Submitted to: Infection, Genetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2009
Publication Date: 4/24/2009
Publication URL: http://doi:10.1016/j.meegid.2009.03.003
Citation: Pozio, E., Hoberg, E.P., Larosa, G., Zarlenga, D.S. 2009. Molecular Taxonomy, Phylogeny and Biogeography of nematodes belonging to the Trichinella genus. Infection, Genetics and Evolution. 9(4):606-616. Interpretive Summary: Recent history depicts the phylum Nematoda being separated into two classes, the Adenophorea and Secernentea. Classically, the genus Trichinella has been grouped with the Adenophorea; however, the latest molecular data has begun to question this entire classification scheme. Information has recently surfaced suggesting that Trichinellidae and Trichuridae diverged from a common ancestor greater than 300 million years ago (Ma) though, little is known of the biogeography and biohistory of host-parasite assemblages within the genus Trichinella. Nematode characteristics that are universally conserved across the phylum could have a great value for control strategies with broad application. Herein we evaluate and recapitulate all current data on this genus and present new phylogenetic supertrees incorporating the recently discovered South American isolate of Trichinella as well as the genetically distinct isolates of T. pseudospiralis. This information, and that yet to come in conjunction with the relatively recent genome sequence will advance research related to parasitic nematodes across the phylum, and will assist in developing conserved control strategies currently unattainable due to the dearth of genetic information relating these organisms.
Technical Abstract: Studying parasites of the genus Trichinella provides scientists of today many advantages. This is a group of zoonotic nematodes that circulate freely among wildlife hosts with one in particular, Trichinella spiralis that is particularly well adapted to domestic swine. Indeed, recent reports suggest that human infections from hunted stock are on the rise worldwide and numerous countries still experience problems with Trichinella spiralis in their domestic food supplies. Trichinella is an ancient genus, whose members are easy to propagate in a laboratory setting, have been used as models to investigate host-parasite relationships and parasitism among Clade I organisms, and represent a critical but poorly investigated link in the evolutionary timeline between the phylum Nematoda and other Metazoans. Its importance in better understanding the tree of life was so recognized that in 2004, the genome of T. spiralis was carefully selected as one of only nine key non-mammalian organisms to have its genome sequenced to completion in order to advance our awareness of essential structural and functional components of life. Since it was first discovered in 1835, our concept of this genus has expanded from being monospecific to being a nematode group of great complexity encompassing at least eight species and to date, four other genotypes of undetermined taxonomic rank. Inasmuch as discerning morphological data has been scant, our understanding of the genus has been relegated to compiling molecular, biochemical and biological data into a cohesive, working model of phylogenetic relationships, evolutionary trends and biogeographical histories, all of which are imperative to maximizing implementation of the impending genome sequence. Herein, we provide a succinct collection of data, information, and up-to-date interpretations that span important concepts such as taxonomy, diagnostics, systematics, micro- and macroevolution, and biogeographical and biohistorical reconstruction of the genus Trichinella. It is hoped that this information will provide fundamental knowledge to those working with parasites of this genus, as well as to those who see a more holistic value to the use of these organisms in their research.