Trichobilharzia in the New World: Argentinian species offer a first glimpse of species diversity across hosts and the American continents.

BRANT S. V.; EBBS E; LOKER E. S.; VIOZZI G.P.; FLORES V.

Omaha Nebraska

Congreso; 90th Annual Meeting, American Society of Parasitologists.; 2015

American Society of Parsitology

The genus Trichobilharzia, commonly responsible for cercarial dermatitis, is globally distributed. But until recently, little was known about their species diversity in South America. This poses an interesting question, since some species of North American ducks are known to migrate to South America (and vice versa), and it is not known if South America duck species host distinct species of Trichobilharzia, or if they harbor the same species as found in North America, or both. Eleven species of indigenous South American ducks from northern Argentina were examined for schistosomes over the last two years. Two lineages of Trichobilharzia were found, one from one species of diving ducks and the other from three species of dabbling ducks, both endemic to South America. The species from diving ducks is distinct from dabbling ducks, but similar to the physid-transmitted North American species T. physellae, also from diving ducks. Similarly, the schistosome from South American dabbling ducks is distinct from, yet most similar to, the physid-transmitted species T. querquedulae from North American dabblers. This pattern reinforces the finding that at least within Clade Q of Trichobilharzia, one species group appears to prefer diving ducks (Netta, Aythya, Bucephala) and another prefers dabbling ducks (Anas), a trend also seen in flyways along the Eastern Hemisphere. This suggests that Clade Q has diversified into two host groups that are separated both by their descent and by their habitat use preferences. The global distribution of both groups of schistosomes has been favored by their use of now widely distributed snail host families, Lymnaeidae (Radix, Stagnicola) and in Physidae (Physa). Diving duck- or dabbler-specific schistosomes have been spread across two continents by virtue of their use of definitive hosts that are inherently migratory, and because their required snail host species are also widely distributed, yet we find that these lineages have undergone diversification between the two continents. This is explained in part by the particular host ecologies (and distributions) most frequently encountered by the schistosome, as well as the fact that the duck host that travels the farthest may mix with more local populations infrequently.