Tritrichomonas foetus in young cats

Large intestinal diarrhea is a common complaint in young cats presenting to primary care veterinary practices, and Tritrichomonas foetus is an important differential diagnosis for this condition, as Dan Thompson describes.

Introduction

Diarrhea is a common reason for young cats to be presented to their primary care veterinarian. Practitioners are generally acutely aware of intestinal parasitic disease as a differential diagnosis for diarrhea, and many such patients will be treated empirically with anti-parasitic medications without further investigation. In many cases this appears to be effective, with relatively rapid improvement and cessation of clinical signs. Whilst the likes of Giardia and various helminths are likely to respond completely to such medications, the less-often considered Tritrichomonas foetus, a protozoan similar in appearance to Giardiaspecies, cannot be cleared by such empirical treatments. This parasite can be a source of profound frustration for both cat owners and their veterinary surgeons, as clinical signs may initially appear to respond to therapy with standard anti-parasitic medications, but often return quickly after treatment is discontinued. Furthermore, the parasite can be challenging to diagnose unless sought specifically. It is therefore likely that increased awareness of this pathogen could lead to faster recognition and more effective treatment in young cats with apparently unresponsive or recurrent diarrhea.

Incidence, prevalence and predispositions

Tritrichomonas foetus (T. foetus) has a worldwide distribution, with an estimated prevalence of between 10-59% ( 1 ). Relatively limited data exists on specific geographic prevalences; however one study in a population of UK cats estimated that roughly 20% of healthy cats may be carriers of the protozoa, and a separate study looking at the prevalence of T. foetus in diarrheic fecal samples submitted to a UK lab identified the parasite in 14.4% of samples ( 2 ). In the USA, on the other hand, a population of show cats was found to have a higher prevalence of T. foetus, at 31% ( 3 ).

The highest prevalence of T. foetus appears to be in purebred cats and cats kept as part of colonies. It has been demonstrated that individuals housed with a smaller number of square feet of housing space per cat were also more likely to be carriers of the disease, suggesting that population density plays a significant part in infection risk. Similarly, an increased risk of infection has been associated with the use of shared litter trays and with social grooming ( 2 ) ( 3 ).

Diarrhea caused by T. foetus is most commonly a disease of young cats, with a mean age of 8 months, and with greater than 75% of affected individuals being less than one year of age. However, cats of any age have the potential to carry the disease, and a proportion of these may develop clinical signs ( 1 ) ( 4 ). [...]