High prevalence of Trichomonas gallinae in wild columbids across western and southern Europe

Avian trichomonosis is known as a widespread disease in columbids and passerines, and recent findings have highlighted the pathogenic character of some lineages found in wild birds. Trichomonosis can affect wild bird populations including endangered species, as has been shown for Mauritian pink pigeons Nesoenas mayeri in Mauritius and suggested for European turtle doves Streptopelia turtur in the UK. However, the disease trichomonosis is caused only by pathogenic lineages of the parasite Trichomonas gallinae. Therefore, understanding the prevalence and distribution of both potentially pathogenic and non-pathogenic T. gallinae lineages in turtle doves and other columbids across Europe is relevant to estimate the potential impact of the disease on a continental scale.

Generally, turtle doves showed high prevalence of Trichomonas infection. Furthermore, the potentially pathogenic lineage A/B (or genotype B according to previous literature) was found in a recovering stock dove population. Both findings are worrying for these columbid species due to the occasional epidemic character of trichomonosis, which can have severe negative effects on populations.

We examined 281 samples from four wild columbid species for Trichomonas infection and determined the genetic lineages. The overall prevalence was 74%. There were significant differences between the species (P = 0.007). The highest prevalence was found in stock doves Columba oenas (86%, n = 79) followed by wood pigeons Columba palumbus (70%, n = 61) and turtle doves (67%, n = 65), while three of five collared doves Streptopelia decaocto (60%) were infected. We found seven different lineages, including four lineages present in columbids in the UK, one lineage already described from Spain and three new lineages, one of those found in a single turtle dove migrating through Italy and another one found in a breeding stock dove. Stock doves from Germany and collared doves from Malta were infected with a potentially pathogenic lineage (lineage A/B), which is known to cause lesions and mortality in columbids, raptors and finches. Conclusions: Generally, turtle doves showed high prevalence of Trichomonas infection. Furthermore, the potentially pathogenic lineage A/B (or genotype B according to previous literature) was found in a recovering stock dove population. Both findings are worrying for these columbid species due to the occasional epidemic character of trichomonosis, which can have severe negative effects on populations.