Human echinococcosis in Bulgaria: a comparative epidemiological analysis.

The present article describes the importance of human echinococcosis as a public health problem in Bulgaria, outlines the control measures carried out and evaluates comparatively the situation over three periods spanning 46 years (1950-1995). During the first period (1950-62), a total of 6469 new surgically confirmed cases of hydatid disease were recorded in Bulgaria, with an annual incidence of 6.5 per 100,000 population, and the infestation rate in domestic animals and dogs was high. Echinococcosis was endemic throughout the country. The organization of a control campaign, initiated in 1960, led to a considerable improvement in the situation during the second period (1971-82). Morbidity among humans gradually decreased, with an average incidence of 2.0 per 100,000, and the proportion of infected animals also fell. The distribution of echinococcosis was characterized as sporadic or of low endemicity. During the third period (1983-95), owing to administrative irregularities and economic changes, funds for supporting the campaign were reduced and control structures were dismantled. As a result, the incidence rose to 3.3 per 100,000. Echinococcosis again became endemic, in some regions hyperendemic. The findings provide convincing evidence that cessation of control measures or reduction of campaign activity can lead to intensification in the transmission of Echinococcus granulosus and to a resurgence in echinococcosis to previous levels.