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Malaria Risk Influenced by Daily Temperature Variations

A team of researchers that includes Matthew Thomas, professor of ecological entomology, and Justine I. Blanford, research associate in geography for the Penn State GeoVISTA Center, believes their results may also apply to environmentally temperature-dependent organisms other than the malaria parasite. The results of their study, funded by the National Science Foundation, are published in the current issue of 
Scientific Reports.

“Temperature is a key driver of several of the essential mosquito and parasite life history traits that combine to determine transmission intensity, including mosquito development rate, biting rate, and survival of the parasite within the mosquito,” said Blanford.

mosquito

The team chose four locations in Kenya representing four different climates, including warm, arid conditions and cool, upland conditions. They looked specifically at the extrinsic incubation period (EIP), the length of time it takes for a parasite to complete development inside a mosquito from initial acquisition through an infected blood meal to transmission to a host via another blood meal.

The researchers estimated hourly temperatures using data on minimum monthly and maximum monthly temperatures, which could then be compared to the mean monthly temperatures usually used to determine malaria risk.

They found that EIP measurements based on mean monthly temperatures and mean daily temperatures were similar in all cases. For measurements based on hourly temperatures, the EIP was significantly longer in warmer locations.

Applying this method to other locations in Kenya, they found that “mean temperatures overestimate parasite development rate under warm conditions, provide a good approximation of growth under intermediate conditions, and underestimate development under cool conditions.”

According to the researchers, daily temperature dynamics could have marked impacts on many species, affecting understanding of both current ecology and the expected responses to future climate change.

A’ndrea Messer