Tritrichomonas foetus, also know as “tritrich” or T. foetus, is a relatively new parasite of cats which is gaining recognition in the shelter community. T. foetus is a flagellated protozoa, which is similar to Giardia spp. in many ways. T. foetus is most common in catteries and sanctuaries, but can also be found in shelters or privately owned animals.
Like many gastrointestinal parasites, T. foetus is spread by fecal contamination (shared litter boxes, grooming after stepping in feces, etc.). Infected cats can have gassy, malodorous diarrhea, or no clinical signs at all. In private practice many owners may be reluctant to treat, as signs can be mild to non-existent. However, this parasite can be devastating in a shelter situation due to the chronic nature of infection. Cats which are untreated can take up to two years to clear the infection, and some remain infected for life.
T. foetus can be challenging to diagnose, for a number of reasons. Unlike most parasites, which can be found on fecal flotation, T. foetus requires specialized testing. The parasites are rare, so finding them can be difficult. Additionally, antibiotics, contamination, and poor sample handling can cause false negative results. T. foetus can be diagnosed by either fecal smear, fecal culture, or DNA testing (PCR). DNA testing is the best, but the most expensive and often requires the use of a referral laboratory. Fecal culture and smears are less likely to find the infection, and require some skill on the person doing the test. Watch the following video to see why T. foetus can sometimes be mistaken for Giardia spp. under the microscope.
While diagnosis can be hard, treatment can be even harder. The most commonly used drug is ronidazole, which is in the same drug family as metronidazole. Ronidazole is most commonly used as an anti-protozoal and anti-bacterial agent in turkeys, pigeons and pigs. Ronidazole is not FDA approved for use in cats and poses human-health risks. While initial studies have shown that ronidazole is a promising treatment option in cats with T. foetus, some cats experience severe side effects. Signs of toxicity include lethargy, anorexia, stumbling gait, seizures, and even death. Treatment failure is common, leaving shelters with cats that have chronic, infectious diarrhea, which will be challenging to manage and to adopt out.
T. foetus is easily killed in the environment; thus the best way to control spread of infection is through sanitation and disinfection. Infected or suspect cases should be isolated from healthy cats, especially those who are sick or immuno-compromised. If you think your shelter cats may have T. foetus , then please contact your local shelter veterinarian, or the Cornell University Shelter Medicine Program for assistance with diagnostics and treatment.
For more information about Tritrichomonas foetus, please visit Dr. Jody Gookin’s website: http://www.JodyGookin.com
Is there any information about what to do if the cat has been treated 3 times with Ronidazole and is still testing positive?
Hi Ellen — One of the struggles with T. Foetus is that in spite of improvement and even apparent cure, many cats will break with infection again. I am afraid I do not have any additional suggestions around this if you have already done the recommended treatment duration and dose, and you have worked to prevent recontamination through litterbox management and cleaning and prevention of exposure to other infected cats. Most cats will clear within two years, but often treatment is unsuccessful even when you do everything right.