Pentatrichomonas hominis infection in two domestic cats with chronic diarrhea

CASE SERIES SUMMARY: Chronic diarrhea is a common and recurring problem in feline medicine. Intestinal trichomonads have been reported as causative agents of diarrhea in cats. While Pentatrichomonas hominis is considered commensal, Tritrichomonas foetus has been found to cause feline large bowel diarrhea in cats. In our report, two young cats infected with the feline leukemia virus (FeLV) and presenting with chronic diarrhea were identified as having trichomonads in their feces, based on direct examination and fecal culture. Molecular assays (PCR and DNA sequencing) revealed that the parasite involved was P hominis, not T foetus, as was suspected. The animals had already been subjected to ineffective therapy with metronidazole, and after the use of ronidazole, their feces became dry and formed. RELEVANCE AND NOVEL INFORMATION: This case report describes P hominis infection as a possible cause of chronic diarrhea in two young cats also infected by FeLV. The parasite was probably resistant to metronidazole, the drug of choice in the literature, and sensitive to ronidazole. Although considered commensal, P hominis infection should be evaluated as a differential diagnosis in cats with chronic diarrhea, especially those that are immunocompromised. Moreover, a combination of techniques such as direct examination and/or fecal culture and PCR is essential for an accurate diagnosis of P hominis infection.