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In the taiga of the region in question at the latitude 56°N the photoperiod regimens of 25 June and 21 July determine 50% diapause in engorged larvae and nymphs of Ixodes persulcatus. The durations of the day time on these dates are 17 h 34 min and 16 h 45 min respectively. Seasonal fluctuations of temperature and precipitation in May-June are the main reasons for the modification of the critical photoperiod. In some years the critical dates for larvae and1, nymphs vary under these factors within the limits 11-28 July and 19 June-6 July respectively. The critical durations of the day time for these date limits are 16 h 20 min-17 h 12 min and 17 h 23 min-17 h 37 min respectively.

It is proved that in the tick fluid saliva and in the cement plug produced by Rhipucephalus appendiculatus there are bactericidal substances very similar in their activity to the egg lysozyme. The possible role in the transmission and conservation of the specific tick-borne, insensitive to the lysozyme pathogens such as rickettsiae, tick-borne encephalites virus and borreliae (pathogen of Lyme disease) is discussed. It is supposed, that bactericidal substances in the cement plug protect accumulated in it the tick-borne pathogens (TBE virus, borreliae) from the compete and destructive influence of the vulgar, mainly coccal microflorae and from the purulent inflammation, which hinders not only tick feeding but probably specific tick-borne pathogens spreading in the vertebrate host.

The new mathematical model of P. falciparum malaria has been created. One means the operational forecast of epidemic process when different control measures are realized. The original modelling methodology for epidemics is used. The proposed methodology is allowed to take into account the natural variety of model's parameters. The malaria model consists of the unlinear integro-differential in partial derivatives combined equations including individual and population characteristics. The informatics technologies permits to see information about model and its groundes. The model's verification has been done on data of Garki-project.

The parasitological analysis in 12 populations of littoral snails of the genera Hydrobia and Littorina was carried out. The difference of infection rate in males and females of snails is recovered in some cases. The monitoring of heavy infected populations of Littorina saxatilis and L. obtusata during 8 years gave the possibility to observe the dynamics of parasite distribution in different age groups of hosts. The distribution of the most numerous trematode Microphallus piriformes in males and females of snails is different. The discussion on the biological sense of the parasite's strategy in relatonships with heterosexual specimens of host is based on the data on the reproductive structure of the host populations.

The great structural diversity in the cestodes Glandicephalus antarcticus (Baird, 1853) from the stomac and intestine of the Ross Seal and G. pefoliatus (Railiet et Henry, 1912) from the bile-pancreatic duct of the Weddel Seal was recovered. These two cestodes are moved out of the family Diphyllobothriidae Lühe, 1910 and considered as the new family Glandocephalidae fam. n. within the superfamily Diphyllobothrioidea. Redescriptions of both species, and some indices of invasion rate are provided.

540 male Golden Hamsters were divided into 3 groups: I - free from invasion, II - once infected, III - repeatedly infected. Diurnal activity of portal lymph node immunocompetent cells was investigated in spring, autumn and winter at 3, 7, 11 a. m. and 3, 7, 11 p. m. Peculiarities of diurnal immunocompetent cell activity at on acute opisthorchiasis stage, depending upon a season invasion frequency is determined by immunoreactivity level. Eosinophilic and lymphocytic reactions and the ratio of mitotic activity to degenerative elements are the lymph-node immunocompetence indices.

The Waldman e. a. (1986) method of separation of Cryptosporidium spp. oocysts from feces by using a percoll discontinuous density gradient appeared a method of choice for obtaining large numbers of oocysts of C. parvum free of fecal contamination. Feces of 7-12 day old calves, spontaneously infected with C. parvum, were concentrated and purified by the above technique. The purified oocysts were shown to be infectious by inoculation of 6-9 day old rats with an average dose of 20000 oocysts per animal. The rats shed oocysts after 4 days. At necropsy on day 4 postinoculation, the pattern of endogenous development appeared normal, when examined on frozen sections of fresh tissue, using the Bright cryostat, stained with hematoxylin and eosin. Samples of the clean sediment, presumably containing only oocyts of C. parvum, were smeared and stained with carbol fuchsin after Ziehl-Neelsen, and with gentian violet after Sidorenko (1988). With the latter technique, an intense gentian violet staining screened all the constituents of the smear, except the oocysts, which being "negatively stained" looked as small transparent spheres 4-5 mkm in diameter. But of special interest was the reaction of the smeared organisms with carbol fuchsin. Some organisms stained dark red and had a variable number of dark granules, seemingly on the surface; whereas others stained light reddish, if at all, and appeared as transparent spheres. It does not seem unlikely that the sediment, resulting from the final step of percoll separation, may contain, besides oocysts, some other endogenous stages (meronts, gamonts, thin-walled oocysts) that appeared in the lumen of the intestine because of an intense flow of diarrheal fluid during cryptosporidiosis. Unlike the thick walled oocysts, other endogenous stages are not covered with protective walls and thus fail to absorb acid fast staining. Segmented meronts were obviously observed on the rat fecal smears 96 hours after infection. This observation enables us to propose that newly infected hosts-recipients may obtain, with diarrheal fecal masses of infected donors, not only sporulated oocysts, but also some earlier developmental stages. Merozoites, released from the segmented meronts, could start in the intestine asexual rounds, thus shortening the resulting prepatent period. Fluctuations in prepatent period duration are characteristic of Cryptosporidium spp., and the above observation may be one of its explanations.

On the area of former USSR and Russia 10 species of Blastocystis were described: Blastocystis lessonae from Rana lessonae, B. anatis from Anas platyrhynchos, B. anseri from Anser anser, B. galli from Gallus gallus, B. numidae from Numida meleagris, B. meleagridis from Meleagris gallopavo, B. equi from Equus caballus, B. suis from Sus scrofa, B. bovis from Bos taurus, B. ovis from Ovis aries.

On the basis of electronmicroscopic data the description of Alfvenia ceriodaphniae sp. n. from Ceriodaphnia reticulata (Crustacea, Cladocera) is presented. The nuclear apparatus of meronts is diplokariotic. Sporonts, sporoblasts and spores are uninuclear. The sporogonial Plasmodium undertakes the rosette-like division with the formation of sporoblasts. Spores are egg-shaped, their size: 4.5(4.2-4.8) X 3.3(2.9-3.5) µm. Evry spore lays individually inside the envelope, that is formed from the external layer of the sporoblast wall. Polar tube is isofillar, forming 8-9 coils. Polaroplast is consisted of the lamellar and chamber parts. The site of parasite localisation is crustacean hypoderm.

A description of the population of the nematode Heterorhabditis bacteriophora recovered in different biotopes of the north zone of the Krasnodar area. Experiments have shown that this species is pathogenous to caterpillars of the moth Hyphantria cunea and larvae of the click beetle Agriotes ponticus.

The new trematode Neogogatea rauschi sp. n. is described from intestine of the White-tailed Sea Eagle Haliaetus albicilla from Khabarovsk area. It differs from other species of the genus by the extremely long bursa of the cirrus, by deep cave, and also by well developed genital sphinoter. An inproved diagnosis of the genus Neogogatea is given.

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Summary is absent.