Hiding in plain sight: discovery and phylogeography of a cryptic species of Trichinella (Nematoda: Trichinellidae) in wolverine (Gulo gulo)

Authors: SHARMA, RAJNISH - University Of Saskatchewan; THOMPSON, PETER - Non ARS Employee; HOBERG, ERIC - University Of New Mexico; SCANDRETT, BRAD - Canadian Food Inspection Agency; KONESCI, KELLY - Canadian Food Inspection Agency; HARMS, N JANE - Government Of Yukon; KUKKA, PIIA - Government Of Yukon; JUNG, TOM - Government Of Yukon; ELKIN, BRETT - Government Of The Northwest Territories; MULDERS, ROBERT - Government Of The Northwest Territories; LARTER, NC - Government Of The Northwest Territories; BRANIGAN, MARSHA - Government Of The Northwest Territories; PONGRACZ, JODIE - Government Of The Northwest Territories; WAGNER, BRENT - University Of Saskatchewan; Rosenthal, Benjamin; JENKINS, EMILY - University Of Saskatchewan

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2020
Publication Date: 4/1/2020
Citation: Sharma, R., Thompson, P., Hoberg, E., Scandrett, B., Konesci, K., Harms, N., Kukka, P.M., Jung, T.S., Elkin, B., Mulders, R., Larter, N., Branigan, M., Pongracz, J., Wagner, B., Rosenthal, B.M., Jenkins, E. 2020. Hiding in plain sight: discovery and phylogeography of a cryptic species of Trichinella (Nematoda: Trichinellidae) in wolverine (Gulo gulo). International Journal for Parasitology. 50(4):277-287. https://doi.org/10.1016/j.ijpara.2020.01.003.
DOI: https://doi.org/10.1016/j.ijpara.2020.01.003

Interpretive Summary: A team of USDA and Canadian researchers monitoring wildlife infections were surprised to discover an entirely new species of Trichinella. Standard assays could, and probably have, confused this species for another that is common in the Canadian Arctic. Since other species in this genus sometimes cause foodborne illness when people consume undercooked food, it will be important to understand whether people can contract, or are already contracting, infection with this previously unknown species. This information will interest food safety authorities, wildlife biologists, parasitologists, and epidemiologists.

Technical Abstract: Trichinellosis is caused by nematodes of the genus Trichinella, which has two major clades. The encapsulated clade includes six species and three genotypes, whereas the non-encapsulated clade includes three species. In North America including Canada, five species of Trichinella (T. spiralis-T1, T. nativa- T2, T. pseudospiralis- T4, T. murrelli-T5 and Trichinella T6) have been found in homeothermic vertebrate hosts. Here we discuss the discovery, phylogeny, geography and host range of a previously unrecognized cryptic species of Trichinella designated as the T13 genotype. Phylogenetic analysis showed that a lineage containing T1 + T. nelsoni- T7 was the sister group for T13 and the remaining species in the subclade of encapsulated Trichinella (i.e T. patagoniensis-T12 T2, T6, T. britovi-T3, T8, T5, T9). A relatively basal position for T13 was unexpected and indicates a historically deep divergence, predating the later radiation of an assemblage of species distributed primarily across the Holarctic, Nearctic and Neotropical regionsOf 95 animals tested using PCR-RFLP, 68 were hosts for Trichinella nativa based on the mitochondrial genome of muscle larvae, 2 were hosts for Trichinella T6, and 11 had mixed infections of T. nativa and Trichinella T6. Specimens of a putative cryptic species of Trichinella were found only in wolverines, and 14 animals were infected either as single infection (11/14), or as mixed infections with T. nativa and Trichinella T6. Specimens designated as T13 occur in sympatry with Trichinella T6 and T. nativa geographically (Yukon, Northwest Territories) and can be observed in the same host (wolverine), although parasite species in this geographic assemblage are not closely related. Multiplex PCR used in the standard identification of Trichinella isolates has misidentified this putative cryptic species, directly confusing it with T. nativa. We recommend use of a newly developed PCR-RFLP or sequencing to confirm identification of the isolates of T. nativa or any species of Trichinella, respectively. Our results indicate that T13 is not geographically widespread in Canada, and may be limited to wolverine in Northwestern Canada, especially the Yukon, suggesting a possible historical link to Beringia and the Palearctic. Exploration of Alaskan and Siberian isolates may be contribute to further resolution of a geographically complex history for Trichinella and other parasites across the Western Hemisphere, Beringia and Eurasia.