Abstract
Avian trichomonosis is a widespread disease in columbids and other birds, caused by ingestion of the unicellular flagellate Trichomonas gallinae which proliferate primarily in the upper respiratory tracts. Studies using genetic analyses have determined some highly pathogenic lineages in birds, but the prevalence and distribution of potentially pathogenic and non-pathogenic T. gallinae lineages in wild birds is still not well known. We examined 440 oral swab samples of 35 bird species collected between 2015 and 2017 in Hesse, central Germany, for Trichomonas spp. infection and for determining the genetic lineages. Of these birds, 152 individuals were caught in the wild and 288 individuals were admitted from the wild to a veterinary clinic. The overall Trichomonas spp. prevalence was 35.6%. We observed significant differences between bird orders, with the highest prevalence in owls (58%) and columbids (50%), while other orders had slightly lower prevalences, with 36% in Accipitriformes, 28% in Falconiformes and 28% in Passeriformes. Among 71 successfully sequenced samples, we found 13 different haplotypes, including two previously described common lineages A/B (20 samples) and C/V/N (36 samples). The lineage A/B has been described as pathogenic, causing lesions and mortality in columbids, raptors and finches. This lineage was found in 11 of the 35 species, including columbids (feral pigeon, woodpigeon, stock dove), passerines (greenfinch, chaffinch, blackbird) and raptors (common kestrel, sparrowhawk, red kite, peregrine falcon and common buzzard). One new lineage (R) was found in a sample of a chaffinch. In conclusion, we found that the prevalence of Trichomonas spp. infection in wild birds was high overall, and the potentially pathogenic lineage A/B was widespread. Our findings are worrying, as epidemic outbreaks of trichomonosis have already been observed in Germany in several years and can have severe negative effects on bird populations. This disease may add to the multiple pressures that birds face in areas under high land-use intensity.
Highlights
Trichomonosis is regarded as an emerging infectious disease in wild birds in Europe [12], and in the present study, we confirmed the widespread prevalence of this pathogen in several bird orders beyond Columbiformes in Germany, including the potentially pathogenic lineage A/B
We observed a high prevalence of Trichomonas spp. infections in wild birds in central Germany
Trichomonas spp. was widespread among other bird orders, with a prevalence of 28–36% observed in Passeriformes, Strigiformes and diurnal raptors (Accipitriformes/Falconiformes, Table 1)
Summary
The flagellate parasite Trichomonas gallinae (Rivolta 1878) infects captive and wild birds across the world and can lead to the avian disease called trichomonosis [1]. Trichomonas infections in wild birds in Germany include white to yellowish oral and pharyngeal lesions. As inflammation and ulceration progress, the lesions may extend to the esophagus, crop and proventriculus and may cause obstipation. Spreading of the pathogen is possible by penetrating the underlying tissues and inner organs such as the liver [2]. Because similar symptoms have been observed in fossils of dinosaurs, trichomonosis is believed to be an ancient pathogen [3]
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