Objective —To determine the long-term outcome of cats infected with Tritrichomonas foetus and identify treatment and management strategies influencing resolution of infection or associated diarrhea.

Design —Prospective study.

Sample Population —26 cats with T foetus -associated diarrhea at least 22 months prior to the study.

Procedure —A standardized survey regarding clinical course and management was administered to owners of cats with T foetus infection and associated diarrhea. Fecal samples were obtained from each cat; the presence of T foetus was assessed via microscopic examination of smears, culture in commercial media, and polymerase chain reaction amplification of T foetus rDNA involving species-specific primers.

Results —Survey responses were obtained from owners of all 26 cats. Twenty-three cats had complete resolution of diarrhea a median of 9 months after onset. Analysis of fecal samples obtained from 22 cats revealed persistent T foetus infection in 12, with a median of 39 months after resolution of diarrhea. History of implementation of a dietary change, treatment with paromomycin, or higher numbers of cats in the household was associated with significantly longer duration of time to resolution of diarrhea.

Conclusions and Clinical Relevance —Results suggested chronic T foetus -associated diarrhea in most cats is likely to resolve spontaneously within 2 years of onset. Chronic infection with T foetus (without clinical signs) after resolution of diarrhea appears to be common. Although often temporarily effective in decreasing severity of diarrhea, attempts to treat cats with T foetus infection may result in prolongation of time to resolution of diarrhea. ( J Am Vet Med Assoc 2004;225:888–892)