Oral Presentation 64th International Conference of the Wildlife Disease Association 2015

The evolution of Trichomonas and the pigeons and doves: a unique story in Australasia  (#61)

Andrew Peters 1 , Shane Raidal 1
  1. Charles Sturt University, NSW, Australia

Trichomonosis is amongst the earliest recorded diseases of birds, and Trichomonas gallinae is regarded as a significant pathogen in birds of prey and columbids. In recent years the protist has expanded its host range and caused population declines of passerines in Europe and North America.

Australasia is home to more than 40% (134 species) of the world’s pigeons and doves (family Columbidae). These have a deep evolutionary history in the region, having evolved in Gondwana more than 65 Mya, and exhibit marked phenotypic and ecological diversity. Of particular ecological significance are thefruit-doves, which are the most effective seed-dispersers in the region’s rainforests. In order to examine the potential impact of T. gallinae on Australia’s columbid fauna, we sampled more than 500 individuals of 25 species of pigeons and doves for Trichomonas in Australia and Papua New Guinea.

We found T. gallinae in healthy individuals of two introduced species of pigeons, as well as in four wild birds of prey with trichomonosis. By contrast, almost all wild columbid species were infected with novel lineages of Trichomonas and were asymptomatic. We discovered six new lineages of Trichomonas, more than doubling its previously described genetic diversity. Our findings suggest that Trichomonas is deeply co-evolved with columbids in Australasia, but that this organism is adept at host-switching. This may be a salient feature in the recent emergence of trichomonosis in other birds and in a likely spillover from columbids to humans giving rise to T. vaginalis (the most common sexually transmitted infection of people) at some point in the past, an event which is suggested by our data.

Potential evolutionary trade-offs for infection with Trichomonas in columbids will be discussed, as well as the risk to native columbids and birds of prey from the introduced pathogen T. gallinae.