Scientists Link Upsurge in Fatal Malaria To Temperature Rise

Malaria studies in East Africa’s highland areas show increasing incidents of fatal malaria in areas previously free of the killer disease. A team of scientists in Kenya around the Lake Victoria basin highlands, based in Kisumu is collaborating with climate scientists to feed into existing malaria preventive programs. Epidemic disease experts using seasonal climate forecast information can now predict malaria outbreaks with precision. This new development can now be used for advance strategic planning to help reduce malaria epidemics in Africa.

By Patrick Luganda
in Nairobi, Kenya.

Malaria research scientists working in the East African highland areas have confirmed increasing incidents of fatal malaria in areas previously free of the killer disease. The team of expert scientists from the Climate and Human Health Research Unit of the Kenya Medical Research Institute (KEMRI) attribute the new malaria incidents to temperature increases.

Dr. A. K. Githeko, who headed the research team, in an interview in Nairobi recently said malaria is a climate sensitive vector borne disease. He said that their studies reveal that climate variations and changes have major impacts on the behaviour of mosquitoes which are responsible for spreading the deadly disease.

“Studies from land use change and microclimate change in the western Kenya highlands are providing data on the possible impacts of climate variability of mosquito biology and malaria transmission,” said Githeko.

Githeko said temperature is an important controlling factor in the life of the mosquitoes. “The rate of malaria transmission in the highlands is controlled by temperature. Below a daily mean temperature of 18 degrees centigrade, little or no malaria transmission can occur. Below 16 degrees centigrade, malaria transmission stops. Below 14 degrees centigrade the mosquito larvae actually die,” explained the malaria expert.

Professor Laban Ogallo, Director of the IGAD Climate Prediction and Applications Centre (ICPAC) headquartered in Nairobi said that the work of the malaria research team was important and will be useful in correlating climate changes to disease incidents in the region.

“Climate scientists and other scientists in the public health sector can now put their heads together to make predictions of the likely trend of major diseases such as malaria, cholera and others. The challenge is for decision makers to use the information to make important socio economic planning in advance,” said Professor Ogallo.

Climate science specialists attribute the temperature increase to climate variability and land use change. They explain that events such as El Nino which are associated with climate variability can increase local temperature by 1-3 degrees centigrade.

Dr. Githeko explains that such climate variability can increase local temperature above the threshold of malaria transmission from 18 degrees centigrade to 21 degrees centigrade thus increasing the rate of malaria transmission substantially.

On the other hand, land use change studies carried out by the research team explain the mechanism for increased malaria transmission. Seemingly simple land use practices that are widely taken for granted result in substantial increases in malaria transmission and consequently death.

“Swamp reclamation was found to increase mean maximum water temperature by 2.4 degrees centigrade and the mean temperature by 0.8 degrees centigrade. This temperature change reduced the larval development time by 10 days thus increasing the numbers of mosquitoes in a given time interval for instance in a month,” said Dr. Githeko.

On the other hand, the team reports that deforestation increased the mean indoor temperature by 1.8 degrees centigrade. The increased mean indoor temperature, the experts said decreased time taken to digest blood in mosquitoes from 4.6 days to 2.9 days.

“This means that mosquitoes will now feed on people every three days instead of every 5 days. The result is increased malaria transmission,” said Githeko.

The research findings show that the development of malaria parasites in mosquitoes took 14 days at a highland site where the mean temperature was 21.5 degrees centigrade. In comparison malaria parasite development took 12 days at a lowland site with a mean temperature of 23.1 degrees centigrade. The researchers said means that increase in temperatures increased the rate of parasite development in mosquitoes.

Extreme climate events such as the El Nino event that caused torrential rains in 1997/98 in much of Eastern Africa had considerable impact on malaria occurrence in the various countries.

“In the epidemic prone highlands of East Africa anomalies in the mean monthly maximum of 2.2-4.5 degrees centigrade observed between January and March 1997 and 1.8-3.0 degrees centigrade in February–April 1998 were associated with 150–300% increase in admissions for malaria treatment,” the research team reported.

The research team findings have been welcomed by climate scientists as they see a lot of potential in developing models to predict epidemics.

“Results from our ecological and transmission biology studies show that increased temperatures accelerate the rate of malaria transmission. This data is helping in developing epidemic prediction models. These epidemic models are developed using meteorological data especially rainfall and temperature,” said Githeko.

Predicting malaria epidemics has immense implications on economic savings to households, communities and national budgets. Savings realized from using less drugs to cure malaria means more money freed to give services to the population.

“The average cost of treating a child with complicated malaria, which means hospital admission for 5-7 days, is about US$30.00. This is about 9% of the average income of a Kenyan whose per capita income is US$330.00. If an epidemic was forecasted and the children were treated early it would cost US$2.50 per child. The savings here would be US$27.50. So for a million children the savings would be US$27.5 m,” the team reported.