[Seroepidemiologic characteristics of opisthorchiasis foci with various endemic levels].

Combined coprological (by an ether-formol method) and serological (by solid-phase enzyme immunoassay--EIA) screening of the population to detect opisthorchiasis was performed in the settlements situated in the Ob, Dnieper and Northern Dvina basins. Disease rate in the hyperendemic area on the Ob exceeded 80%, by the results of coprological population screening, while annual infestation rate established on the basis of specific antibodies determination in the blood was 70%. Infestation and disease rates in mesoendemic area, at the Ob tributary and in the Dnieper basin were practically equal and accounted for 30-40%. Infestation rates in hypoendemic areas of the Dnieper and Northern Dvina basins exceeded those of the disease rate. Causes of this phenomenon are discussed. Double serological screening of population in the foci performed in summer-autumn and spring seasons demonstrated a considerable increase in infestation rate parameters in autumn and their decrease in spring. Seasonal character of infestation is better expressed in the mesoendemic areas than in the hyperendemic ones. Infestation and disease rates are discussed for various age groups in different areas.