The conundrum of feline trichomonosis: the more we learn the ‘trickier’ it gets

Abstract

Practical relevance: Trichomonosis of the large intestine of the cat was described as a cause of chronic diarrhea over 20 years ago. The trichomonad was identified as Tritrichomonas foetus, with a genotype that is distinct from venereal T foetus of cattle. Clinical challenges: Despite multiple means for diagnosis of the infection, including light microscopy, protozoal culture and PCR amplification using species-specific primers, tests with even greater sensitivity are needed. Feline trichomonosis is resistant to all commonly used antiprotozoal drugs. Ronidazole is currently the only drug demonstrated to be effective in eliminating the infection from cats; however, this drug has a narrow safety margin and clinical resistance is increasingly recognized. The more we learn about trichomonosis in cats, the more complicated and controversial the infection has become, ranging from what we should call the organism to whether we should even bother trying to treat it. Global importance: Feline trichomonosis is recognized to occur worldwide and is regarded as one of the most common infectious causes of colitis in the domestic cat. The infection is widespread in catteries and shelters; and, while remission of diarrhea may occur over time, persistence of the infection is common. The culprit of infectionTrichomonads are members of the class Parabasalia, order Trichomonadida. These protozoa reside as parasites or commensals of animals, where they live in mucous membrane-lined, anaerobic-tomicroaerophilic, non-sterile organ cavities such as the gastrointestinal and reproductive tracts. As is the case for most anaerobic protozoa, trichomonads lack many of their own biosynthetic pathways and rely on the salvage of nutrients from their host for survival. They are spindle to tear-drop shaped, highly motile flagellates, similar in size to Giardia species. only trophozoites are present in the life cycle (no true cyst stage), division is by binary fission, and transmission occurs directly between hosts via ingestion of trophozoites. Trophozoites bear characteristic numbers of anteriorly directed flagella. in addition there is a single, posteriorly directed flagellum that arises at the anterior end and courses along the body creating an undulating membrane, which is a characteristic feature. A rigid, rod-shaped organelle, the axostyle, runs through the trophozoite and protrudes from the posterior end (Figure 1

Fulminant Tritrichomonas foetus ‘feline genotype’ infection in a 3-month old kitten associated with viral co-infection

“…It is thought trichomoniasis resolves within 2 years in healthy cats, but in cats compromised with concurrent viral infection e.g. FPV, the time period until resolution is unknown (Gookin et al, 2017). Co-infection with other diarrheic agents such as FPV in this case may serve to increase the trichomonad disease burden.…”

“…Bovine T. foetus infections elicit a parasite-specific antibody response to adhesin and contact-dependent cytotoxicity, and these mechanisms may be hindered in immunosuppressed animals (Tolbert and Gookin, 2016;Voyich et al, 2001). Fluctuations in intestinal microbiota in the weaned kitten, influenced by co-infection of enteric pathogens, may have contributed to the trichomonad disease burden (Gookin et al, 2017;Šlapeta et al, 2015).…”

“…Co-infections with FPV or FCoV may influence prognosis of trichomoniasis in cats. Many cats infected with T. foetus undergo spontaneous resolution of their diarrhoea and become 'asymptomatic carriers', shedding low levels of the organism without clinically apparent diarrhoea (Gookin et al, 2017). It is thought trichomoniasis resolves within 2 years in healthy cats, but in cats compromised with concurrent viral infection e.g.…”

“…Tritrichomonas foetus 'feline genotype' causes waxing and waning large bowel diarrhoea, predominantly in multi-cat households (Gookin et al, 2017;Yao and Koster, 2015). Several studies have described coinfection with T. foetus and various pathogens, including Giardia, Toxocara, Eucoleus, Cryptosporidium, Cystoisospora, feline enteric coronavirus (FCoV) and Clostridium perfringens (Bell et al, 2010;Gookin et al, 2001Gookin et al, , 2004Kuehner et al, 2011;Paris et al, 2014;Profizi et al, 2013).…”

Comparison of multiplexed-tandem real-time PCR panel with reference real-time PCR molecular diagnostic assays for detection of Giardia intestinalis and Tritrichomonas foetus in cats

“…Giardia intestinalis and Tritrichomonas foetus are frequent and ubiquitous enteric protozoans affecting domestic cats (Gookin et al, 2017;Gruffydd-Jones et al, 2013;Šlapeta et al, 2015). Both parasites have a world-wide distribution in owned cats (Feng and Xiao, 2011;Yao and Koster, 2015).…”