Socio-Environmental Factors Associated with the Risk of Contracting Buruli Ulcer in Tiassalé, South Côte d’Ivoire: A Case-Control Study

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Abstract
Buruli ulcer (BU) is a cutaneous infectious disease caused by Mycobacterium ulcerans. The exact mode of transmission remains elusive; yet, some studies identified environmental, socio-sanitary, and behavioral risk factors. The purpose of this study was to assess the association of such factors to contracting BU in Tiassalé, south Côte d’Ivoire. A case-control study was conducted in 2012. Cases were BU patients diagnosed according to clinical definition put forth by the World Health Organization, readily confirmed by IS2404 polymerase chain reaction (PCR) analysis prior to our study and recruited at one of the health centers of the district. Two controls were matched for each control, by age group (to the nearest 5 years), sex, and living community. Participants were interviewed after providing oral witnessed consent, assessing behavioral, environmental, and socio-sanitary factors. A total of 51 incident and prevalent cases and 102 controls were enrolled. Sex ratio (male:female) was 0.9. Median age was 25 years (range: 5–70 years). Regular contact with unprotected surface water (adjusted odds ratio (aOR) = 6.5; 95% confidence interval (CI) = 2.1–19.7) and absence of protective equipment during agricultural activities (aOR = 18.5, 95% CI = 5.2–66.7) were identified as the main factors associated with the risk of contracting BU. Etiologic fractions among exposed to both factors were 84.9% and 94.6%, respectively. Good knowledge about the risks that may result in BU (aOR = 0.3, 95% CI = 0.1–0.8) and perception about the disease causes (aOR = 0.1, 95% CI = 0.02–0.3) showed protection against BU with a respective preventive fraction of 70% and 90%. Main risk factors identified in this study were the contact with unprotected water bodies through daily activities and the absence of protective equipment during agricultural activities. An effective strategy to reduce the incidence of BU should involve compliance with protective equipment during agricultural activities and avoidance of contact with surface water and community capacity building through training and sensitization. In Côte d’Ivoire, West Africa, Buruli ulcer (BU) is the second leading cause of mycobacterial infection after tuberculosis. Moreover, Côte d’Ivoire is one of the most affected countries worldwide by BU. Studies suggest that the reservoir of this mycobacterial infection is environmental, but the exact mode of disease transmission is still not known. The main strategy for the control of BU is early detection of cases and to treat them with antibiotics. In order to improve our understanding of the risk for contracting BU, which would allow primary prevention of the disease, a case-control study was conducted in 2012 in the district of Tiassalé, located in the southern part of Côte d’Ivoire, where the rain forest meets the savannah. We found that regular contact with unprotected surface water was an important factor associated with the risk of contracting BU. Such water contacts occur during agricultural activities, as well as washing, bathing, and swimming practices. An effective strategy to prevent BU in the district of Tiassalé–and perhaps in other endemic areas–will have to focus on improved access to clean water at the household, and sensitization and education for better practices in subsistence agriculture.

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