[The mass treatment of opisthorchiasis with praziquantel from the viewpoints of the clinician and the epidemiologist].

About a 20-years period of chloxyl (hexaparaxylol) mass treatment of opisthorchiasis in hyper- and mesoendemic territories of Russia did not change the prevalence of the infection, reducing only by some degree its intensity. Morbidity and incapacity in treated patients and in cured ones paradoxically appeared to be higher than in untreated persons. High parasitocidal activity of praziquantel in trematode infections has tempted (20) to use the drug as a tool in improving the level of health of population of endemic areas. For areas with a moderate and with a high rates of the infection "radical" and "selective" treatment with praziquantel was proposed (6). The study of clinical and immunological parameters in aboriginal, settler and migrant population of hyperendemic area in the Ob-Irtysh basin--Khanty-Mansi Autonomous District revealed striking differences in the groups and their different responses to praziquantel treatment. The possibility of transplacental transmission of O. felineus antigens in aborigines and in a part of settlers leading to immunological tolerance was revealed. "Retreatment" with praziquantel can lead to the loss of the latter and can challenge higher morbidity in adults and unsafety of their progeny. Monitoring system, checking the results of "retreatment" with praziquantel is proposed.