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A study published in the British scientific journal Nature and relayed by the radio station Franceinfo sounded the alarm on the important role played by the reservoirs of both large and small dams in mosquito reproduction and the transmission of malaria.
Dams at the heart of development in sub-Saharan Africa
Dam building is the cornerstone of the development strategy of sub-Saharan States, to ensure food security and energy supplies for their populations. 160 dams are currently being built and others are scheduled to meet the continent’s forever more pressing challenges of development. These dams receive numerous funds from international funding bodies such as the World Bank.
The dilemma of choosing between development and public health
The study, carried out on the Volta, the Limpopo, the Zambezi and the Omo-Turkana, showed that these dams are also the best allies of malaria, causing up to 1.7 million cases annually. The scientists showed that the general impact of the dams in the transmission of malaria has been underestimated, and they emphasize the specific role played in this transmission by small dams, which they say represent the biggest risk of malaria in the four basins studied. According to their estimates, the incidence of malaria is two to seven times higher per kilometre from the banks of reservoirs for small dams than for the large dams of the same basin.
This difference can be explained by different elements: most small dams are built for small scale irrigation and to supply water for livestock. Thus, they are located very close to dwellings. Consequently, the density of the population around small dams is higher. 14.7 million people live near a dam in the four basins studied, i.e. within a perimeter of less than 5 km around a reservoir. Of these 14.7 million people, most of them (12.3 million) live near a reservoir of a small dam.
Also, these small dams are rarely dedicated to electricity production. Thus, they are lower, resulting in inadequate drainage that favours the persistence of surface water and the formation of reservoir lakes that make ideal habitats for mosquitoes.
The actions to be implemented
The authors suggest stronger efforts to control malaria close to both the reservoirs of the large and small dams. They also advise implementing dam operations as a means of environmental control of the disease, by avoiding large areas of stagnant water where mosquitoes can proliferate.
To know more about mosquitoes and the diseases this insect transports nearly everywhere in the world, IFGR recommends reading the book that Erik Orsenna, Chairman of IFGR, has written about them: Géopolitique du Moustique, Petit Précis de Mondialisation IV (Geopolitics of the Mosquito, A Brief Manual of Globalisation), Fayard, 2017.
“Mosquitoes can be traced back to the dawn of time (250 million years ago), but their lives are short (average lifespan: 30 days). Plentiful (3,564 species), voluntarily dangerous (more than 700,000 human beings die every year), they can be found on the five continents (as well as Greenland). When they hum in our ears, they are telling us a story: their opinion about globalisation. A story of vanishing borders, permanent mutations, fights for survival and global health, but also that of the (vertiginous) human powers provided by genetic engineering. Will we become apprentice sorcerers? However, let’s not be fooled, it’s above all a story of a couple with three components: the mosquito, the parasite and its prey (us, vertebrates). Let’s set off for a new journey so we can try to better understand our Earth. French Guiana, Cambodia, Pekin, Senegal and Brazil, without forgetting the mythical forest Zika (Uganda): surprises and fevers!”