarian. Re-testing problematic bulls may be indicated as heavy bacterial and fungal growth in a contaminated sample can outgrow T. foetus and result in false negative findings.

Laboratories may detect the organism via three consecutive cultures or via PCR—a method that detects the trichomonas DNA with a single test. PCR testing is a much faster route for attaining results. History of infected herds typically involves new additions to a farm that have not been adequately tested for disease and appropriately quarantined from herd mates. Use caution when purchasing replacement cows and invest in breeding soundness examinations with preputial cultures on ALL new stud bulls to your facility.

The advent of antibiotictreated semen during artificial insemination as well as intensive screening of bull studs has significantly helped with decreasing the amount of positive results; however, this is no reason to take a lax attitude in preventative care for your herd. The increased prevalence in western states may be related to an actual high risk of disease and the enhanced ability to more accurately diagnose the disease.

Prevention of venereal disease is limited to sexual contact and contact from mechanical carriers associated with breeding acts. Measures that can help prevent illness include: avoiding common grazing between pastures with unknown disease status, utilizing bulls that have been tested for infective T. foetus, recording breeding seasons in order to detect early delays in conception and abortions, utilizing artificial insemination programs when feasible, and including tritrichomonas and campylobacter vaccinations in prebreeding programs when appropriately advised by your veterinarian.

Control disease in a diagnosed herd by identifying and eliminating chronic sources of infection. Allow for a minimum of three weeks of sexual rest for all breeding bulls before collecting culture samples from the prepuce. This may allow for opportunity of spontaneous recovery to occur and potentially reduce the likelihood of falsenegative results in chronically-affected animals. Using a set breeding season of two to three months enhances the ability to keep a tighter outlook on which animals are bred and open—versus a year long season in which records are more difficult to attain. Cows can develop short term immunity and often are treated symptomatically. Judicial use of culling rates in affected cows may be needed as the bottom line depends on the amount of time you can afford to feed an open cow.

Contact your veterinarian or university extension agent regarding venereal disease testing rules and regulations for your area. Many veterinarians will retrieve preputial samples during standard breeding soundness examinations. Also, routine testing is often required when bulls are sold and traveling, especially between county and state borders. — Dr. Genevieve Grammer [Dr. Genevieve Grammer is a mixed-species veterinarian practicing in eastern Colorado. Please direct correspondence to drgigi19@ gmail.com].

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