Predicting the movement of malaria in response to changing climate

Working with health services in East Africa’s uplands

As climate change is affecting disease patterns, malaria for example is increasing in upland areas where it was previously rare. Climate science can help health services to be better prepared for outbreaks, and to plan for prevention in future.

Malaria is increasing where temperatures are rising

Recent years have seen outbreaks of malaria in highland areas of East Africa, where there is little experience of the disease. The relatively cool and breezy highlands of Kenya, Tanzania and Uganda have long been free of malaria, being too cold for the mosquitoes. Temperatures in the East African highlands have risen by half a degree Celsius in the last 50 years, however, mostly since the late 1970s. Even this small change may have doubled the number of malaria-carrying mosquitoes.

The 1998 epidemic of malaria in East Africa was associated with heavy rains and average temperatures in Kenya’s highlands up to four degrees higher than usual. The regional incidence of malaria increased 300 per cent over the baseline average for 1995–2002. With climate change, and other factors such as deforestation, the warmer and wetter conditions unusual in this region in the late 1990s may become the norm.

Collaboration between climate scientists and health authorities

Malaria can be especially severe in areas of low resistance, especially for mothers and children. Highland health systems were unprepared for the first malaria outbreaks. There was untold suffering and many deaths among patients who had to share hospital beds or spend days on hospital floors without proper medical care.

Climate science is a stretch for a medical research institute. But Dr Andrew Githeko and his colleagues at the Kenya Medical Research Institute (KEMRI) noticed the coincidence of malaria outbreaks in Kenya’s highlands with particular weather conditions. Medical records in Ethiopia also show a high degree of correlation between rainfall and temperature increases and malarial incidence.

Researchers led by the Kenya Medical Research Institute are now working to combine climate observation with medical research to predict highland malaria outbreaks in Kenya, Tanzania and Uganda. “These efforts will help health service providers identify early warnings of a looming epidemic, to better protect people in affected communities,” explains James Sang, of the Kenyan government’s Malaria Control Unit.

Using climate modelling to predict the movement of malaria

Warm conditions allow both the anopheles mosquito and the malarial parasite to develop more quickly, while wet conditions increase mosquito life expectancy and provide breeding habitats. “It became apparent weather data could be used to reliably predict malaria epidemics,” says Kenyan meteorologist, William Ndegwa.

The research team combines expertise from ministries of health, climate-research institutes and NGOs from Kenya, Tanzania and Uganda. After developing a model of malaria prediction, based on the detection of risk conditions, the team is able to detect epidemics some months before they occur. “The challenge now,” says project leader, Andrew Githeko, “is to develop and deploy an instrument that health system managers can use to reliably predict the onset of a malaria epidemic in areas not traditionally prone to the disease, and to manage it better.”

Mike Okia of Uganda’s Ministry of Health adds, “We aim to improve the model’s predictive capacity by taking into consideration the local terrain and the immune profile of the affected population.” The project, supported by CCAA, is also training district healthcare providers across the three countries to use the prediction model to anticipate and prepare for malaria outbreaks.

Planning for future prevention and treatment

Improved malaria prediction will be an essential part of Africa’s adaptation to climate change. While highland communities and their health providers struggle to adjust to the new prevalence of malaria, climate change is likely to bring more of it, and more often. This project aims to give local health systems better information for planning prevention and treatment.

To avoid malaria outbreaks in highland areas, where it kills more people than in lowland areas, East African governments have been depending on indoor spraying of long-lasting pesticides when long rains are anticipated. But with the new model now in place, spraying can be done only when the model suggests an outbreak is imminent. Spraying at the right time also reduces the chances of mosquitoes building resistance against the insecticides.

Each year, malaria infects over 500 million people worldwide – most of these in Africa, where malaria is the cause of one in five childhood deaths. Given the prevalence of this debilitating and often deadly disease, and the likelihood that climate change is altering its patterns, a tool that better predicts its occurrence may have impacts far beyond East Africa’s highlands. The United Nations has selected this predictive model as an example of practical adaptation to climate change, and strongly suggested that the model is further developed.  The research team believes that the model could also predict the course of other diseases.