A combined field study of Buruli ulcer disease in southeast Benin proposing preventive strategies based on epidemiological, geographic, behavioural and environmental analyses

Abstract

Buruli ulcer is a neglected tropical disease caused by M. ulcerans, an environmental mycobacterium. This cutaneous infectious disease affects populations with poor access to sanitation, safe water and healthcare living in rural areas of West and Central Africa. Stagnant open bodies of surface water and slow-running streams are the only risk factor identified in Africa, and there is no human-to-human transmission. Appropriate and effective prevention strategies are required for populations living in endemic areas. Based on a multidisciplinary approach in an area in which Buruli ulcer is endemic in South Benin, we investigated the link between all human-environment interactions relating to unprotected water and behaviors associated with Buruli ulcer risk likely to affect incidence rates. We characterised the sources of water as well as water bodies and streams used by communities, by conducting a prospective case-control study directly coupled with geographic field observations, spatial analysis, and the detection of M. ulcerans in the environment. A full list of the free surface waters used for domestic activities was generated for a set of 34 villages, and several types of human behaviour associated with a higher risk of transmission were identified: (i) prolonged walking in water to reach cultivated fields, (ii) collecting water, (iii) and swimming. Combining the results of the different analyses identified the risk factor most strongly associated with Buruli ulcer was the frequency of contact with unprotected and natural water, particularly in regularly flooded or irrigated lowlands. We confirm that the use of clean water from drilled wells confers protection against Buruli ulcer. These specific and refined results provide a broader scope for the design of an appropriate preventive strategy including certain practices or infrastructures observed during our field investigations. This strategy could be improved by the addition of knowledge about irrigation practices and agricultural work in low-lying areas.

Perceived water-related risk factors of Buruli ulcer in two villages of south-central Côte d’Ivoire

“…At times, these are the only available water sources in the study villages. Overall, water contact patterns observed and reported by the interviewees are in line with case studies from similar settings in West Africa [ 25 , 32 ]. To compare and contrast perceived risk factors more comprehensively, it would be interesting to investigate water contact patterns longitudinally in multiple sites considering households with and without Buruli ulcer cases.…”

“…In Ghana, several studies were carried out in the Densu River Basin [44] and the Offin River [27,45]. In Benin, multiple studies were done in the Oue ´me ´and Plateau districts, including seminal investigations of the PLOS NEGLECTED TROPICAL DISEASES impacts of water sources on Buruli ulcer [25,32]. A recent study suggests that improved water infrastructure is associated with lower number of Buruli ulcer cases [32].…”

“…Nonetheless, findings indicate that M . ulcerans can persist in aquatic environments such as wetlands or side streams of rivers [ 24 ] and, indeed, aquatic reservoirs appear to play an important role in transmission [ 25 – 27 ]. In the south-eastern part of Australia, possums have been identified as animal reservoir [ 28 , 29 ].…”

“…However, for unknown reasons, reported PCR positivity from environmental studies in settings that are endemic for Buruli ulcer in Africa differ substantially. Nonetheless, findings indicate that M. ulcerans can persist in aquatic environments such as wetlands or side streams of rivers [24] and, indeed, aquatic reservoirs appear to play an important role in transmission [25][26][27]. In the south-eastern part of Australia, possums have been identified as animal reservoir [28,29].…”

Utilising community volunteers can increase the detection and referral of Buruli ulcer cases in endemic communities in Southeast, Nigeria

“…Additionally, they are prone to frequent contact with unprotected water sources, which is an associated factor with BU. A study in Benin reported that access to unprotected water bodies, with emphasis on flooded lowlands, is implicated in a rise in BU cases [ 22 ]. Another implication of this finding could be the constant use of bodies of water for agriculture.…”