Novel avian oropharyngeal trichomonads isolated from European turtle doves (Streptopelia turtur) and racing pigeons (Columba livia) : genetic and morphometric characterisation of clonal cultures

Abstract

Extensive diversity and even new species have been described within the avian oropharyngeal trichomonad complex in recent years. In this study we developed clonal cultures from four isolates selected by their different ITS1/5.8S/ITS2 (ITS) genotype and their association with gross lesions of avian trichomonosis. Isolates were obtained from an adult racing pigeon (Columba livia) with clinical signs of avian trichomonosis, a juvenile wood pigeon (Columba palumbus) and an European turtle dove (Streptopelia turtur) without clinical signs, and a nestling of Eurasian eagle owl (Bubo bubo) with gross lesions. Multi-locus sequence typing analysis of the ITS, small subunit of ribosomal rRNA (SSUrRNA) and Fe-hydrogenase (Fe-hyd) genes together with a morphological study by optical and scanning electron microscopy was performed. No differences in the structures were observed with scanning electron microscopy. However, the genetic characterisation revealed three novel sequence types: one for the SSUrRNA region and two for the Fe-hyd gene. Clones from the Eurasian eagle owl and the wood pigeon were identified as Trichomonas gallinae analysing each locus, with an ITS genotype of T. gallinae-1 and T. gallinae-2 groups, respectively, which are commonly reported in wild birds from Europe and America. Clones of trichomonads from the racing pigeon and European turtle dove showed higher similarity with Trichomonas tenax and Tetratrichomonas canistomae than with T. gallinae strains at their ITS region, respectively. SSUrRNA sequences grouped clones in a T. gallinae, T. tenax and T. canistomae clade. Further diversity of T. gallinae was detected within the Fe-hyd locus. Morphometric comparison by optical microscopy with clonal cultures of T. gallinae (T. gallinae-1 and T. gallinae-2 ITS genotypes), revealed significant statistical differences on axostyle projection in the clone from European turtle dove, which was 1.6 μm longer (mean 8.2 μm) than the mean values reported for T. gallinae (6.4 μm). Possible new species within the Trichomonas genus were detected in isolates obtained from the racing pigeon and the European turtle dove, but further reports will be needed to confirm their host distribution.