Diphyllobothriasis had been registered from the 1930s through all territory of the Russian North from the Kolsky peninsula and Karelia in the West, to the Jamal peninsula, JNAD and HMAD in the West Siberia, the Krasnoyarsk region, Yakutia, Kamchatka, Sakhalin, and the Magadan region in the east. The higher prevalence of infection was revealed close to food-land served by water reservoirs than along coasts of large rivers. The prevalence of infection in the indigenous population of the littoral zone of the

Enisei River in the 1930s had reached 52%. In the early 1960s it varied there from 1.4 to 19.2%. In the foci of the Kolsky peninsula, the prevalence of the infection by the same time was reduced from 23.7 to 1.53% (Shikhobalova et al. 1969). New foci of diphyllobothriases have been formed after the building of water reservoirs with hydro-energy complexes, in particular the one in Krasnoyarsk (Klebanovskii 1985). The morbidity rate per 100 000 population for diphillobothriasis in the USSR in 1987 was 13.1 (Sergiev 1993).

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The main incidence of diphyllobothriases in man in Russia is due to D. latum infestation with synanthropic foci (Klebanovski 1980, 1985). The intermediate hosts are Copepoda (Crustacea) and freshwater fish - pike, perch, salmon, trouts, and eel. Even in sparsely populated regions of Siberia, such as Karim lakes system in the western riverside of the Konda (HMAD), plerocercoid larvae were found in 92% of pikes in lakes that were close to villages and in 7.1% of pikes in lakes practically not visited by man (Klebanovskii 1985). Synanthropic foci of D. latum infection are the most intensive in the middle and middle-lower reaches of the West and the East Siberia great rivers (but in the lower reaches of the Irtish river) (Klebanovskii 1985). The prevalence of D. latum infection in the population of middle reaches of the Ob river in the 1970s was 10%. In aboriginal populations (Komi, Hanti) of the Ob middle-lower reaches it was 43.6% and was only 25-7% in the lowest reaches of the river (Klebanovskii 1985). In the middle zone of the Krasnoyarsk water reservoir, the prevalence of D. latum infection in 1985 reached 11.7%; in 1-2-year-old children it was 4% in 1984 and 12.7% in 1985 (Plyuscheva et al. 1987). Diphyllobothrium dendriticum is the causative agent of 'seagull's diphyllobothriasis'. The disease takes second place in incidence of diphyllobothriases in man (Klebanovskii 1980, 1985). The first intermediate host - E. gracilis, the second ones - Coregonuspeled, C. lavaretuspidshian, C. muksun, and Thimallus arcticus. The definitive hosts are gulls, magpies, and crows. The high incidence of D. dendriticum infection in the aboriginals of the Taimir permits to consider that man served as the one of the (local) definitive hosts of the parasite. Diphyllobothrium dendriticum infection have been revealed in aboriginal population of Arctic zone of West and East Siberia, in Jakutia and Chykotka. In the indigenous population of the upper reaches of the Khatanga river (the Taimir peninsula) the prevalence of the infection was up to 11.8-23.5%, but in the lower reaches only 7-7.5% (Klebanovskii 1985). In the Sackha Republic (Yakutia) the prevalence of D. dendriticum infection in the middle-lower reaches of the Lena river was up to 6.6% in adults and 1% in children (Simonova 1995).

There are mixed - D. dendriticum and D. latum foci of diphyllobothriases in the Russian Arctic zone, where the former parasite makes about 5/6 of the incidence (Klebanovskii 1985). In 1991, the morbidity rate of diphyllobothriases in the Taimir peninsula was 2.36. The prevalence of diphyllobothriases in children of INAD was 19.7% (Khodakova et al. 1996). Diphillobothriasis (without species discrimination) was revealed in 12.9% of villagers and in 23.7% of reindeer-breeders in Chukotka (Lebedev et al. 1986). The zoonotic parasite D. ditremum in the Russian North is not socio-economically significant (an abortive course of infection) (Klebanovski 1985).

Diphyllobothrium klebanovskii revealed to be the main (if not the only) agent of the infection in humans in the northeast of Russia (Muratov and Posochov 1988). The main definitive host of D. klebanovskii is U. arctos (parasite was revealed in 16 out of 36 bears). Canidae, Felidae, and Mustelidae were infected for 1.7, 0.6, and 0.5%, respectively. Animals contracted the disease through consuming of Oncorhynchus gorbusha (humpbacked salmon), O. keta, and Hucho perrui. The prevalence of the infection in aboriginals in the North Pacific reaches 7.6% (Muratov 1993). Histological study of plerocercoids and adult worms of D. klebanovskii permitted to consider that it cannot be discriminated from D. nikonhainense, D. luxi, and D. giljacicum (Dovgalev et al. 1991). On the grounds of the priority of D. luxi description (Rutkevitch 1937), Dovgalev and Valovaja (1996) suggested to consider the latter as the main agent of diphyllobothriasis in the Pacific coast of the Russian Far East. The mean morbidity index of diphyllobothriasis in Russia was 15.7 (9.9 in children) in 1999, also reached 489.6

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in EvenkyAD, 382 in Yakutia, 304.6 in NenezkyAD and 247.7 in TaimirAD (Siskova et al. 2001).

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