Tritrichomonas foetus in Cats

PetMD Editorial
By PetMD Editorial on Mar. 19, 2010
Tritrichomonas foetus in Cats

Feline Tritrichomonas foetus Parasitic Infection


Cats and kittens from shelters and catteries are at higher risk of contracting an intestinal parasite that causes a long-term, foul-smelling diarrhea. The parasite, Tritrichomonas foetus (T. foetus) is a single-celled protozoan that lives in the colon of cats and is shed in the feces.


Symptoms and Types


Younger animals are most likely to have diarrhea as the result of infection. Adult cats may or may not show signs, but can still be carriers of the parasite, passing it into the environment through their feces, and putting uninfected cats at risk of acquiring it. Symptoms may not appear in an infected animal for years after being exposed.


The main symptom is a longstanding bout of loose smelly stools, sometimes mixed with blood or mucus. Cats may have difficulty passing the loose stools and strain to empty the bowels. Stool may leak out of the anus and cause redness and pain around the area.




Cats that share a litter box can pick up the organism by stepping in the litter box and then later licking its feet or fur. The organism is then carried to the colon, where it thrives. This is why animals that live in close proximity are all likely to be carrying the parasite. Cats can have symptoms that last for years and can possibly remain infected for life without ever being diagnosed.




Samples of fresh fecal matter can be examined in several ways to see if the parasite is present. Typically, the veterinarian will prefer to collect a sample during an examination, as the feces must not be mixed with cat litter or dried out.


An easy test that can be run by your veterinarian includes examination of a fecal smear under a microscope. Other test methods include culturing fecal matter; a DNA test for presence of the organism; and a tissue sample (biopsy) of the colon.




Currently, the most effective known therapy for cats diagnosed with T. foetus is a drug called ronidazole. This antiprotozoal drug is not currently approved for use in cats in the United States, but your veterinarian may choose to prescribe it. You or your veterinarian will need to get this drug from a special compounding pharmacy that custom blends the medication. The affected cat should be isolated from other cats in the household until the end of treatment to prevent them from becoming infected as well.


Ronidazole is given orally once a day for two weeks. During treatment, cats should be watched closely for any adverse reactions to the drug. Potential side effects of ronidazole are neurological and include difficulty walking, loss of appetite (anorexia), and possible seizures. If your cat shows any signs of toxicity, treatment must be discontinued and your veterinarian must be consulted.


Living and Management

During and following treatment, cats should be given a very digestible diet to help regulate their bowel movements. The litter box environment should be keep well disinfected, dry, and changed regularly during treatment to prevent re-infection with T. foetus.



There is no vaccine or preventive medication that can be given for this organism. Cats from breeders and shelters should be monitored closely for signs of potential infection. In addition, new cats should not be introduced to the other cats in a household until they have been examined by a veterinarian and cleared.

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