Fluctuations in temperature during the day, not just the average monthly temperature, should be considered when it comes to studying the impact of climate change on malaria, according to a new research.
The study showed that daytime temperature fluctuations greatly alter the incubation period of malaria parasites in mosquitoes and alter transmission rates of the disease.
"Most studies use average monthly temperatures to study the impact of climate change on the global malaria burden," said Matthew Thomas, professor of entomology, Penn State.
"But mosquitoes and the malaria parasites developing within them do not experience average temperatures; they are exposed to temperatures that fluctuate throughout the day," he added.
According to him, the key to understanding the transmission of malaria lies in the time parasites take to incubate within a mosquito.
In areas of high malaria transmission, the parasites take between 10 to 14 days to mature and become infectious.
But almost 90 percent of female mosquitoes-which transmit the disease-die within 12 days. So even a tiny increase or decrease in the parasites' incubation period can greatly alter the number of mosquitoes available to transmit malaria.
Thomas and colleagues used a thermodynamic model to estimate the growth of malaria parasites during 30-minute intervals while temperatures fluctuated.
They found that under warmer conditions the daily temperature fluctuation effectively slows down the parasites' growth, while under cooler conditions the parasites grow more quickly because at least for part of the day they experience a warm temperature.
"We measure how parasite growth rates accumulate over 24 hours and subsequently over days. And if you add up the effects from parts of the day being very cool and parts of the day being very warm, you get a different outcome than if you simply use the mean monthly temperature," Thomas said.
To test their model, Thomas and his colleagues looked up average monthly temperatures and change in daytime temperatures for 1987 through 2005 during the main malaria transmission season at Kericho, a site in the Kenyan Highlands.
The findings appear in the Proceedings of the National Academy of Sciences.