Detection of RNA Markers of West Nile Virus in Zoological and Entomological Material from Various Regions of the European Part of Russia in 2021–2023

Relevance. In epidemiological surveillance of West Nile fever (WNF), infection of West Nile virus (WNV) in zoological and entomological material is an important indicator of the activity of the natural focus, which can be used to predict the development of the epidemiological situation, adjust the scope and timing of prophylactic and anti-epidemic measures. It is noteworthy that there were no positive findings or single detections of WNV markers in zoological and entomological material in most subjects of the European part of the Russia. Aims. To obtain estimated data on the intensity of the epizootic process of WNF in the territory of the European part of Russia. Materials and methods. Collection of zoological and entomological material of WNV in 2021-2023 was conducted in the territories of 32 entities of the Russian Federation in accordance with the current regulatory and methodological documents. Field material was analyzed by RT-PCR using the AmpliSense WNV-FL test system, and genotyping of samples positive for WNV RNA was performed using the Ampligen-WNV-genotype-1/2/4 test system. Results and Discussion. During the period 2021–2023, in the course of this study vertebrates were captured: 774 birds, 1126 small mammals, and 22 frogs; and arthropods were collected: 142600 bloodsucking mosquitoes, 33 bloodsuckers, 3070 midges, 14049 ixodid ticks, and 71 argas ticks. WNV RNA was detected in 9 out of 1922 studied vertebrate animals and in 112 out of 8047 pools of blood-sucking arthropods. The infection rate of blood-sucking mosquitoes was 0.07%, ixodid ticks – 0.09%, birds – 0.9%, frogs – 9.1%, which indicates that these animal groups are widely involved in the epizootic process. Markers of WNV in field material were detected in 14 entities. In 6 of them positive findings were obtained for the first time. WNV RNA of 1 genotype was detected in pools from the Central Federal District, 2 genotypes - in all surveyed districts, 4 genotypes - from the Southern Federal District. Conclusions. Active reconnaissance studies led to the expansion of our ideas about the existence of WNF foci in the European part of Russia. In populations of birds and blood-sucking arthropods in this area, WNV is steadily circulating. WNV-infected birds were found in the Southern Federal District and the Central Federal District, mosquitoes – in all surveyed federal districts, amphibians and ticks – only in the Southern Federal District