Pathogens of Zoonotic Viral Infections, Circulating in Populations of Small Mammals: an Overview of the Current State

Small mammals (rodents, insectivores, and bats) are the main reservoirs for a wide range of zoonotic viruses. These include the agents of vector-borne infections transmitted via bites of blood-sucking arthropods (ixodid ticks, mosquitoes, sand flies) and non-vector-borne infections (orthohantaviruses and others). Natural foci of viral infections, the reservoir of which are small mammals, are of primary epidemiological significance in the Russian Federation: hundreds of cases are recorded annually, many of which are severe. The aim of this review was to summarize current data on the circulation of viral zoonotic pathogens in small mammal populations in natural foci in the Russian Federation and worldwide, as well as to identify key issues in epizootiological surveillance and the study of reservoir relationships between hosts, pathogens, and vectors. It has been shown that among the zoonotic viruses circulating with the participation of rodents and insectivores, along with the most significant and widespread, returning (re-emerging) pathogens that pose a serious global and regional threat are also of great epidemiological importance. These are representatives of the Flaviviridae family (tick-borne encephalitis virus, Omsk hemorrhagic fever virus, Kyasanur forest disease virus), Bunyaviridae (orthohantaviruses, Crimean-Congo hemorrhagic fever virus, and others), and Coronaviridae families. It was noted that small mammals acted not only as reservoir hosts for viruses but also as feeders, ensuring the maintenance of populations of vectors (ixodid and argasid ticks, mosquitoes and midges), thereby creating stable parasitic systems. The issue of zoonotic viruses circulating among small mammals remains urgent for both the Russian Federation and the global community. Analysis of global trends indicates that infectious diseases of animals are expanding their range, thereat many of them with zoonotic potential. The key drivers of this process are climate change, expansion of international trade and transformation of ecosystems, requiring improved epidemiological monitoring and an interdisciplinary approach to risk assessment.