Epidemiological factors associated with human cystic echinococcosis: a semi-structured questionnaire from a large population-based ultrasound cross-sectional study in eastern Europe and Turkey

Abstract

Background: Cystic echinococcosis (CE) is a neglected parasitic zoonosis prioritized by the WHO for control. Several studies have investigated potential risk factors for CE through questionnaires, mostly carried out on small samples, providing contrasting results. We present the analysis of risk factor questionnaires administered to participants to a large CE prevalence study conducted in Bulgaria, Romania and Turkey.

Methods: A semi-structured questionnaire was administered to 24,687 people from rural Bulgaria, Romania and Turkey. CE cases were defined as individuals with abdominal CE cysts detected by ultrasound. Variables associated with CE at P < 0.20 in bivariate analysis were included into a multivariable logistic model, with a random effect to account for clustering at village level. Adjusted odds ratios (AOR) with 95% CI were used to describe the strength of associations. Data were weighted to reflect the relative distribution of the rural population in the study area by country, age group and sex.

Results: Valid records from 22,027 people were analyzed. According to the main occupation in the past 20 years, "housewife" (AOR: 3.11; 95% CI: 1.51-6.41) and "retired" (AOR: 2.88; 95% CI: 1.09-7.65) showed significantly higher odds of being infected compared to non-agricultural workers. "Having relatives with CE" (AOR: 4.18; 95% CI: 1.77-9.88) was also associated with higher odds of infection. Interestingly, dog-related and food/water-related factors were not associated with infection.

Conclusions: Our results point toward infection being acquired in a "domestic" rural environment and support the view that CE should be considered more a "soil-transmitted" than a "food-borne" infection. This result helps delineating the dynamics of infection transmission and has practical implications in the design of specific studies to shed light on actual sources of infection and inform control campaigns.

Keywords: Bulgaria; Cystic echinococcosis; Eastern Europe; Epidemiology of human infection; Potential risk factors; Romania; Semi-structured questionnaires; Turkey.

Fig. 1

Epidemiological factors associated with increased odds of human cystic echinococcosis (CE). Schematic representation of the E. granulosus life-cycle, pathways of transmission to humans (in blue), and potential risk factors associated with increased odds of human infection identified in our study (bullet points)