Parazitologiia最新文献

Results of special parasitological dissections of roach samples from catches with the same fishing gear and at the same station (Monakhovo Cove, Chivyrkui Bay of the Lake Baikal) and at the same time in different years (1998-2002) are given. Stability of age-related dynamics of roach infection rate with Ligula intestinalisis in different years with the maximum of prevalence and mean abundance in fish of 3+ age, and the following sharp decrease in these rates in elder age groups, was revealed. Basing on prevalence decreasing of a single roach generation, the rate of fish mortality during its growth from age group 3+ to 4+ was estimated as 15.9-20.7%.

The opisthorchiasis caused by Opisthorchis felineus, the Siberian liver fluke remains a serious public health problem in Russia and Eastern Europe. Proteomic identification of the proteins in the excretory-secretory products (ESPs) released by O. felineus is an important key for the investigation of host-parasite interactions and understanding the mechanisms involved in parasite survival within the host. In the ESP of O. felineus we have identified 37 proteins using high-resolution proteomics approach (LTQ-FT-ICR mass spectrometer). The O. felineus secretes either excretes a complex mixture of proteins including: glycolytic enzymes (enolase, aldolase, fructose-1 ,6-bisphosphatase and other); detoxification proteins (4 isoform of glutathione S-transferases, Cu/Zn superoxide dismutase, thioredoxin peroxidase, thioredoxin); cytoskeletal proteins (beta tubulin and paramyosin); a number of proteases (cathepsin F, B1, leucin aminopeptidase 2); protease inhibitors (putative cys1 protein, leukocyte elastase inhibitor), binding proteins (ferritin, myoglobin, FABP) and other. In the O. felineus ESP we also identified Of-HDM protein belonging to a novel family "helminth defence molecules" (HDMs). The O. felineus proteins identified in this study provide necessary information for the further investigation of molecular mechanisms of opisthorchiasis pathogenesis and some of them would be of interest as potential antigens for vaccine and immunodiagnostics development and as potential new anthelmintic drug targets.

The full nucleotide sequences of DNA ribosome cluster of Leucochloridium paradoxum Carus, 1835 and L. perturbatum Pojmanska, 1967 were obtained. rDNA was extracted from 40 isolates of Leucochloridium sp. and analyzed using specific primers. The intraspecific genetically identity of morphologically detected L. paradoxum and L. perturbatum sporocysts was proven. A noticeable interspecific divergence between L. paradoxum and L. perturbatum was indicated. Using rDNA genotyping a case of double infection of snail Succinea sp. with L. paradoxum and L. perturbatum sporocysts was detected.

Stable isotope ratios of carbon (13C/12C, δ13C) and nitrogen (15N/14N, δ15N) in snail-host tissue (the foot and hepatopancreas) and trematode parasites on two stages of their life cycle were analyzed. Trophic structure in co-occurring trematode larvae was examined in the following species: five species of cercariae (Echinoparyphium recurvatum, Hypodereum conoideum, Plagiorchis mutationis, Diplostomum chromatophorum and D. volvens) and two species of metacercariae (Cotylurus cornutus and Echinoparyphium recurvatum) within two closely related snail hosts Lymnaea stagnalis and L. tumida using stable isotope analyses. Snail and parasite sampling was conducted in a riverine portion of the Kargat River of the Lake Chany basin, in the south of Western Siberia (54 degrees 37'76"N, 78 degrees 13'07" E), in August 2009. Four out of five studied cercariae species were depleted in 15N as well as in 13C relatively to snail hosts tissues (foot and hepatopancreas), supporting our previously published data for Plagiorchis mutationis and Echinoparyphium recurvatum cercariae. Such fractionation of cercariae is untypical of the commonly observed relationship between consumers and their food. D. chromatophorum cercariae had demonstrated an insufficient enrichment in δ15N volume in relation to the hepatopancreas. Both two species of metacercariae (C. cornutus and E. recurvatum) showed a significant enrichment in δ15N volume relatively to the host tissue consumed (fractionation values ranging from 1.5 to 4 per thousand depending on the species). The differences in δ15N and δ13C volume between cercariae and metacercariae observed in this study illustrate the complexity of the host--parasite trophic relationships. Such isotopic differences between cercariae and metacercariae can probably be explained by selective consumption of specific amino acids or lipids or by changes in metabolism associated with the life cycle of the parasite. The present study represents the first comparative analysis of trophic relationships between the host and the endoparasite at different life cycle stages. It demonstrates the potency of the stable isotope analyses for understanding trophic relationships in multispecies parasite communities.

Morphogenesis of the true ascocercus (euascocercus or euascocysticercoid) was studied in Schistotaenia srivastavai, a relatively rare parasite of the Red-necked Grebe Podiceps griseigena, and of intermediate hosts, damselfy and dragonfly larvae, in the Okhotsk-Kolyma region. Stages of postembryonic development were reconstructed by the material from spontaneously infected dragonflies' larvae, which corresponded to the published data on the development of metacestodes from the genus Tatria s. l. studied by Mrazek (1927) and Rees (1973). The euascocercus is the most widespread morphological modification of ascocysticercoids among Schistotaeniidae. According to Gulyaev (1989) and our data, the species of the family (the genus Mircia) have also a polycephalic modification of the ascocercus, or the multicercus. It represents a maternal individual that is filled with numerous small filial cysticercoids during the postembryonic development. These cysticercoids are formed of individual buds in the outer wall; later on, they are gemmated into the primary cavity of the maternal individual. Consequently, each daughter individual possesses its own single-layer exocyst, homological to the inner layer of the two-layered exocyst of the other ascocerci. Supposedly, exocyst's outer layer of monocephalic ascocerci is homologous to the outer wall of multicercus' maternal individual. Finally, diagnostic features of the third modification of ascocerci, namely megalocercus, described in the uniquely large metacestode Dioecocestus asper, corresponds to the characteristic of the metacestode Schistotaenia tenuicirrus, studied by Boertje (1975). S. tenuicirrus differs from D. asper in the spiral configuration formed on the entire surface of the endocyst (in D. asper, only on its dorsal side), and in a low number of proglottids in the larval strobile (D. asper possesses a multisegmental strobile). The reason, why so large protective envelopes (exo- and endocysts) develop in S. tenuicirrus with relatively small size of prospective body, remains unclear. Thus, life cycles of Schistotaeniidae represent all three modifications of the ascocerci: the true ascocercus (Shistotaenia, Tatria, Ryjikovilepis, Joyeuxilepis), the multicercus (genus Mircia), and the megalocercus (S. tenuicirrus).

The megalocercus of Dioecocestus asper (Mehlis 1831) from the haemocoele of dragonfly larvae possesses two envelopes: outer (exocyst) and inner (endocyst) ones. The exocyst contains the large endocyst and larval strobila with scolex attached to the latter. Outer and inner surfaces of these envelopes are organized as the tegument and have some structural differences. The exocyst is covered with slender microvilli. Its outer tegument contains numerous mitochondria; the inner one is filled with lipid droplets released into the exocyst's cavity. The well-developed protonephridial (excretory) system consisting of flame cells, collecting ducts and canals is the unique feature of the exocyst, noted for the first time. Thick (more, then 50 microm) distal cytoplasm of the outer tegument of the endocyst is the place of accumulation of uniform globules looking like a hyaloid layer. This outer layer together with underlying fibrous layer (up to 20 microm), apparently, protect the scolex and larval strobila during the transfer through feather clump in the stomach of grebes, definitive hosts of D. asper. Muscle cells of both envelopes retain their synthetic activity even in the fully developed metacestode. Probably, they are the main structural element, which produces fibers of the extracellular matrix and maintains the integrity of protective envelopes of the megalocercus.

Helminth species composition and infection rates of the Siberian tree frog Rana amurensis in Western Siberia were studied. Four species of helminthes--nematodes Rhabdias bufonis, Oswaldocruzia filiformis, Cosmocerca ornata and the trematode Haplometra cylindracea were found. Prevalence of helminths in the Siberian tree frog is 100%, and mean abundance is 27.5 +/- 4.8. Helminth species richness in the Siberian tree frog in the western periphery of their distribution area is lower than in the center of the range, in Yakutia and Transbaikalia, and is approximately equal to that in the northeastern boundary of the range, in Magadan Province. R. bufonis, a highly pathogenic nematode species, dominates in prevalence and abundance in the Siberian tree frog in Western Siberia as well as in other parts of the geographical range of this species.

Results of the study of fleas (Siphonaptera) collected from small mammals (insectivores and rodents) in the Russian Far East (Magadan Province, and Khabarovsk and Kamchatka Territories) are represented. Fourteen flea species were revealed in 17 species of small mammals.

Examination of river basins of Yakutia and the study of the previously collected material resulted in revealing of 34 species of the subfamily Prosimuliinae belonging to 8 genera (Gymnopais, Prosimulium, Helodon, Stegopterna, Greniera, Cnephia, Metacnephia, and Sulcicnephia). The fauna of Yakutia was supplemented with two black fly species Cnephia angarensis Rubzov, 1956 and Gymnopais frontatus Yankovsky, 1982. The distribution of the species Prosimulium tridentatum, Helodon alpestris, H. irkutensis, H. rubicundus, Stegopterna asema, and Cnephia lyra) was clarified. The combined table of species distribution with GPS coordinates of collecting sites has been composed.

The genetic diversity of the tick-borne encephalitis virus (TBEV) in the PCR-positive Taiga ticks collected in the Republic of Komi in 2010 was evaluated. The analyses of nucleotide sequences of the 5'-NCR fragments of viral genome from ticks had shown that 13 isolates of TBEV from 16 sequencing variants were represented by the highly pathogenic Far Eastern genotype of the TBEV and only 3 isolates were identified as the Siberian genotype of TBEV. The nucleotide sequences of 5'-NCR of viral genome strongly varied variable in individual ticks. Variability for the A1 element has been observed in all the tested samples, and for elements C1, B2, CS B--in more than 50%. A2 element and ATG codon of the 5'-NCR remained completely conservative. Computer simulation of conformations of the 5'-NCR of TBEV genome demonstrated the possibility of significant changes of the spatial structure of the 5'-NCR of viral genome in individual taiga ticks. The obtained data confirm the hypothesis that the variability in the 5'-NCR of TBEV genome can be crucial for efficient replication of TBEV in different hosts.