Distribution of the Trichinela sp. in the naturally infected sables (Martes zibellina).

The sable (Martes zibellina) is a wildlife reservoir for Trichinella spp. in Siberian forest ecosystems, but age-related patterns of larval distribution, sex ratio, and encapsulation status remain poorly characterized. We examined 100 sable carcasses collected during the 2025-2026 hunting season in the Ulan-Ude forest region (Buryatia, Russia). Animals were classified as juvenile, subadult, or adult based on tooth wear and body weight. Trichinella larvae were recovered from diaphragm, masseter, and temporal muscles by artificial digestion. Overall prevalence was 14.0% (95% CI: 8.5-22.1%) and increased significantly with age: 5.3% in juveniles, 13.6% in subadults, and 33.3% in adults (trend p = 0.009). The diaphragm was positive in all infected animals. Temporal muscle involvement occurred only in subadults and adults (p = 0.037). The overall female-to-male larval sex ratio was 1.32:1, deviating significantly from 1:1 (p = 0.008), and was most female-biased in adults (1.57:1). Encapsulated larvae predominated in diaphragm (89.3%) and masseter (80.0%), while temporal muscles contained a higher proportion of non-encapsulated forms (41.7%). A logistic regression model based on age class predicted increasing probability of infection from 5.3% in juveniles to 33.3% in adults (adult OR = 7.8, 95% CI: 1.5-51.2). These findings indicate that age influences infection probability and larval distribution, with non-encapsulated forms predominating in temporal muscles of older animals, consistent with sequential muscle colonization.