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Title: Genetic evidence of interspecies introgression of mitochondrial genomes between Trichinella spiralis and Trichinella britovi under natural conditions

Author
item FRANSSEN, FRITS - National Institute For Public Health And The Environment (RIVM)
item BILSKA-ZAJAC, EWA - National Veterinary Research Institute
item DEKSNE, GUNITA - Institute Of Food Safety, Animal Health And Environment-Bior
item SPRONG, HEIN - National Institute For Public Health And The Environment (RIVM)
item POZIO, EDOARDO - Istituto Superiore Di Sanità
item ROZYCKI, MIREK - National Veterinary Research Institute
item Rosenthal, Benjamin
item VAN DER GIESSEN, JOKE - National Institute For Public Health And The Environment (RIVM)

Submitted to: Infection, Genetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2015
Publication Date: 12/1/2015
Citation: Franssen, F., Bilska-Zajac, E., Deksne, G., Sprong, H., Pozio, E., Rozycki, M., Rosenthal, B.M., Van Der Giessen, J. 2015. Genetic evidence of interspecies introgression of mitochondrial genomes between Trichinella spiralis and Trichinella britovi under natural conditions. Infection, Genetics and Evolution. 36:323-332. doi: 10.1016/j.meegid.2015.10.005.

Interpretive Summary: Trichinellosis is a zoonotic disease caused by Trichinella larvae through ingestion of raw or undercooked meat. To date, 12 morphologically indistinguishable taxa are recognized in this genus, and the extent of interbreeding among them remains unclear. This study aimed to examine the potential and actual interbreeding between two such species, one of which (T. spiralis) is the major source of human infection via infected pork and the other of which (T. britovi) is frequently found in wild carnivores in Europe. Natural hybrids were detected through multi-locus genetic sequencing, and laboratory experiments confirmed that fertile hybrids do result when males of one species are given no choice but to breed with females of the other; such pairings, however, result in far fewer offspring than would otherwise occur. These data will interest epidemiologists, parasitologists, and food safety regulators as they enhance our understanding of the degree of connection between cycles of transmission in wildlife and domesticated swine.

Technical Abstract: Trichinellosis is a zoonotic disease caused by Trichinella larvae through ingestion of raw or undercooked meat. To date, 12 morphologically indistinguishable taxa are recognized in this genus, of which four are circulating in Europe (Trichinella spiralis, Trichinella nativa, Trichinella britovi and Trichinella pseudospiralis). T. spiralis and T. britovi occur simultaneously in north- eastern European wildlife. Few researchers however, have addressed the possibility of hybrid formation between T. britovi and T. spiralis. So far, results of experimental hybridisation attempts between T. britovi and T. spiralis are rather inconclusive. The aim of the present study was to evaluate occurrence of hybridisation events under natural conditions. We studied molecular polymorphisms of single T. spiralis and T. britovi muscle larvae (ML) from natural infections based on nuclear 5S rDNA and mitochondrial cytochrome c oxidase 1 (CO1) gene sequences. Sequence analysis of 89 individual T. britovi ML from Latvia and Poland revealed 6 haplotypes of the 5S ribosomal RNA intergenic region (5S rDNA) and 14 of cytochrome c oxidase 1 (CO1) gene. In contrast, only two haplotypes were observed at both 5S rDNA and CO1 of 57 individual T. spiralis ML from Polish wild boar and red foxes. More importantly, this study demonstrates hybridisation in eight individual ML between T. britovi and T. spiralis under natural conditions in Polish wild boar and red fox, revealed by combining 5S rDNA and CO1 sequence information of individual Trichinella ML.