Tritrichomonas foetus
Dr Emi Barker examines the clinical signs, diagnosis, treatment and prevention of a single-celled protozoan parasite that lives within mucus covering the mucosa surface of the distal ileum, caecum and colon of cats.
Infection causes inflammation of the mucosa resulting in predominantly large intestinal diarrhoea. Risk factors include young age and coming from a multi-cat or breeding household. Transmission is via the faeco-oral route, with organisms remaining viable in moist faeces for a small number of days.
Different strains of Tritrichomonas foetus (T. foetus) infect the reproductive tract of cattle and colonise the nasal mucosa and gastrointestinal tract of pigs. This agent is rarely zoonotic, but good hygiene practice should be applied when handling infected cats or their waste products particularly by immunosuppressed individuals.
Clinical signs
Although cats of any age can be affected, younger cats are over represented. Most infected cats present with a chronic history of waxing and waning, malodourous, large intestinal diarrhoea with variably increased frequency, increased mucus, haematochezia, tenesmus, and flatulence. In some cats this can progress into faecal incontinence, perianal swelling and dermatitis. Cats are often otherwise well in themselves.
Diagnosis
Diagnosis is based on direct microscopic visualisation of organisms, culture (using the "InPouch" system) or detection of organism deoxyribonucleic acid (DNA) by polymerase chain reaction (PCR) in faeces, faecal mucus or colonic wash. Microscopically, Trichomonas organisms have a similar size and shape to Giardia species, but with a different movement pattern (T. foetus is rapid and jerking; Giardia species are slow, with a falling-leaf movement). False negative results can occur with all methodologies, therefore, as the colonic mucus is the site of infection, PCR of colonic wash fluid increases the sensitivity of detection in infected cats Gookin and others, 2017).
Treatment and prevention
Although clinical signs may improve on antibiotics, diarrhoea typically recurs when these are stopped. Feeding of bland or high-fibre diets have also been suggested to be beneficial. Clinical signs can resolve without treatment but affected cats likely remain a reservoir of infection.
The only agent with proven efficacy against T. foetus is ronidazole, which is effective in around two thirds of cases (Xenoulis and others, 2013). Current recommended doses are 20-30mg/kg orally, once daily for 14 days, and should be based on accurate weight measurement (Gruffydd-Jones and others, 2013). In young kittens below 12 weeks of age, or cats with hepatic dysfunction, doses should be reduced to 10mg/kg to minimise risk of adverse effects. Administration of a probiotic (for example, Pro-Kolin Enterogenic, Protexin) for four weeks is also recommended (Lalor & Gunn-Moore, 2012).
Adverse effects of ronidazole are primarily related to neurotoxicity (lethargy, inappetence, ataxia, tremors, and seizures) with vomiting less frequent. If adverse effects manifest, the ronidazole should be immediately discontinued. Metronidazole increases the risk of toxicity, so should not be given concurrently. As it is teratogenic, ronidazole should not be administered to pregnant or nursing queens. Obtaining informed, written owner consent prior to treatment is strongly recommended. Owners should wear gloves when administering.
At the time of writing, ronidazole is not available as a licensed product for use in cats. Only two UK compounding pharmacies supply reformulated capsules or liquid direct to veterinary practices – Nova Laboratories and Summit Veterinary Pharmaceuticals.
To reduce the risk of re-infection and transmission, good hygiene practice (for example, frequent litter tray emptying and cleaning) should be employed and, ideally, infected cats isolated. The risks and benefits of treating all cats within a household in should be considered carefully.
References
- Gookin, J. L., Hanrahan, K. & Levy, M. G. (2017) The conundrum of feline Trichomonosis. Journal of Feline Medicine and Surgery 19, 261-274
- Gruffydd-Jones, T., Addie, D., Belak, S., Boucraut-Baralon, C., Egberink, H., Frymus, T., Hartmann, K., Hosie, M. J., Lloret, A., Lutz, H., Marsilio, F., Mostl, K., Pennisi, M. G., Radford, A. D., Thiry, E., Truyen, U. & Horzinek, M. C. (2013) Tritrichomoniasis in cats: European Advisory Board on Cat Diseases (ABCD) guidelines on prevention and management. Journal of Feline Medicine and Surgery 15, 647-649
- Gunn-Moore, D. A., McCann, T. M., Reed, N., Simpson, K. E. & Tennant, B. (2007) Prevalence of Tritrichomonas foetus infection in cats with diarrhoea in the UK. Journal of Feline Medicine and Surgery 9, 214-218
- Lalor, S., Gunn-Moore, D (2012): Effects of concurrent ronidazole and probiotic therapy in cats with Tritrichomonas foetus-associated diarrhoea. (Abstract). Journal of Feline Medicine and Surgery 14, 651
- Payne, P. A. & Artzer, M. (2009) The biology and control of Giardia spp and Tritrichomonas foetus. Veterinary Clinics: Small Animal Practice 39, 993-1007
- Xenoulis, P. G., Lopinski, D. J., Read, S. A., Suchodolski, J. S. & Steiner, J. M. (2013) Intestinal Tritrichomonas foetus infection in cats: a retrospective study of 104 cases. Journal of Feline Medicine and Surgery 15, 1098-1103.