Tritrichomonas foetus is a venereally transmitted protozoan that infects the reproductive system of cattle and is the causative agent in bovine trichomoniasis. The disease can be devastating to a herd – early embryonic death, abortions, prolonged calving seasons and open cows at pregnancy check. The protozoan is 20 µm x 10 µm, pyriform in shape and contains a single nucleus, an undulating membrane, and three flagella that extend from the anterior end with one off the posterior end. Tritrichomonas foetus is present in the United States with most cases being in western states where cattle are co-grazed on large rangeland. More than fifteen states have established regulations for testing and control.

Recognition of a T. foetus infection is difficult because there are usually no obvious clinical signs. In the bull, the protozoan will live in the folds of the prepuce and distal portions of the penis and urethra (Rae, 2006). As this is more of an external infection, no immune reaction occurs nor are there any pathologic lesions in the bull. As the bull ages, folds in the prepuce of the bull increase in size, and deep crypts are formed. These crypts allow for T. foetus to establish a chronic infection and create a carrier state. The carrier state usually does not develop in bulls until they are three to four years of age, the time at which the crypts deepen (Peter, 1997). Disease in the cow results from exposure to the organism during mating with the bull. The organism proliferates and infects the uterus, cervix, and vagina. Mild vaginal discharge may be noted by a watchful herdsman. Pyometra develops in 5% of cases (Kimsey, 1986). The infection can cause an endometritis and/or placentitis that will affect embryonic attachment to the uterus and fetal development. If pregnancy was established, fetal death usually happens at 50-70 days of gestation (Rae, 2006). Depending on the course of disease (early embryonic death or abortion), the cow will return to estrus after a prolonged period of time. Most cows are able to establish an immune response and clear infection in 90 days (Peter, 1997). The immune response creates a short lived protective immunity that prevents reinfection later in the breeding season. A carrier situation has been noted in females and is rare (Skirrow, 1987). These cows can be responsible for carrying the infection into the next breeding season and infecting new bulls.

Testing for Tritrichomonas foetus is available, but it takes a knowledgeable veterinarian to pick up the changes in breeding records for a herd. Signs to watch for include: low pregnancy rate, mostly late breeding season pregnancies, a gap in gestational lengths with few cows pregnant from early in the breeding season and the remainder pregnant from late in the season, and cows with pyometra detected at pregnancy check that was not present after calving. Breeding records can vary with each situation and pastures with multiple bulls can compound the diversity of the clinical picture further. Routine testing of bulls is the best practice to prevent infection and economic loss in the herd.

Samples taken for testing a bull are smegma or epithelial scrapings from the prepuce. In the female, vaginal or uterine fluid is aspirated. All samples should be collected aseptically to prevent contamination of the sample and introduction of a secondary infection in the animal. A wet mount of the samples can be examined under the microscope, but this has low sensitivity (30%)(Peter, 1997). Other protozoa may be present in the prepuce and lead to misdiagnosis, but there is also the risk of not detecting the organism if T. foetus organisms are rare in the sample. Serial culture sampling is the gold standard for diagnosis of trichomoniasis. Several media are available, but the commercial product InPouch™ TF has become popular. The container is a clear plastic pouch that allows for direct microscopic examination through the plastic, and no slide preparation needed. The media, a modified Diamond’s medium, is already in the pouch and has a shelf life of a year. The InPouch™ TF is produced by BioMed Diagnostics in Oregon, and ordering is available on their website. Sensitivity of the commercial product is the same as other culture media (Parker, 2003). Sensitivity of the culture method is reported to be 81-95% (Rae, 2006). The test is not 100% specific either, and a false positive diagnosis may be made when a gastrointestinal flagellate is present in the culture media. Polymerase chain reaction (PCR) is improving and providing a useful tool for diagnosis of T.foetus. Primers are changing and allowing for differentiation of T.foetus from other trichomonads. In 2007, Cabo et al. worked on determining the sensitivity and specificity of culture (InPouch™ TF) and PCR in parallel and serial trials from bull smegma samples collected for six weeks. The results of their investigation are summarized in the chart below (Cobo, 2007).

For an accurate diagnosis, a bull needs to be sampled and tested multiple times. Culture has been the gold standard for many years, and with the addition of two-step testing (positive culture followed by PCR), bulls can be diagnosed with a protozoan being present and then tested with PCR to determine if it is T. foetus. More than 15 states have adopted regulations for trichomoniasis and testing bulls. Each state has individual guidelines and testing requirements. Virgin bulls are exempt from testing as long as it can be proven that they have not been permitted to have cow exposure. If an abortion occurs, fetal tissues can be examined to determine if T. foetus was the cause. The organism can be visualized microscopically in the placenta, lung and abomasal fluids most readily.

Treatment is not available for T. foetus. Available vaccine does not prevent infection but decreases the infection time in the female. No efficacy with the vaccine is noted in bulls. Prevention is key. Some herd preventative practices include:

• Use only virgin bulls
• Test all new bulls prior to adding to the herd
• Test bulls annually to ensure the bulls have not become infected
• Do not buy cull animals or animals that do not have a well documented history
• Do not co-mingle with other herds on large ranges
• Keep fences in good condition and prevent stray cattle from joining the herd

Trichomoniasis is a venereal disease of cattle that can cause a lot of headaches and economic loss. From early embryonic death and abortions to extended calving seasons and decreased weaning weights, T. foetus can wreak havoc on a cattle ranch. The trick to dealing with Trich is repeated testing for its presence, taking preventative measures, and maintaining a clean herd. As prevalence of T. foetus increases, more states will develop regulation programs. Indiana does not have a regulatory plan in place currently. Bulls shipped to states with regulations will need to be tested prior to their shipment. The ADDL at Purdue will accept direct smears and InPouch™ TF samples for microscopic evaluation. At this time, PCR is not available at ADDL. Be aware of Trich, and don’t let it trick you.

- by Craig Bowen, Purdue DVM Class of 2011
- edited by Dr. Bill Wigle, ADDL Pathologist

Cobo EE (2007). Sensitivity and specificity of culture and PCR of smega samples of bulls experimentally infected with Tritrichomonas foetus. Theriogenology 68: 853-860.

Kimsey P (1986). Bovine trichomoniasis. In DA Morrow (ed), Current Therapy in Theriogenology, 2nd Ed. WB Saunders Co, Philadelphia PA. pp 275-279.

Parker SC (2003). Diagnosis of trichomoniasis in 'virgin' bulls by culture and polymerase chain reaction. Can Vet J. 44: 732-734.

Peter D (1997). Bovine Venereal Diseases. In RS Youngquist(ed), Current Therapy in Large Animal Theriogenolgoy. WB Saunders Co, Philadelphia PA. pp 355-363.

Rae DC (2006). Tritrichomonas foetus. In Vet Clin N Amer Food Anim Prac. 22:595-611.

Skirrow S. (1987). Indentification of trichomonad carrier cows. JAVMA 191: 553-554.