Climate Change Fueling Malaria in Kenya, Experts Say

Eliza Barclay in Tumutumu, Kenya
for National Geographic News
January 9, 2008

Esther Njoki lay on a slender cot in the women's ward of Tumutumu Hospital, lucid for the first time in days after being ambushed by fever and delirium. The emaciated 80-year-old had survived a bout of malaria, but her doctor said it nearly killed her.

Malaria has long been endemic to Kenya's humid coast and swampy lowland regions, but it has only rarely reached Njoki's village on the slopes of Mount Kenya (see Kenya map).

In recent decades, however, scientists have noted an increase in epidemics in the region, as well as in sporadic cases like Njoki's.

Many medical and environmental experts attribute the spike in malaria to climate change, in the form of warmer temperatures and variations in rainfall patterns. (See a map of global warming's effects.)

"We are now finding malaria in places that we did not expect to find it, particularly the highland regions that used to be too cool for malaria," said Dorothy Memusi, deputy director of the Malaria Division in Kenya's Ministry of Health.

Parasites, Mosquitoes Affected by Climate

Malaria is an infectious disease caused by parasites in the blood system. Symptoms include fever, severe joint pain, and in extreme cases, anemia—a deficiency in red blood cells—because the parasites use red blood cells to reproduce.

Changes in temperature can affect the development and survival of malaria parasites and the mosquitoes that carry them, according to a joint 2004 study by the State University of New York, Buffalo, and the Kenya Medical Research Institute.

Rainfall also influences the availability of mosquito habitats and the size of mosquito populations, the research found.

Shem Wandiga is a professor of chemistry at University of Nairobi who has studied the relationship between climate and malaria.

He said malaria epidemics first appeared in Kenya's highlands in the 1920s, but during the last 20 years, the frequency of outbreaks in the region has been more pronounced.

"The best climate conditions for malaria are a long rainy season that is warm and wet, followed by a dry season that is not too hot, followed by a hot and wet short rainy season," Wandiga said.

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