Prevalence of human cystic echinococcosis in the towns of Ñorquinco and Ramos Mexia in Rio Negro Province, Argentina, and direct risk factors for infection

Abstract

Background Cystic echinococcosis (CE) is a parasitic zoonosis caused by infection with the larval stage of Echinococcus granulosus (s.l.). This study investigated the prevalence and potential risk factors associated with human CE in the towns and rural areas of Ñorquinco and Ramos Mexia, Rio Negro province, Argentina. Methods To detect abdominal CE cysts, we screened 892 volunteers by ultrasound and investigated potential risk factors for CE using a standardized questionnaire. Prevalence ratio (PR) with 95% confidence intervals (CI) was used to measure the association between CE and the factors investigated, applying bivariate and multivariate analyses. Results Abdominal CE was detected in 42/892 screened volunteers (4.7%, 95% CI 3.2–6.1), only two of whom were under 15 years of age. Thirteen (30.9%) CE cases had 25 cysts in active stages (CE1, CE2, CE3a, according to the WHO Informal Working Group on Echinococcosis [WHO-IWGE] classification). The most relevant risk factors identified in the bivariate analysis included: living in rural areas (P = 0.003), age > 40 years (P = 0.000), always drinking water from natural sources (P = 0.007), residing in rural areas during the first 5 years of life (P = 0.000) and having lived more than 20 years at the current address (P = 0.013). In the multivariate final model, the statistically significant risk factors were: frequently touching dogs (P = 0.012), residing in rural areas during the first 5 years of life (P = 0.004), smoking (P = 0.000), age > 60 years (P = 0.002) and living in rural areas (P = 0.017). Conclusions Our results point toward infection with CE being acquired since childhood and with constant exposure throughout life, especially in rural areas with a general environmental contamination. Graphic Abstract

The Diagnosis, Treatment, Surveillance and Control of Cystic Echinococcosis in the Province of Rio Negro: The “One-Health” Model

“…In this region, which the highest number of cases in the province, sheep and goat farming are the main production activities, thus providing ideal epidemiological conditions due to the lasting habits of slaughtering adult sheep, followed by delivery of viscera to dogs; other important factors include an excessive number of dogs, a lack of drinking water, and weather conditions, all of which favor the survival of Echinococcus granulosus eggs in the environment [6,[10][11][12]. In this region, which the highest number of cases in the province, sheep and goat farming are the main production activities, thus providing ideal epidemiological conditions due to the lasting habits of slaughtering adult sheep, followed by delivery of viscera to dogs; other important factors include an excessive number of dogs, a lack of drinking water, and weather conditions, all of which favor the survival of Echinococcus granulosus eggs in the environment.…”

“…In this region, which the highest number of cases in the province, sheep and goat farming are the main production activities, thus providing ideal epidemiological conditions due to the lasting habits of slaughtering adult sheep, followed by delivery of viscera to dogs; other important factors include an excessive number of dogs, a lack of drinking water, and weather conditions, all of which favor the survival of Echinococcus granulosus eggs in the environment. [6,[10][11][12]…”

“…In all cases, the main subjects are schoolchildren (aged 6 to 14 years old), although spot screenings are also carried out in all age groups [6,17]. Surveys of schoolchildren in rural areas are conducted on an annual basis, thus ensuring early diagnosis and a system of surveillance of CE disease among the population.…”

“…Primary endemic foci occur in marginal rural areas, which are often (although not exclusively) linked to both low social and economic conditions and sheep and goat production; thus, producers and their families (native communities very often included) who raise sheep and goats as their main means of subsistence, are more commonly affected by CE. Secondary endemic foci occur in the periphery of cities (suburban neighborhoods) close to endemic areas, in relation to migratory flows from the countryside to the city, with the subsequent transfer of habits and customs that lead to the appearance of cases in marginal, peri-urban populations [4][5][6].…”

“…In 1980, the Ministry of Health of the Province of Rio Negro launched a Control Program against CE, with activities related to its diagnosis, treatment, surveillance and control [6,[10][11][12].…”