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Recent studies on the digenean fauna at the White and Barents Seas have shown that there are more species than previously thought. These data are emerging in a series of publications, and we suggest to summarize them in a form that is convenient for practical use. Here we provide a guide that covers the 11 species from the family Notocotylidae that we have recorded in the intertidal gastropods Ecrobia ventrosa, Peringia ulvae, Littorina spp. and Onoba aculeus. We recap brief descriptions of rediae and cercariae, documented host and geographic range, though for several species the information is incomplete. We also refer to the DNA barcodes from GenBank, including the new ones. For the better usability, we include hints on the mollusc identification and explain how to deal with the parasites (field and lab procedures).

Leucochloridium sp. Carus, 1835 sporocyst with a mature colored broodsac was found in the Boksitogorsk District of Leningrad Region (Russia) in Succinea putris L., 1758 snail. The pigmentation of the sporocyst's broodsac was shown to differ from ones of other Leucochloridium Carus, 1835 species, previously described for Europe. The obtained sporocyst is most similar by the coloration of its broodsac to the trematodes of the same genus from Japan. The genotyping of the investigated sporocyst by the rDNA (ITS1, ITS2, 5.8S complete and 18S и 28S partly sequences) gene fragments was conducted. Genetic distances between obtained sporocyst and previously described species of Leucochloridium genus are higher than intraspecific ones in the most cases. This data and data of morphological analysis can imply that the investigated sporocyst belongs to the separate species of Leucochloridium genus, previously not discovered in the European region.

The myxosporean Myxidium rhodei Leger, 1905 is a common parasite of Palearctic cyprinids. The parasite occurs predominantly in Bowman's capsules of the kidney of the common roach Rutilus rutilus. In 1999-2021, these fish were infested with M. rhodei at a high prevalence (94-100%) and intensity of invasion (up to 1578 pseudocysts). In this work, we analyzed the age-related, seasonal, long-term dynamics, and spatial distribution of the roach M. rhodei infestation in the Chivyrkuisky Bay of Lake Baikal. The parasite is primarily recorded in yearlings, then the intensity of M. rhodei roach invasion increases, reaching the maximum in middle-aged fish, and decreasing in older ones. M. rhodei has an annual developmental cycle in roach. Fluctuations in M. rhodei infestation of the studied fish during 25 years of observations correlate with long-term changes in the hydrological regime of Lake Baikal.

The article presents the results of our own research and a review of literature on the distribution and some ecological features that contribute to the maintenance of the canine babesiosis natural focus in the Kuznetsk-Salair mountains. Among all admissions of dog owners to the Kuzbass Station for the Control of Animal Diseases, the proportion of dogs diagnosed with babesiosis was 17%. During the period of the maximum rise, this diagnosis was true for every second dog. Among Dermacentor reticulatus ticks (the main vector of Babesia canis), the proportion infected with B. canis constituted about 12%. Among wild animals, B. canis was revealed in the blood of the Lepus timindus and the Alces alces. The boundaries of the distribution of D. reticulatus in the region corresponded to the boundaries of the forest-steppe, which, in turn, is increasing due to the reduction in the area of dark coniferous taiga forests due to excessive anthropogenic impact.

The Baikal tract is a highway, about 70 km long, connecting the city of Irkutsk with the Listvyanka village, located on the coast of Lake Baikal. There are heavy traffic and a significant recreational load with the location near the roadbed of many gardening, cottage settlements and tourist centers. The average number of taiga ticks for all years of observations in the vicinity of the tract was 27.4 ± 4.96 individuals per flag hour, with the maximum recorded abundance of 255 individuals per flag hour. In the vicinity of the road under consideration, the cores of taiga tick populations were identified - areas with a high and stable number of taiga ticks. In the spatial dynamics of the tick population, an increase in the average number and density of the taiga tick population with distance from the city was observed, which reaches maxima in the middle of the tract, and then decreases again when approaching the lake. Baikal. In the long-term dynamics of its abundance, one can note a change in the structure of the tick population starting from 2018. This was reflected in a decrease in the share of routes without ticks and an increase in the share of routes with an average and above average number of ticks. On the basis of the studies carried out, it can be fairly reasonably assumed that in the vicinity of the Baikal tract there are three populations of the taiga tick, characterized by the peculiarity of the spatial structure of abundance and its dynamics.