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Tritrichomonas foetus


Synonym(s): T. foetus, T. fetus, Protozoa




  • Phylum: parabasalia.
  • Class: trichomonadea.
  • Family: trichomonadidae.
  • Feline parasite may be genetically distinct and may be referred to as Tritrichomonas blagburni.


  • The generic name is derived from the family Trichomonadidae, which are flagellate protozoa. The prefix (Tri) indicates the number of anterior flagella (3).

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Clinical Effects



  • There are no free-living stages.


  • The life cycle is simple with the trichomonads dividing longitudinally by binary fission.


  • Cats: feco-oral transmission. Occurs particularly from mother to kittens and in group housed cats with shared litter trays.
  • Cattle: bull to cow during mating.

Pathological effects

  • In cats, T foetus can infect and colonize the small and large intestines, but it is the colon where it can cause lymphocytic-plasmocytic (and also neutrophilic) inflammation; resulting in increased frequency of defecation, and the production of semi-formed to liquid feces, sometimes with fresh blood or mucus.
  • T. foetus infection mainly causes colitis Colitis (large bowel diarrhea). With severe diarrhea the anus may become inflamed and painful, and in some cases the cats may develop fecal incontinence.
  • Colonoscopy Colonoscopy may reveal inflamed thickened friable mucosa, plus or minus mucus and blood. Biopsies show inflammation but the parasites are infrequently seen.
  • Although the diarrhea Diarrhea: parasites may be persistent and severe, most affected cats are otherwise well, and do not show significant weight loss. However, occasional deaths have occurred in young kittens, probably resulting from secondary bacterial sepsis, and in very heavy burdens, the parasite may colonise the ileum, leading to some small bowel signs including weight loss.

Other Host Effects

  • Asymptomatic carriage of T. foetus is possible, and probably not uncommon. Usually only low numbers of the organism will be involved, but this situation can still have important implications in transmission and infection control.
  • Once clinical signs occur they can be waxing and waning, spontaneously resolve or, occasionally, result in intractable diarrhea that can last for up to 2 years.


Natural time course

  • As the immune system matures, many cats will eradicate the infection, or, control numbers of organisms such that clinical signs resolve.
  • Feeding either a simple highly digestible diet or a high fiber diet may result in improved fecal consistency, and this alone may aid control of clinical signs. Good attention to hygiene, reduction of overcrowding and stress reduction is also helpful.

Control via chemotherapies

  • There is no licensed treatment.
  • Ronidazole, a drug related to metronidazole Metronidazole, has proved safe and effective in many cats. However some patients have developed neurological signs, eg twitching and seizures, which have resolved on stopping the drug.
  • A dose of 30-50 mg/kg once to twice daily for two weeks is capable of both resolving clinical signs and potentially eradicating the T. foetus but can be associated with neurological side effects. Therefore, 20-30 mg/kg once daily is now recommended, and the dose should be further reduced for young kittens, or cats with hepatopathy; (10 mg/kg once daily for two weeks).
  • Ronidazole must be prepared into suitable sized capsules by a recompounding pharmacy Drug compounding (UK) Drug compounding (US).
  • Probiotics Probiotics and intestinal health may increase the chance of ronidazole treatment being effective.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Yao C, Köster L S (2015) Tritrichomonas foetus infection, a cause of chronic diarrhea in the domestic cat. Vet Res 46, 35 PubMed
  • Xenoulis P G, Lopinski D J, Read S A et al (2013) Intestinal Tritrichomonas foetus infection in cats: a retrospective study of 104 cases. J Feline Med Surg 15 (12), 1098-1103 PubMed
  • Gookin J L, Copple C N, Papich M G et al (2006) Efficacy of ronidazole for treatment of feline Tritrichomonas foetus infection. JVIM 20 (3), 536-543 PubMed.
  • Gookin J L, Stebbins M E, Hunt E et al (2004) Prevalence and risk factors for feline Tritrichomonas foetus and giardia infection. J Clin Microbiol 42 (6), 2707-2710 PubMed
  • Gookin J L, Birkenheuer A J, Breitschwerdt E B et al (2002) Single-tube nested PCR for detection of Tritrichomonas foetus in feline feces. J Clin Microbiol 40 (11), 4126-4130 PubMed.

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