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Fecal sample collection and treatment history of Tritrichomonas fetus

Hedgespeth, B. A., Stauffer, S. H., Robertson, J. B., & Gookin, J. L. (2020). Association of fecal sample collection technique and treatment history with Tritrichomonas foetus polymerase chain reaction test results in 1717 cats. J Vet Intern Med, 15727.

Trichomoniasis in cats in a colonic infection caused by the protozoan Tritrichomonas foetus.  Infection with his organism may be subclinical, or may be associated with chronic large bowel diarrhea. Infection is most common in young cats and may be associated with certain breeds. Testing for T. foetus is notoriously difficult, and many techniques have been described to improve the sensitivity. PCR is considered the most sensitive methodology, however different methods of stool collection have been described. Samples from deeper in to the colon are generally preferred, and so the use of a fecal loop (a plastic implement to “scrape” stool out of the colon) or a colonic flush (insertion and withdrawal of a deep saline enema) have been proposed as more sensitive than other methods. Treatment of trichomonas is equally challenging. While ronidazole is the only drug known to have reliable efficacy, other antimicrobials may partially suppress the organism.

The purpose of this study was to describe the effects of fecal loop vs colonic flush techniques on the sensitivity of PCR testing, and to determine if treatment history effects the results of PCR testing. The study was designed as a retrospective study evaluating samples submitted from a university teaching hospital over a 5 year period. Samples were submitted from veterinarians along with a submission form indicating signalment, method of collection, and prior treatments.

1808 samples from 1717 cats were submitted (repeat testing was performed on 87 cats). Samples were overwhelmingly from the USA, with small numbers from Canada, Mexico, England, and Taiwan. Median age was 1 year. 41 breeds were represented, with the most common being the domestic cat. The most common reason for submission was a history of diarrhea, followed by exposure to positive cats.

31% of cats had samples collected by voiding, 23% by a fecal loop, and 46% by colonic flush.

274 cats (16%) tested positive for Tritrichomonas on initial submission. Of the 19 cats who tested positive and were treated with ronidazole prior to repeat testing, 4 (21%) remained positive. All cats that remained positive were from multi cat households, suggesting possible re-infection.

There was no significant association between PCR positivity and number of cats in the household. No association was found between sex or life stage and positivity, though a weak but significant trend towards increased likelihood of a positive test with younger age was present. While several breeds were initially identified as higher risk, on multivariate regression analysis only Abyssinians had a significantly increased odds of infection.

Samples collected using a fecal loop technique were 2.04 times more likely to test positive than samples using a colonic flush. There was no significant difference between voided and flush samples. There was no association between previous treatment with previous antibiotics, antiparasitic, anticoccidials, or steroid and PCR positivity.

There were several limitations to this study. While large, the sample was also geographically diverse and data was not stratified by region. Further, once stratified into subgroups (such as cats testing positive and being treated with ronidazole), these subgroups were quite small.   The prevalence data is likely to be significantly biased, as only animals suspected of having trichomoniasis were enrolled. As such, members of breeds anecdotally reported to have a higher rate of trichomonas infection may have been selectively sampled. The large number of veterinarians collecting and submitting samples may also have induced variation into the data.

Overall, this study suggests that in cats suspected of having trichomoniasis, a fecal loop technique is the best collection method. Pre-treatment with medications does not seem to affect the sensitivity of PCR testing. Finally, ronidazole may have a 21% failure rate in treating trichomonas, reinforcing the need for more effective medications. (MRK)

See also:

Foster DM, Gookin JL, Poore MF, Stebbins ME, Levy MG. Outcome of cats with diarrhea and Tritrichomonas foetus infection. J Am Vet Med Assoc. 2004; 225: 888‐892.