Tritrichomonas foetus and Mycoplasma felis coinfection in the upper respiratory tract of a cat with chronic purulent discharge

A 5-year-old indoor male neutered Siamese cat was presented with clinical signs of sneezing and chronic bilateral purulent nasal discharge. Multiple nasal cavity swabs were submitted for bacterial cultures, Mycoplasma felis-DNA qPCR, and cytology. M felis qPCR was positive and cytomorphologic diagnosis was severe, acute, purulent, rhinitis with intralesional protozoal microorganisms consistent with a Trichomonas spp. Nested PCR (nPCR) confirmed the diagnosis of Tritrichomonas foetus. Systemic therapy with doxycycline for M felis and metronidazole for T foetus was started with remission of clinical signs within 2 weeks; however, symptoms relapsed shortly after therapy was discontinued. This study represents the first documented case of T foetus associated with chronic nasal discharge in a cat, which supports the hypothesis that T foetus can live in the nasal cavity. It is also the first reported case of M felis and T foetus coinfection, which indicates that with mycoplasmal feline upper respiratory tract infections, T foetus should be considered as a coinfecting agent.