Simulium damnosum s.l., the most important vector of onchocerciasis in Africa, is a complex of sibling species described on the basis of differences in their larval polytene chromosomes. These (cyto) species differ in their geographical distributions, ecologies and epidemiological roles. In Togo and Benin, distributional changes have been recorded as a consequence of vector control and environmental changes (e.g. creation of dams, deforestation), with potential epidemiological consequences. We review the distribution of cytospecies in Togo and Benin and report changes observed from 1975 to 2018. The elimination of the Djodji form of S. sanctipauli in south-western Togo in 1988 seems to have had no long-term effects on the distribution of the other cytospecies, despite an initial surge by S. yahense. Although we report a general tendency for long-term stability in most cytospecies’ distributions, we also assess how the cytospecies’ geographical distributions have fluctuated and how they vary with the seasons. In addition to seasonal expansions of geographical ranges by all species except S. yahense, there are seasonal variations in the relative abundances of cytospecies within a year. In the lower Mono river, the Beffa form of S. soubrense predominates in the dry season but is replaced as the dominant taxon in the rainy season by S. damnosum s.str. Deforestation was previously implicated in an increase of savanna cytospecies in southern Togo (1975-1997), but our data had little power to support (or refute) suggestions of a continuing increase, partly because of a lack of recent sampling. In contrast, the construction of dams and other environmental changes including climate change seem to be leading to decreases in the populations of S. damnosum s.l. in Togo and Benin. If so, combined with the disappearance of the Djodji form of S. sanctipauli, a potent vector, plus historic vector control actions and community directed treatments with ivermectin, onchocerciasis transmission in Togo and Benin is much reduced compared with the situation in 1975.
Recurrent floods have become a major problem in the transboundary Lower Mono River catchment of Togo and Benin, causing more damage and loss of life than any other disaster in the area. The level of understanding about floods and their management can be as diverse as the groups within the communities and thus can present a variety of perspectives. People tend to perceive flood risk and management differently due to their proximity to flood-prone areas and their level of vulnerability as well as their capacity to adapt. Therefore, this study explores the specific perspectives of local communities and experts on floods in the transboundary Mono catchment, which can help to inform better adaptation strategies according to the contexts of each community. We conducted series of focus groups discussions (FGDs) using the Actors, Resources, Dynamics, and Interactions (ARDI) framework to develop mental models of flood management. This approach allowed us to identify the causes and impact of flooding in the area, and to describe the actors and effects of flood events on the main natural resources as well as the dynamics and interactions that drive change and influence flood management in the study area. The results indicate that the perceptions of local communities and experts show both similarities and differences. These differences include (1) perceptions of relevant direct actors, (2) perceptions of resources at stake, and (3) actor-specific resource utilization. Considering these dissimilar views between expert and local community knowledge systems appears to be an important contributing factor to improving flood mitigation efforts in the catchment. Adapting risk communication and measures taken for flood management in accordance with the perceptions of affected communities could greatly increase success, with positive long-term effects for the involved institutions and communities regarding mutual trust-building.
Leptospirosis is a waterborne zoonosis (60,000 infections and 1 million deaths annually). Knowledge about the disease in the urban context is surprisingly rare, especially in Africa. Here, we provide the first study of leptospires in waters within an African city. A simple centrifugation-based method was developed to screen waterborne leptospires from remote or poorly areas. Major ions, trace elements, stable isotopes and pathogenic Leptospira were then seasonally investigated in 193 water samples from three neighborhoods of Cotonou (Benin) with different socio-environmental and hydrographic characteristics. Firstly, no leptospire was detected in tap waters. Secondly, although surface contamination cannot be excluded, one groundwater well was found leptospire positive. Thirdly, pathogenic Leptospira mainly contaminated surface waters of temporary and permanent ponds (9.5% and 27.3% of total prevalence, respectively). Isotopic signatures suggest that leptospires occurred in pond waters formed at the beginning of the rainy season following low to moderate rainfall events. Nevertheless, Leptospira-containing waters possess physico-chemical characteristics that are similar to the spectrum of waters sampled throughout the three sites, thus suggesting that Cotonou waters are widely compatible with Leptospira survival. The frequent contact with water exposes Cotonou inhabitants to the risk of leptospirosis which deserves more attention from public health authorities.
