Living near dams increases malaria risk, study shows

A dam in Africa

Photo courtesy of the

International Water

Management Institute

More than 1 million people in sub-Saharan Africa will contract malaria this year because they live near a large dam, according to a study published in Malaria Journal.

For the first time, researchers correlated the location of large dams in sub-Saharan Africa with the incidence of malaria.

And they found evidence to suggest that construction of an expected 78 major new dams over the next few years will lead to an additional 56,000 malaria cases annually.

The researchers said these findings have major implications for new dam projects and how health impacts should be assessed prior to construction.

“Dams are at the center of much development planning in Africa,” said study author Solomon Kibret, a graduate student at the University of New England in Armidale, New South Wales, Australia.

“While dams clearly bring many benefits—contributing to economic growth, poverty alleviation, and food security—adverse malaria impacts need to be addressed or they will undermine the sustainability of Africa’s drive for development.”

As part of the CGIAR Research Program on Water, Land, and Ecosystems, Kibret and colleagues looked at 1268 dams in sub-Saharan Africa. Of these, just under two-thirds (n=723) are in malarious areas.

The researchers compared detailed maps of malaria incidence with the dam sites. The number of annual malaria cases associated with the dams was estimated by comparing the number of cases for communities less than 5 kilometers from the dam reservoir with the number of cases for communities further away.

The team found that 15 million people live within 5 kilometers of dam reservoirs and are therefore at risk of contracting malaria. And at least 1.1 million malaria cases annually are linked to the presence of the dams.

“Our study showed that the population at risk of malaria around dams is at least 4 times greater than previously estimated,” Kibret said, noting that the authors were conservative in all their analyses.

The risk is particularly high in areas of sub-Saharan Africa with “unstable” malaria transmission, where malaria is seasonal. The study indicated that the impact of dams on malaria in unstable areas could either lead to intensified malaria transmission or change the nature of transmission from seasonal to perennial.

Explaining the risk

Previous research revealed increases in malaria incidence near major sub-Saharan dams such as the Akosombo Dam in Ghana, the Koka Dam in Ethiopia, and the Kamburu Dam in Kenya. But until now, no attempt has been made to assess the cumulative effect of large dam-building on malaria.

Malaria is transmitted by the Anopheles mosquito, which needs slow-moving or stagnant water in which to breed. Dam reservoirs, particularly shallow puddles that often form along shorelines, provide a perfect environment for the insects to multiply. Thus, dam construction can intensify transmission and shift patterns of malaria infection.

Many African countries are planning new dams to help drive economic growth and increase water security. Improved water storage for growing populations, irrigation, and hydropower generation are needed for a fast-developing continent, but the researchers warn that building new dams has potential costs as well as benefits.

“Dams are an important option for governments anxious to develop,” said study author Matthew McCartney, PhD, of the International Water Management Institute in Vientiane, Laos.

“But it is unethical that people living close to them pay the price of that development through increased suffering and, possibly in extreme cases, loss of life due to disease.”

Lowering the risk

The researchers noted that, despite growing evidence of the impact of dams on malaria, there is scant evidence of their negative impacts being fully offset.

The team therefore made recommendations for managing the increased malaria risk. They said dam reservoirs could be more effectively designed and managed to reduce mosquito breeding. For instance, one option is to adopt operating schedules that, at critical times, dry out shoreline areas where mosquitoes tend to breed.

The researchers said dam developers should also consider increasing investment in integrated malaria intervention programs that include measures such as bed net distribution. Other environmental controls, such as introducing fish that eat mosquito larva in dam reservoirs, could also help reduce malaria cases in some instances.

“The bottom line is that adverse malaria impacts of dams routinely receive recognition in Environmental Impact Assessments, and areas around dams are frequently earmarked for intensive control efforts,” said study author Jonathan Lautze, PhD, of the International Water Management Institute in Pretoria, South Africa.

“The findings of our work hammer home the reality that this recognition and effort—well-intentioned though it may be—is simply not sufficient. Given the need for water resources development in Africa, malaria control around dams requires interdisciplinary cooperation, particularly between water and health communities. Malaria must be addressed while planning, designing, and operating African dams.”

A dam in Africa

Photo courtesy of the

International Water

Management Institute

More than 1 million people in sub-Saharan Africa will contract malaria this year because they live near a large dam, according to a study published in Malaria Journal.

For the first time, researchers correlated the location of large dams in sub-Saharan Africa with the incidence of malaria.

And they found evidence to suggest that construction of an expected 78 major new dams over the next few years will lead to an additional 56,000 malaria cases annually.

The researchers said these findings have major implications for new dam projects and how health impacts should be assessed prior to construction.

“Dams are at the center of much development planning in Africa,” said study author Solomon Kibret, a graduate student at the University of New England in Armidale, New South Wales, Australia.

“While dams clearly bring many benefits—contributing to economic growth, poverty alleviation, and food security—adverse malaria impacts need to be addressed or they will undermine the sustainability of Africa’s drive for development.”

As part of the CGIAR Research Program on Water, Land, and Ecosystems, Kibret and colleagues looked at 1268 dams in sub-Saharan Africa. Of these, just under two-thirds (n=723) are in malarious areas.

The researchers compared detailed maps of malaria incidence with the dam sites. The number of annual malaria cases associated with the dams was estimated by comparing the number of cases for communities less than 5 kilometers from the dam reservoir with the number of cases for communities further away.

The team found that 15 million people live within 5 kilometers of dam reservoirs and are therefore at risk of contracting malaria. And at least 1.1 million malaria cases annually are linked to the presence of the dams.

“Our study showed that the population at risk of malaria around dams is at least 4 times greater than previously estimated,” Kibret said, noting that the authors were conservative in all their analyses.

The risk is particularly high in areas of sub-Saharan Africa with “unstable” malaria transmission, where malaria is seasonal. The study indicated that the impact of dams on malaria in unstable areas could either lead to intensified malaria transmission or change the nature of transmission from seasonal to perennial.

Explaining the risk

Previous research revealed increases in malaria incidence near major sub-Saharan dams such as the Akosombo Dam in Ghana, the Koka Dam in Ethiopia, and the Kamburu Dam in Kenya. But until now, no attempt has been made to assess the cumulative effect of large dam-building on malaria.

Malaria is transmitted by the Anopheles mosquito, which needs slow-moving or stagnant water in which to breed. Dam reservoirs, particularly shallow puddles that often form along shorelines, provide a perfect environment for the insects to multiply. Thus, dam construction can intensify transmission and shift patterns of malaria infection.

Many African countries are planning new dams to help drive economic growth and increase water security. Improved water storage for growing populations, irrigation, and hydropower generation are needed for a fast-developing continent, but the researchers warn that building new dams has potential costs as well as benefits.

“Dams are an important option for governments anxious to develop,” said study author Matthew McCartney, PhD, of the International Water Management Institute in Vientiane, Laos.

“But it is unethical that people living close to them pay the price of that development through increased suffering and, possibly in extreme cases, loss of life due to disease.”

Lowering the risk

The researchers noted that, despite growing evidence of the impact of dams on malaria, there is scant evidence of their negative impacts being fully offset.

The team therefore made recommendations for managing the increased malaria risk. They said dam reservoirs could be more effectively designed and managed to reduce mosquito breeding. For instance, one option is to adopt operating schedules that, at critical times, dry out shoreline areas where mosquitoes tend to breed.

The researchers said dam developers should also consider increasing investment in integrated malaria intervention programs that include measures such as bed net distribution. Other environmental controls, such as introducing fish that eat mosquito larva in dam reservoirs, could also help reduce malaria cases in some instances.

“The bottom line is that adverse malaria impacts of dams routinely receive recognition in Environmental Impact Assessments, and areas around dams are frequently earmarked for intensive control efforts,” said study author Jonathan Lautze, PhD, of the International Water Management Institute in Pretoria, South Africa.

“The findings of our work hammer home the reality that this recognition and effort—well-intentioned though it may be—is simply not sufficient. Given the need for water resources development in Africa, malaria control around dams requires interdisciplinary cooperation, particularly between water and health communities. Malaria must be addressed while planning, designing, and operating African dams.”

A dam in Africa

Photo courtesy of the

International Water

Management Institute

More than 1 million people in sub-Saharan Africa will contract malaria this year because they live near a large dam, according to a study published in Malaria Journal.

For the first time, researchers correlated the location of large dams in sub-Saharan Africa with the incidence of malaria.

And they found evidence to suggest that construction of an expected 78 major new dams over the next few years will lead to an additional 56,000 malaria cases annually.

The researchers said these findings have major implications for new dam projects and how health impacts should be assessed prior to construction.

“Dams are at the center of much development planning in Africa,” said study author Solomon Kibret, a graduate student at the University of New England in Armidale, New South Wales, Australia.

“While dams clearly bring many benefits—contributing to economic growth, poverty alleviation, and food security—adverse malaria impacts need to be addressed or they will undermine the sustainability of Africa’s drive for development.”

As part of the CGIAR Research Program on Water, Land, and Ecosystems, Kibret and colleagues looked at 1268 dams in sub-Saharan Africa. Of these, just under two-thirds (n=723) are in malarious areas.

The researchers compared detailed maps of malaria incidence with the dam sites. The number of annual malaria cases associated with the dams was estimated by comparing the number of cases for communities less than 5 kilometers from the dam reservoir with the number of cases for communities further away.

The team found that 15 million people live within 5 kilometers of dam reservoirs and are therefore at risk of contracting malaria. And at least 1.1 million malaria cases annually are linked to the presence of the dams.

“Our study showed that the population at risk of malaria around dams is at least 4 times greater than previously estimated,” Kibret said, noting that the authors were conservative in all their analyses.

The risk is particularly high in areas of sub-Saharan Africa with “unstable” malaria transmission, where malaria is seasonal. The study indicated that the impact of dams on malaria in unstable areas could either lead to intensified malaria transmission or change the nature of transmission from seasonal to perennial.

Explaining the risk

Previous research revealed increases in malaria incidence near major sub-Saharan dams such as the Akosombo Dam in Ghana, the Koka Dam in Ethiopia, and the Kamburu Dam in Kenya. But until now, no attempt has been made to assess the cumulative effect of large dam-building on malaria.

Malaria is transmitted by the Anopheles mosquito, which needs slow-moving or stagnant water in which to breed. Dam reservoirs, particularly shallow puddles that often form along shorelines, provide a perfect environment for the insects to multiply. Thus, dam construction can intensify transmission and shift patterns of malaria infection.

Many African countries are planning new dams to help drive economic growth and increase water security. Improved water storage for growing populations, irrigation, and hydropower generation are needed for a fast-developing continent, but the researchers warn that building new dams has potential costs as well as benefits.

“Dams are an important option for governments anxious to develop,” said study author Matthew McCartney, PhD, of the International Water Management Institute in Vientiane, Laos.

“But it is unethical that people living close to them pay the price of that development through increased suffering and, possibly in extreme cases, loss of life due to disease.”

Lowering the risk

The researchers noted that, despite growing evidence of the impact of dams on malaria, there is scant evidence of their negative impacts being fully offset.

The team therefore made recommendations for managing the increased malaria risk. They said dam reservoirs could be more effectively designed and managed to reduce mosquito breeding. For instance, one option is to adopt operating schedules that, at critical times, dry out shoreline areas where mosquitoes tend to breed.

The researchers said dam developers should also consider increasing investment in integrated malaria intervention programs that include measures such as bed net distribution. Other environmental controls, such as introducing fish that eat mosquito larva in dam reservoirs, could also help reduce malaria cases in some instances.

“The bottom line is that adverse malaria impacts of dams routinely receive recognition in Environmental Impact Assessments, and areas around dams are frequently earmarked for intensive control efforts,” said study author Jonathan Lautze, PhD, of the International Water Management Institute in Pretoria, South Africa.

“The findings of our work hammer home the reality that this recognition and effort—well-intentioned though it may be—is simply not sufficient. Given the need for water resources development in Africa, malaria control around dams requires interdisciplinary cooperation, particularly between water and health communities. Malaria must be addressed while planning, designing, and operating African dams.”