Ecology of trichinellosis transmission in the Voronezh state nature reserve and adjacent areas, Russia.
The article considers certain aspects of the morphology and biology of Trichinella, and the ecology and epizootology of trichinellosis in the Voronezh State Nature Reserve and its adjacent areas (Black Soil Region of Russia). Original data were collected during 30 years (1990-2019) from potential hosts of Trichinella, mainly carnivorous mammals. During this period, more than 200 specimens of wild and domestic carnivores of three families (Canidae, Mustelidae, Felidae) were studied. Six species of wild carnivores (Canis lupus, Vulpes vulpes, Nyctereutes procyonoides, Meles meles, Martes martes, and M. foina) were obligatory hosts. In addition, Trichinella was found in Erinaceus concolor and two species of domestic carnivores (Canis lupus familiaris and Felis catus). The highest prevalence of infection was observed in Vulpes vulpes, Nyctereutes procyonoides, Meles meles, and Martes martes (35.7-70.0%). These hosts play a leading role in the natural trichinellosis transmission. The carnivores can be divided into two groups according to the intensity of infection by Trichinella larvae per gram of muscles (lpg). The first group includes native carnivore species (Vulpes vulpes, Canis lupus, Meles meles, Martes martes, and M. foina), with an average of 10 lpg. The second group includes introduced species (Nyctereutes procyonoides) and invasive species (immigrants) from anthropogenic areas (Felis catus), with an average of 700 lpg. Due to its high pathogenicity, Trichinella can be considered as a significant factor in regulating the number of alien carnivorous species. Trichinella is also characterised by aggregated distribution in the muscles. In the Voronezh State Nature Reserve, the highest lpg values were observed in the muscles of the front and rear limbs of the carnivores. Over 50% of the local hemipopulation of Trichinella is concentrated in these muscle types. Based on the assessment of the morphological features of the Trichinella capsules and larvae from carnivores, two clusters of T. nativa hosts were identified. These clusters comprise carnivorous species that have closer trophic relationships. The variability of quantitative and qualitative parameters in the hosts indirectly reflects the specifics of the relationships in the host-parasite system and shows nutritional preferences of the studied carnivores. In the Voronezh State Nature Reserve and its adjacent areas, Vulpes vulpes is the main link in the stable transmission of trichinellosis. Vulpes vulpes has high rates of infection intensity (35.7%) and large hemipopulations of Trichinella larvae (3.3 million specimens). Vulpes vulpes is the most abundant carnivorous species in the Voronezh State Nature Reserve and the most common hunting prey. So it can be used for monitoring the trichinellosis in European Russia. In the Voronezh State Nature Reserve, invertebrate animals can also contribute to the trichinellosis transmission. Carabid beetles (Carabidae) were registered as the disseminators of T. nativa. At present, in the Voronezh State Nature Reserve and in its adjacent areas, trichinellosis is transmitted by wild carnivores. The dominant position in the parasitic system of T. nativa is occupied by Vulpes vulpes. The other Carnivora species are subdominant. The specifics of the trichinellosis transmission and Trichinella transmission factors depend on the trophic relationships between animal hosts. The main forms of trophic relationships between carnivores are predation, necrophagy and cannibalism. Erinaceus concolor and insects (Carabidae) may also contribute to the preservation and dissemination of Trichinella.