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The collection materials of proboscis worms from fishes living in different types of Krasnoyarsk Region's water bodies (rivers, lakes, reservoirs) have been studied. Taxonomic features were identified, which made it possible to establish the species identity of acanthocephalans of Neoechinorhynchus from basins of the Yenisei, the Pyasina and the Khatanga rivers. Four species of this genus were recorded in water bodies of Krasnoyarsk Region. Neoechinorhynchus salmonis and N. baueri were identified in the collected materials from lower reaches of the Yenisei and Khatanga rivers, and N. tumidus were identified in the collected materials from the Putorana Plateau's lakes and Kureika reservoir. In addition, Neoechinorhynchus sp. individuals were found in roach Rutilus rutilus lacustris (Pallas) from Khabalyk lake (the Eastern Sayan Mountains). Additional sampling in this lake will help to determine this species. The article presents morphometric characteristics of the listed species of proboscis worms; information on their occurrence and abundance in the studied water bodies is also presented.

In the natural foci of the Siberian plague, the main vectors of the pathogen are two subspecies of Citellophilus tesquorum (Wagner, 1898): in Transbaikalia - C. t. sungaris Jordan, 1929; in Tuva - C. t. altaicus Ioff, 1936. The possibility of their reciprocal hybridization has been experimentally established. The time of F1 larvae appearance, the minimum period of metamorphosis and the number of ovarioles in female hybrids varied approximately within the same limits as in the parent subspecies. However, the number of offspring per adult female in F1 and F2 hybrids was ten times less than in the original forms. The study of the imago hybrids morphology based on traits that have no taxonomic significance showed that the level of their phenotypic similarity with each of the subspecies corresponded to the value of this indicator for individuals from natural populations and was significantly higher than the similarity of the two subspecies. An increase in body size was revealed in F1, which is leveled in F2. In experiments on infection of imago hybrids with the causative agent of plague, the formation of proventriculus "blocks" and the transfer of the microbe to laboratory animals were recorded, with higher efficiency than in the original forms.

Taxonomic diversity, characters of distribution and host-parasite relations of fleas of the genus Xenopsylla (Pulicidae) are analyzed. It is demonstrated that six species and two subspecies of fleas of the genus Xenopsylla, parasitizing on gerbils in the territory of Russia and adjacent countries are known as the main, secondary, or occasional vectors of the plague.

During epizootological examination of the Popov Island (Primorsky Territory) in May 23-25, 2022, four species of hard ticks were recorded by collection from vegetation: Ixodes pavlovskyi pavlovskyi Pomerantsev, 1946 (77.5% of the total all individuals), Ixodes persulcatus Schulze, 1930 (15.3%), Haemaphysalis concinna Koch, 1844 (4.5%), and Haemaphysalis japonica douglasi Nuttall et Warburton, 1915 (2.7%). A total of 651 tick specimens were collected. In previous years (1982 and 2014), these four species of ixodid ticks were also recorded here. In the territory of the island ticks are distributed unevenly. A local site was revealed (Cape Likander), where the abundance of ixodid ticks reached 100 individuals per hour. In an individual study of 387 ticks of four species by PCR, the RNA / DNA of pathogens were detected only among 346 individuals from the genus Ixodes. Tick-borne encephalitis virus was registered in 0.9 ± 0.50% of ticks, Borrelia - in 37.0 ± 2.60%, causative agents of human monocytic ehrlichiosis - in 9.0 ± 1.54%, causative agents of human anaplasmosis - in 7.2 ± 1.39% of ixodids. Observed values of the population density of hard ticks and their infection with pathogens do not allow classifying the territory of the Popov Island as epidemiologically low-risk area; therefore, a complex of preventive measures is required.

Summary is absent.