Toxocarosis - Toxocara canis induced infection in humans, especially in children. As the paratenic hosts of the parasite, it is attracting a lot of attention of physicians of different specialities, of epidemiologists and of immunologists. Toxocara canis was revealed in 4.1% of dogs and caged wild animals in the European part of the Russian North (Avdyukhina and Lysenko 1994). Sero-epidemiological survey accomplished in Russia in 1984-1989 showed 6% of seroprevalence with Toxocara antigen (ELISA) in the healthy children of the Irkutsk region and 7.3% in Tjumen city. The mean seroprevalence of toxocarosis was 1.7% in Tjumen city and 2.4% in the Jakutia Republic (Avdyukhina and Lysenko 1994). Irkutsk city is considered to be an endemic foci of toxocarosis. The infection was revealed in 29.5% of dogs there. Seroprevalence of toxocarosis was 6% in children and 2.6% in adults. Seroprevalence of infection in the other towns and in villages ranged from 2 to 11.5%. There was no difference in the prevalence of infection between the Russian and indigenous population (Evenki): 7 and 7.9%, respectively (Kuprijanova 1989). The titres were usually 1:6400 and higher in the clinically manifesting cases (Avdyukhina and Lysenko 1994). Sero-epidemiological survey of 465 children and teenagers and 382 adults made by the Martsinovski Institute in 1995-1996 revealed seroprevalence of toxocarosis of up to 14.1-15.4 in KPAD, in the Tomsk region, and in HMAD. Diagnostically significant titres (1:400) were up to 11.5% in HMAD and 42.4% in the Tomsk region (Table 6.2). In the Taimir Peninsula and in Chukotka, where adult aboriginals mostly were examined, sero-prevalence was about three-fold lower: 5 and 4.6%, respectively (Table 6.2). An additional examination of 20 children and 118 adults in the Khabarovsk region showed 18.8% of epidemiologically significant positive tests and 42.6% of them of diagnostic value (Report for the Federal Programme 'Children of the North' 1996). The specific IgG titres reached 1:400-800, in some cases - 1:1280-1:2560 in 17 patients of the Clinic of the Martsinovski Institute with toxocarosis clinically manifesting by lympadenopathy, hepatomegaly or/and pulmonary infiltration, by the blood eosinophilia up to 3 914-18 360 cells per millilitre (Ozeretskovskaya 1997b). The incidence of infection in Russia rose from 15 cases in 1991, to 641 (69.7% children) cases in 1999 mostly due to the wide serological screening of patients with allergic manifestations. The mean morbidity index in Russia was 0.8 in 2000, also, it reached 8.7 in the Udmurtia Republik, 7.6 in the Perm region, 5.2 in the EvenskAD (the Krasnoyarsk region), and 5.5 in the Sakhalin Island (Siskova et al. 2001).

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