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Three ecological forms of smelt have been analyzed: an anadromous (marine) form from the North Sea drainage basin and two freshwater forms — smelt proper from lakes Ladoga, Onego and Pyaozero, and dwarf (lake) smelt from lakes Beloye, Vozhe and Peipus (Pskov-Chudskoye). It is demonstrated that ecological forms of smelt feature their specific sets of parasites and the taxonomic structure of their diversity as represented by the composition of higher taxa. It is shown that ecological forms of smelt are characterized by a specific set of parasites and systematic structure of its diversity, which is assessed on the composition of the higher taxa. Most significant differences were detected between the anadromous form inhabiting waters of varying salinity and the freshwater form. These characteristics of the parasite fauna stem from smelt's high ecological plasticity, which enables the fish to inhabit both marine and fresh waters.

The fauna of the endobiotic intestinal ciliates from the European population of the antelope Saiga tatarica (Linnaeus, 1766) was studied. A comparative analysis of the available data on the species of ciliates has been carried out. It is shown that the species Polyplastron saigae can be considered one of the markers of the parasite fauna of the saiga western populations.

In the northwestern Leningrad Region of Russia, flagellates Angomonas deanei (Kinetoplastida: Trypanosomatidae) were found in the intestines of the fly Lucilia sp. (Diptera, Calliphoridae). Previously this species was not recorded from Russia. The flagellate identification was performed on the basis of comparative morphological research and phylogenetic analysis (sequence of the 18 S rRNA gene). Cultivation peculiarities of the new isolate A. deanei MN strain are being discussed.

Cestodes of the genus Passerilepis Spassky et Spasskaja, 1954 are known as widespread parasites of many bird species. However, life cycles of the majority of species of this genus in Western Siberia are poorly known. Material included in the present study allowed us refining the data on larval development of cestodes from the genus Passerilepis; furthermore, for some species of the genus intermediate hosts were revealed. In metacestodes of Passerilepis stylosa the process of fragmentation of the cercomer was discovered for the first time, which we consider as protective strategy of the parasite to avoid host's response reaction.

The analysis of the common periwinkle Littorina littorea L., 1758 cardiac activity under infestation of trematode parthenitas Himasthla elongata (Mehlis, 1831) was percormed. The differences in the heart function of infected mollusks included, on the first hand, a higher amplitude of plethysmograms, and, on the second hand, high-grade variance of heart rate. The positive inotropic effect of cardiac activity in infected L. littorea is discussed crom the point of view of the higher viscosity of the hemolymph. The second difference may point to trematodes as a stress-factor.

The setation variability was studied for the postpronotal, prespiracular, prealar, upper and lower mesepisternal, and upper and lower mesepimeral setae in several species of the genera Anopheles Meigen, 1818, Uranotaenia Lynch Arribalzaga, 1891; Culiseta Felt, 1904; Coquillettidia Dyar, 1905, Culex Linnaeus, 1758, and Lutzia Theobald, 1903. The new traits which allow to distinguish the species by setation were found. Among them are the presence of prespiracular setae in Anopheles claviger, a single postpronotal, prealar, prespiracular, and the lower mesepimeral seta in Uranotaenia unguiculata. Moreover, significant differences in the number of setae were revealed in many comparisons between several species, but, in most cases, with the notable overlap. We also found considerable differences between sexes in the number of the upper mesepimeral setae in Coquillettidia richiardii, Culex modestus, Culex hortensis, and Culiseta alaskaensis indica, and the postpronotal setae in Culex theileri. Predominantly left-lateralized distribution of the postpronotal setae has been identified for Coquillettidia richiardii and predominantly left-lateralized distribution of the lower mesepisternal setae has been detected for Culex modestus (taking into account the magnitude of bias, the leftward asymmetry on the species level was confirmed statistically with p < 0.05).

Species composition, seasonal dynamics, and a load of ectoparasites per individual and population of the pygmy shrew Sorex minutus have been examined in coniferous and mixed forests of the Novgorod Province during the period 1999—2003. Trapping of mammals was carried monthly, with exception of few accidental gaps. The Gero traps were used for catching micromammalian hosts. The lines of trap were checked 2 times a day, places of lines changed each 3—5 day. Total number of micromammalians collected during the period of study is 3215, including 265 specimens of the pygmy shrew S. minutus. Parasite fauna on the pygmy shrew included 13 ectoparasite species: fleas — 8, ixodid ticks — 2, gamasid mites — 1, and myobiid mites — 2 species. Species composition, occurrence and abundance indices of parasites changed during the year. In total, about 55% shrew specimens are infected with ectoparasites. The infracommunity of ectoparasites on the pygmy shrew usually consists of 1—4 species. Mean number of all ectoparasite individuals per one host specimens varies from 3.8 to 18. The greatest number of parasites (440 and 190) was collected from the shrews, which carried 1 and 2 parasites species, respectively. Biodiversity of parasite species in the ectoparasite community on the pygmy shrew and the load of parasites per one host specimen are lower than those in the common shrew and bank vole. The most numerous ectoparasite on S. minutus was Ixodes trianguliceps.

This article provides information about parasites of rearing fish in cage farms in the european part of Russia, surveyed in the period from 1996 to 2016. The fauna of parasites of cage fish comprised 52 species of parasites, including 27, 9, 5, 3, 1, 1, 1, and 5 species of protosoans, monogeneas, cestodes, trematodes, nematodes, annelids, clams, and crustaceans. Most of them are reprezented by species with a wide host range possessing the direct development cycle. Conditions leading to parasitic diseases offish developing in cages are discussed. Parasites that cause the death of fish in cages include the following species: Sphaerospora renicola (carp), Myxobolus dogieli (carp), Capriniana piscium (rainbow trout), Ambiphrya ameiuri (channel catfish), Dactylogyrus vastator (carp), Gyrodactylus truttae (salmon), Proteocephalus exiguus (rainbow trout), Ergasilus sieboldi (whitefish).

An atypical localization of Ligula intestinalis (Linnaeus, 1758) plerocercoids in muscles of the roach Rutilus rutilus lacustris (Pallas, 1814) from Kureika reservoir (the Kureika River is a tributary of the Yenisey River, Kara Sea basin) is described for the first time.

The present communication provides an overview of scientific reports, represented at the twentieth conference of the European Society for Vector Ecology, concerning the biology of arthropods — vectors of infectious agents, and methods of controlling their populations. The most urgent problems related to vector control and the development of unified methods for their eradication were discussed at the conference.