Submitted to: International Congress of Parasitologists
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2006
Publication Date: July 10, 2006
Citation: Zarlenga, D.S., Rosenthal, B.M., Rosa, G., Pozio, E., Hoberg, E.P. 2006. Extant trichinella; the evolution of an archaic genus in a post-miocene world. International Congress of Parasitologists.
Parasitic nematodes of the genus Trichinella cause significant food-borne illness, and unlike the model and free-living nematode Caenorhabditis elegans, occupy a unique evolutionary position at the base of the phylum Nematoda. The forthcoming genome sequence of Trichinella spiralis will therefore provide invaluable comparative information about nematode biology. Until now, a basic framework for understanding the history of the genus Trichinella has been lacking. We therefore developed the first robust and comprehensive analysis of the phylogeny and biogeographic history of Trichinella based on variation in three genes (nuclear SSU rDNA and ITS2; mitochondrial LSU rDNA and COX I DNA) from all eleven recognized taxa. We conclude that: 1) although Trichinellidae may have diverged from their closest extant relatives during the Paleozoic, all contemporary species of Trichinella diversified within the last 20 million years, in Eutherian hosts, through geographic colonization, pervasive host-switching, and a transition to increasingly carnivorous hosts; 2) mammalian carnivores disseminated encapsulated forms from Eurasia to Africa during the late Miocene and Pliocene, and to the Nearctic across the Bering Land Bridge during the Pliocene and Pleistocene, when crown species ultimately diversified; 3) the greatest risk to human health is posed by species retaining an ancestral capacity to parasitize a wide range of hosts; and 4) early hominids may first have acquired trichinellosis as their diet shifted from herbivory to facultative carnivory on the African Savannah several million years prior to swine domestication.