Lautze Dams Malaria in Ethiopia

By Julia C. Keller

Worldwide malaria kills more than a million people a year. Ninety percent of these deaths occur in Africa, mostly among young children. Jonathan Lautze is researching how to curb the transmission of malaria through water resource engineering and management—research he pursued while completing Tufts School of Engineering's first doctoral degree in conjunction with the interdisciplinary Water: Systems, Science, and Society certificate program. By controlling a dam's reservoir water levels, the development of malaria-carrying mosquito larvae can be disrupted.

Lautze says his research is part of an integrated strategy needed to address the spread of malaria hotspots, the control of malaria transmission, and the subsequent malaria treatment if the first prongs of attack fail. “Malaria is increasing in Africa and you need a bundle of measures to deal with it," says Lautze. "If you were trying to decide the answer to 'How do you best to control malaria?' in a multiple choice question, you’d want another letter to say 'All of the above.'”

“Jonathan’s work exemplifies the need for an interdisciplinary partnership between engineers and public health experts and other stakeholders,” says Paul Kirshen, director of the WSSS program. “A health crisis like malaria must be informed by engineering research, and engineers must understand the far-reaching, public health impact of their constructions.”
 
Malaria is classified as a water-borne disease even though people don't contract it through drinking water and ingesting parasites like giardia and cholera. The single-celled malaria parasite is transmitted through the saliva of a vector—the Anopheles mosquito—whose lifecycle is dependent on the presence of water. “Mosquitoes are highly sophisticated, and different species of mosquitoes have different preferred breeding habitats," Lautze says, including water pools created from rainfall, water storage tanks, or the shorelines of dam reservoirs. Adult female mosquitoes lay up to 200 eggs in water where the larvae take between one and two weeks to develop. After reaching adulthood, the winged blood-suckers take flight looking for a source of nourishment in the form of blood.

If the mosquitoes don't encounter bed nets, chemical sprays such as DDT, or the slap of a human hand, they may fly on to feed on people infected with malaria. Inside the human host, the malaria parasite evades the immune system, infecting the liver and red blood cells, and develops into a form mosquitoes acquire when having a blood meal. Once inside the mosquito, the parasite takes as little as 10 days to mature until it can infect a new human host who continues the cycle.
 
Lautze first became acquainted with malaria between 1999 and 2001 when he worked as a math teacher in the Peace Corps in Benin, a country in West Africa sandwiched between Nigeria and Togo. In Benin, Lautze saw first-hand how malaria transmission tracked closely with water. In that area, "water" means precipitation. Rain leaves puddles that create breeding habitats perfect for the local type of Anopheles mosquitoes. "On the west African coast, you have more year-round rainfall and therefore puddles year round," Lautze says.

This leads to what researchers call "stable transmission" rates of malaria. In this case, "stable" means higher, overall rates of malaria transmission because the mosquitoes' breeding habitats are habitually present. "In other areas, where you have a peak of concentrated rainfall or temperature increase, you have less intense or 'unstable' transmission," he says. In the East African highlands of Ethiopia and Kenya, malaria transmission is generally “unstable.” The construction of dams for water collection and subsequent irrigation has created year-round breeding sites for mosquitoes, kicking malaria transmission into high gear.
 
The effect of manmade dam construction on disease transmission was a lesson learned in the American south in the first half of the century following dam construction propelled forward by Franklin Roosevelt's New Deal. The creation of the dams brought much needed employment and hydropower, but had the unintended consequence of increased malaria. While pursuing his doctorate in the Tufts WSSS graduate program, Lautze worked with Harvard School of Public Health professor Andrew Spielman.

In the 1950s, Spielman consulted with the Tennessee Valley Authority on the management of water reservoirs created by the New Deal dams. To control malaria, the TVA introduced concepts of raising and lowering the levels in the reservoir in an effort to stem the breeding of mosquitoes. Though the TVA's reservoir management policies helped reduce malaria transmission, the control of water-levels were implemented without a rigorous assessment of their malaria-reducing impacts, Lautze says. More rigorous, quantitative research into the interdependence of water-level changes and mosquito larvae development drove Lautze back to Africa, this time to the east of the continent in Ethiopia.
 
Lautze headed to the Koka Dam, located on the Awash River in the Ethiopian Rift Valley, 60 miles southeast of the capital, Addis Ababa. Constructed in 1961, Koka Dam is operated to satisfy four major objectives: hydropower, irrigation, flood control and drought prevention. "The Koka Dam was the first large dam constructed in Ethiopia," says Lautze. "The original intention was to provide hydropower to the capital," he says, adding, "During the rainy season, when they know a lot of water’s coming in, they’ll release a lot of water from the reservoir. Also, there’s a minimum to keep in the reservoir between years to mitigate a drought," Lautze says. Koka is also used for irrigation of Wonji sugar plantation, located nearby.

Ethiopia is experiencing a resurgence of dam construction for hydropower through investors in China and at the World Bank where Lautze now works as a consultant. "Because Ethiopia is developing a lot of hydropower sites now, the [electricity producing] impact of a particular dam like Koka is diminishing," he says, “which increases the operational flexibility to accommodate additional objective like malaria control.”
 

To study malaria transmission in village clusters, called kebeles, Lautze worked with contacts at international water resource management and people in public health. Lautze chose Koka because of the strong health data collected in the area. He sifted through eight years of malaria case data from malaria control centers surrounding the Koka reservoir. In the data collected from 1994-2002, Lautze found a kebele's geographic distance from the Koka reservoir shoreline correlated with malaria transmission, with rates about 2.3 times greater for villages located less than three kilometers (about 1.8 miles) from the reservoir compared to those located six to nine kilometers farther away. Lautze also correlated reservoir water levels with fieldwork along the shoreline to determine prevalence of mosquito larvae. Lautze says, the reservoir shoreline continues to be the most important breeding habitat for any kebele surrounding the reservoir. His data points to the conclusion that lowering reservoir levels faster than half a meter over a month results in fewer mature mosquito larvae and therefore reduced malaria transmission.
 
Though Lautze's research is robust and straightforward, he says carrying out his recommendations may not happen immediately. "The point between publishing this data and implementing this is several years," he says. "When you build a dam and have a reservoir, you know there’s going to be some tradeoffs because you’re going to have competing objectives,”—and not only among the water resource management group. Lautze says the disconnect between the water and public health sector often creates barriers to devising the best approach to control malaria. But given global warming, all competing interests are running out of time. “In warmer temperatures the larvae will develop and transform into adults more rapidly than in colder temperatures,” says Lautze. With increased temperatures in Ethiopia and elsewhere, transmission rates will only increase and malaria control will become increasingly complex.

In the meantime, Lautze continues his work with water management in Africa through the World Bank. He also has a graduate student carrying on the water resource management research he began through WSSS. "Water resource people will continue to construct dams," Lautze says. "Health affects may still be an unintended consequence, but this is a good lever that can be pulled to reduce disease transmission."