First report of Trichinella chanchalensis, and detection of foreign Trichinella spiralis, in wildlife in Alaska.

backgroundMembers of the genus Trichinella are muscle-dwelling zoonotic parasites of global importance for public health, animal husbandry, and trade. Trichinella chanchalensis (T13) is the newest species in the genus, first described in the Yukon and the Northwest Territories, for which the geographical distribution remains unknown due to limitations of the gold standard test for genotyping (multiplex polymerase chain reaction [PCR]). Our primary objective was to determine whether T. chanchalensis was present in Alaska, using a new molecular method that enables the description of the prevalence, co-infection, host associations, and risk factors for Trichinella spp. infection in wild carnivores.

methodsTrichinella spp. larvae were recovered through artificial digestion of muscle and genotyped using next-generation sequencing (NGS).

resultsTrichinella spp. larvae were detected in 53/157 (34%) animals, namely wolverines (Gulo gulo), arctic foxes (Vulpes lagopus), red foxes (Vulpes vulpes), coyotes (Canis latrans), wolves (Canis lupus), brown bears (Ursus arctos), and polar bears (Ursus maritimus), but not in black bears (Ursus americanus) or lynx (Lynx canadensis). Prevalence was highest in polar bears and wolverines, while intensity (larvae per gram, LPG) was highest in red foxes, arctic foxes, and wolves. Most animals (65%) harbored single infections with Trichinella nativa, followed by mixed infections of T. nativa and Trichinella T6 (33%). A single wolverine was infected with T. nativa, T6, and T. chanchalensis. Combining NGS with statistical methods, we found no evidence of competition between T. nativa and T6 in host muscles. Trichinella spp. infection (primarily T. nativa) was the highest in the Northwestern region, whereas T6 infection probability was higher in the Interior and Southern regions, suggesting differences in environmental resistance even among these three taxa. In a single, highly infected brown bear, we detected a rare case of Trichinella spiralis of foreign origin based on whole-genome sequencing, suggesting illegal importation and disposal of meat.

conclusionsWe report a new geographical record for T. chanchalensis and a rare finding of T. spiralis in North American wildlife, and demonstrate the utility of new NGS methods for describing the ecology of parasites maintained in wildlife hosts commonly presenting as co-infections.