Tritrichomonas foetus is a protozoan organism that causes venereal disease (trichomoniasis) in cattle. It is transmitted from infected bulls to cows during coitus and causes both infertility and abortion. This organism is also part of the normal GI flora of cats, but proliferates in the presence of diarrhea. In 1996, T. foetus was reported as a primary feline pathogen, transmitted by direct fecal-oral contact.

Thirty-six of 117 (31%) of presumably healthy cats being exhibited at a cat show were positive for T. foetus, their feces ranged from normal to diarrheic.

Trichomoniasis is an uncommon cause of chronic, large bowel diarrhea in cats. Affected cats typically live in multiple cat environments, and are generally healthy. The stool is cow-pie to semi-formed, has a foul odor, frequency is only slightly increased, and fresh blood or mucous are often present. Infected cats may have an inflamed anus, fecal incontinence, or rectal prolapse. The organism does not cause small intestinal disease, and infected cats are usually FeLV and FIV negative. There is no known age predilection.

Direct Fecal Smear. Use a warm saline mount and 400 x objective. A small amount of fresh feces from the cat's colon is sufficient, but organisms are likely to be found only in diarrheic stool, and the test is insensitive. Organisms have a characteristic pear-shaped appearance with anterior flagellae, and vigorous motility. They are much harder to find if cat has been on antibiotics, and are often misidentified as Giardia spp.

Inpouch® TF Culture System. About half of cases are positive with this method, which can be performed in-house.

PCR. More than 90% of infected cats are positive with the PCR method, but the drawback is cost. Samples need to be stored and transported at room temperature, as desiccation and refrigeration kills the organisms.

There is no known effective treatment, but the diarrhea is usually self-limiting within about 9 months. Metronidazole may be beneficial to reduce any concomitant bacterial infections. While diarrhea tends to recur, episodes tended to be mild, transient, and associated with stress; more than half of these cats remain T. foetus PCR positive. Management approaches in multi-cat environments include good hygiene, and keeping the environment clean and dry, to reduce spread of infection.

T. foetus has occasionally been diagnosed in dogs.

Reference: Gookin et al, ACVIM Proc. 2002