Novel trichomonads in cloacal samples of shorebirds: Charadriimonas elzamajori gen. nov., sp. nov. from the Ruff

Trichomonads (Metamonada: Parabasalia: Trichomonadea) are flagellated protozoan parasites associated with mucosal surfaces of vertebrates. While their diversity in domestic poultry is well-studied, corresponding data are lacking from several categories of wild-living avian hosts, including shorebirds. During the spring and autumn of 2025 cloacal swabs from 36 Ruffs ( Calidris pugnax ) and 56 individuals of five additional shorebird species were analyzed for trichomonads using morphological assessment, 18S rRNA and alpha-tubulin gene, as well as ITS region PCRs followed by sequencing and phylogenetic analyses. Trichomonad DNA was detected in 73.7% of Ruffs during spring, while prevalence dropped to 5.88% in the autumn. Morphological examination revealed trophozoites with five anterior flagella, but short axostyle. Phylogenetically, sequences from Ruffs formed a distinct clade. Closely related 18S rRNA genotypes were also detected in Common Snipe ( Gallinago gallinago ) and Little Ringed Plover ( Thinornis dubius ). Based on combined morphological and phylogenetic evidence obtained from Ruffs, a novel genus and species, Charadriimonas elzamajori gen. nov., sp. nov. is described. Seasonal and age-related differences in infection prevalence and lower or higher genetic diversity imply the impact of mating strategies on the epidemiology and raise the possibility of venereal transmission. The findings highlight shorebirds as previously underestimated hosts of trichomonads which should be evaluated further in this context, particularly in habitats shared with grazing livestock.