Feline Tritrichomonas Foetus Infection: A Review

Maigan Espinili Maruquin

Structure and Epidemiology

The protozoan parasite Tritrichomonas foetus has sudden emergence of its syndrome in the 1990s causing feline intestinal tritrichomoniasis and has then attracted feline medicine studies (Levy, Gookin et al. 2003, Bell, Gowan et al. 2010) (Levy, Gookin et al. 2001 ). At a range of 10- 31%, infected cats in UK and USA comes from young, pedigree cats in multi-cat environment (Gookin, Levy et al. 2001, Foster, Gookin et al. 2004, Gookin, Stebbins et al . 2004, Gunn-Moore, McCann et al. 2007, Frey, Schild et al. 2009, Stockdale, Givens et al. 2009)( Gunn-Moore D, Tennant B, 2007)(Bell, Gowan et al. 2010). An estimate 30% of purebred cats in USA are suggested infected by T. foetus (Gookin, Stebbins et al. 2004, Gookin, Stauffer et al. 2010).

The T. foetus , like other trichomonads, has only trophozoite stage, however, it has a pseudocyst stage (Lipman NS, et. al., 1999) (Pereira-Neves, Ribeiro et al. 2003, Benchimol 2004, Mariante, Lopes et al. 2004, Yao and Köster 2015). Therefore, cats are presumed to be infected via direct contact due to the absence of the cyst stage (Zajac AM, Conboy GA, 2006). The parasite is pear- or spindle-shaped, having three anterior flagella and one posterior flagellum. With its size of approximately 10-25 μm in length and 3-15 μm in width, the undulating membrane extends along the whole length of the body which emerges as the posterior flagellum. This trophozoite reproduces asexually by longitudinal binary fission (Yao and Köster 2015).


Fig. 01. Morphologic structure of the Tritrichomonas foetus 

Infected cats were reported to experience chronic large bowel diarrhea as the parasite was found in the feline intestine (Foster, Gookin et al. 2004, Payne and Artzer 2009). Reports also showed the presence of the organism in the feline uterus (Dahlgren, Gjerde et al. 2007). Further, the isolates of T. foetus from cattle are known to be infectious for the cats, while the isolates of the same species from cats are infectious to cattle (Stockdale, Dillon et al. 2008, Walden, Rodning et al. 2008, Payne and Artzer 2009).


Clinical Signs/ Pathogenesis

Despite suggestions of strong association of feline T. foetus and chronic diarrhea (Gookin, Stebbins et al. 2004, Mardell and Sparkes 2006, Gunn-Moore, McCann et al. 2007, Burgener, Frey et al. 2009, Holliday, Deni et al. 2009, Pham 2009, Stockdale, Givens et al. 2009, Kuehner, Marks et al. 2011), whether the parasite alone is sufficient to cause clinical signs or the foetus-associated diarrhea, being a primarily multifactorial disease involves concurrent infection with other enteropathogens, host and environmental factors (Gookin, JL, et. al., 1999) (Gookin, Levy et al. 2001, Bissett, Gowan et al. 2008, Stockdale, Givens et al. 2009, Kuehner, Marks et al. 2011).

It is possible that the trophozoites are transmitted by a fecal- oral route from an infected to uninfected cat (Yao and Köster 2015). Symptoms may appear early as 2 to 7 days after orogastric inoculation (Gookin, Levy et al. 2001, Yao and Köster 2015). Whereas, infected cats showed anorexia, depression, vomiting and weight loss while experimental infections also reported vomiting and fever (Mardell and Sparkes 2006, Xenoulis, Lopinski et al. 2013, Yao and Köster 2015)( Stockdale, H., et al., 2007). Chronic large bowel diarrhea, associated with blood, mucus, flatulence, tenesmus, and anal irritation were also reported (Foster, Gookin et al. 2004, Gookin, Stebbins et al. 2004, Payne and Artzer 2009, Stockdale, Givens et al. 2009). With the characteristic of the trichomonads as commensal organisms, some hosts show no clinical signs and are asymptomatic (Payne and Artzer 2009).

In some studies, the parasite, with its surface located antigen, was detected on epithelial surface and within the superficial detritus of the cecal and colonic mucosa (Gookin, Levy et al. 2001, Yao and Köster 2015), while naturally infected cats showed parasite in close proximity to the mucosal surface and less frequently in the lumen of colonic crypts (Yaeger and Gookin 2005, Yao and Köster 2015). Conclusively, T. foetus trophozoites can be detected in epithelial surface and crypts of cecum and colon (Yao and Köster 2015). Mechanisms were then described to include possibilities of alterations in the normal intestinal flora, adherence to the epithelium, and elaboration of cytokines and enzymes (Payne and Artzer 2009).


For cats <6months old with recent clinical signs of chronic large bowel diarrhea, infection with T. foetus infection is suspected (Yao and Köster 2015).

Diagnosis of the T. foetus infection may be conducted via direct observation of the flagellates in fresh or cultured feces (Payne and Artzer 2009) or on a saline diluted direct fecal smear (Yao and Köster 2015). The trophozoites of T. foetus are difficult to distinguish from Giardia spp and other nonpathogenic intestinal trichomonads. However, although the size of T. foetus and Giardia spp are almost the same, they move differently. The movement of Giardia spp. resembles the fall of a leaf while trichomonads move erratically (Yao and Köster 2015)( Gookin JL, Levy MG, 2008).

Feline feces can be cultivated and be tested in commercially available InPouch™ TF medium (Payne and Artzer 2009, Yao and Köster 2015) or DNA extraction and amplification of T. foetus rDNA by the use of PCR from feces samples can be conducted (Gookin, Stebbins et al. 2004, Manning 2010, Yao and Köster 2015). Moreover, other causes of diarrhea, like bacterial, viral, other parasites, and nutritional problems should be ruled out before a diagnosis of tritrichomoniasis can be made (Payne and Artzer 2009).

Treatment and Disease Managements

The T. foetus infection in cats has no approved treatment. While treating infected animals is difficult, success is also limited (Payne and Artzer 2009). Literatures have used therapeutics including paromomycin, fenbendazole, furazolidone, nitazoxanide, metronidazole, tinidazole and ronidazole (Gookin, Breitschwerdt et al. 1999, Gookin, Levy et al. 2001, Yao and Köster 2015).

The ronidazole is not registered for human or veterinary use (Yao and Köster 2015) however, it showed effectiveness in experimentally infected cats (Gookin, Copple et al. 2006) (Gookin JL, Dybas D, 2008). Due to possible neurologic side effects, caution is observed in using this drug. Moreover, relieving diarrheal symptoms such as dietary changes have also failed to help resolve symptoms (Payne and Artzer 2009).

Therefore, sanitation of the environment and the animals in a cattery is critical. This parasite do not survive outside the host for a long time, but cats are fastidious and will definitely re-ingest these parasites readily (Payne and Artzer 2009).



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