In contrast, most studies concluding that climate change is indeed playing a role in highland malaria tend to be statistically strong, Chaves and Koenraadt found. But just because climate is one factor influencing malaria's spread does not mean it is the only one. What is needed, the researchers say, is a research approach that combines climate with other possible factors.
"Even if trends in temperature are very small, organisms can amplify such small changes and that could cause an increase parasite transmission," Chaves said. "More biological data will improve our overall understanding of malaria and will allow scientists to propose more general and accurate models on the impacts of climate change on malaria transmission."
The authors cite numerous factors that could interact with climate to influence malaria spread. They point to research showing that people migrating from lowlands may be introducing the malaria parasite into highland regions. Changes in farming practices may also play a role. Irrigation associated with more intensive farming may be creating more places for mosquitoes to breed. Another example comes from two studies that linked malaria increases in the Bure highlands of Ethiopia to increased maize farming. There, the immature and aquatic stages of mosquitoes thrive on a diet of maize pollen, and more mosquitoes can mean more malaria.
"A major future challenge will be to link up what happens with mosquitoes and parasites at the household level with long-term climate change scenarios at the continental scale," Koenraadt said.
The spread of malaria in highlands is of great concern to those who work to contain the disease. But understanding the many factors that influence the spread of highland malaria could help with efforts to co
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