A new peer-reviewed study released last week has linked large dams in Sub-Saharan Africa to over a million malaria cases annually.
The study, “Malaria impact of large dams in sub-Saharan Africa: maps, estimates and predictions,” whose finding were announced in South Africa on September 11th and published in this month’s Malaria Journal, was undertaken as part of the Consultative Group on International Agricultural Research (CGIAR) Research Program on Water, Land and Ecosystems.
The study looked at 1,268 dams in sub-Saharan Africa. It correlated the location of large dams with incidence of malaria, and suggested that construction of an expected 78 major new dams in sub-Saharan Africa over the next few years will lead to an additional 56,000 malaria cases annually.
Biologist Solomon Kibret, the paper’s lead author, said dams are at the center of much development planning in Africa, but while they bring many benefits, they will undermine the sustainability of the continent’s drive for development.
However, Matthew McCartney, a principal researcher in the study and a specialist in water resources, wetland and hydro-ecological studies, added that there are no viable alternatives to dams as source of water in Sub-Saharan Africa, despite the malaria burden.
McCartney, who is also the International Water Management Institute’s (IWMI) head of office in Vientiane, Laos, said large dams are essential for irrigation, domestic, and industrial water supply and hydropower.
“Although in some instances there may be other options such as greater utilization of groundwater or alternative energy sources to hydropower that could be given consideration, large dams will continue to play a key role in socio-economic development for the foreseeable future,” he said.
He said the study did not quantify the economic losses to communities living close to the dams, but estimated that, in total, 174 million cases of malaria cause economic losses of over $12 billion USD across Africa every year.
The study recommended various ways of managing malaria. In the case of a country like Kenya, which has a high malaria burden even in communities not affected by dams, McCartney said there is no “silver bullet” to fighting the disease.
“Malaria is a complex disease that is not easy to combat. Its control requires a multi-pronged approach that focuses both on prevention and treatment," he said. "A combination of vector control measures and prompt case treatment has been proven to manage the risk of malaria in some cases. However, these measures are costly and not always effective."
He suggested several unconventional approaches to malaria prevention. One of these is making sure dams are built in areas where there is either no malaria, or stable transmission.
Another method of vector control is reservoir management, which modifies dam operating schedules so that at critical times the shores of the reservoir, where mosquitoes breed, is dried out and the mosquito larvae die.
“This was done in the past for reservoirs in the Tennessee River Valley in the United States, and our previous work showed that it might be effective in some instances in Africa,” McCartney said. “However, for a country like Kenya, research would need to be conducted to test its efficacy.”
A third unconventional approach involves introducing larvivorous fish to reduce the abundance of mosquito larvae.
“None of these unconventional approaches will work everywhere, and none would work in isolation from conventional measures,” McCartney noted. “They would all obviously have costs associated with them, so there are indeed trade-offs.”
He said it is crucial that dam operators and public health authorities in Kenya acknowledge the likelihood of increased malaria in the vicinity of large dam reservoirs, such as the planned high falls dam on the Tana River, and coordinate closely to implement mitigation measures.
Improved coordination between malaria research and relevant policymaking is also needed. “If the disconnect between research and policymaking could be overcome it would go a long way to improving outcomes,” he said.