Zoonotic Trichomonas tenax and a new trichomonad species, Trichomonas brixi n. sp., from the oral cavities of dogs and cats.

Trichomonads are known to inhabit the oral cavities of various mammals, including dogs, cats and horses. However, little attention has been paid to species identification, prevalence and zoonotic potential of these parasites, although their hosts live in close proximity with humans. According to the original description, oral trichomonads in dogs and cats belong to the genus Tetratrichomonas. Interestingly, later investigations suggested that the oral cavities of dogs and cats could be infected with different species of the genus Trichomonas, including the human oral cavity parasite Trichomonas tenax. Thus, in this study we investigated the occurrence of oral trichomonads in 111 domestic dogs and 122 cats using cell cultivation methods, nested PCR analyses, and the sequencing of ITS1-5.8rRNA-ITS2 regions. We found that both dogs and cats harbour T. tenax, with prevalences of 8.1% and 4.1%, respectively. Considerably more dogs were infected with different species of the genus Trichomonas (30.6%), which we also identified in cats (6.6%). An analysis of the potential risk factors suggested that dogs of more than 3years old or with dental disease signs are more frequently infected with Trichomonas sp. than younger dogs or dogs without the disease signs, and that crossbreed dogs revealed increased rates of infection in comparison with purebred dogs. An analysis of the cat population suggested that Trichomonas sp. infection is lower in younger and crossbreed cats. Although the morphology of Trichomonas sp. is very similar to that of T. tenax, based on a phylogenetic analysis of ITS1-5.8rRNA-ITS2 regions and the ssrRNA genes, we consider Trichomonas sp. to represent a new trichomonad species, for which we propose the name Trichomonas brixi.