Experimental infection of immunosuppressed mice demonstrates freeze tolerance of Trichinella chanchalensis.

Trichinella chanchalensis (T13) remains poorly characterized, limiting understanding of its biology, freeze-tolerance, and zoonotic potential. One major challenge is that infective first-stage larvae can only be obtained from naturally exposed wildlife in northern North America, which often harbour co-infections with other Trichinella taxa. Therefore, we used next-generation sequencing (NGS) to identify naturally infected wolverines with high proportions of T13 larvae. We recovered larvae from muscle tissue previously frozen at -20 °C for up to 15 months and orally inoculated a total of 55 CD-1 and BALB/c mice, including immunocompetent and immunosuppressed groups, with doses of 21-581 larvae. Mouse carcasses were digested, and recovered larvae were genotyped using NGS. Establishment and recovery of T. chanchalensis larvae were consistently low, with only two larvae recovered from one BALB/c mouse in a pure infection and 2-913 larvae from immunosuppressed mice as mixed infections, despite good recovery of larvae of T. nativa and Trichinella T6. On repassaging in mice, only two T. chanchalensis larvae were recovered after the second passage. These results suggest poor adaptation of T. chanchalensis to laboratory mice, despite immunosuppression, and/or lower freeze-tolerance of T. chanchalensis compared to T. nativa and Trichinella T6. Differences in cold adaptation among northern Trichinella taxa likely reflect ecological and evolutionary pressures, with T. nativa considered the most freeze-tolerant, while T6 and T. chanchalensis exhibit comparatively lower tolerance. Understanding the biology and freeze-tolerance of T. chanchalensis is important for food safety and for developing One Health-informed surveillance to protect northern communities reliant on game meat.