New research show impacts of warming temperatures on mosquitoes

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April 26, 2024

PHOTO: UF/IFAS

Showing a bursting oocyst with sporozoites exiting on the surface of a midgut of an Anopheles gambiae s.s. mosquito. PHOTO: UF/IFAS

New research shows the impacts of warming temperatures in mosquito species carrying malaria-causing parasite.

In 2022, an estimated 249 million malaria cases killed 608,000 people in 85 countries worldwide, including the U.S., according to the World Health Organization. Florida was one of the states with reported cases last year.

Malaria continues to pose a considerable public health risk in tropical and subtropical areas, where it impacts human health and economic progress.

In “Estimating the effects of temperature on transmission of the human malaria parasite, Plasmodium falciparum,” a study published in the journal Nature Communications, researchers at the University of Florida, Pennsylvania State University and Imperial College combined novel experimental data creating an innovative modeling framework to examine how temperature might affect transmission risk in different environments

“In broad terms, scientists know that temperature affects key traits such as mosquito longevity, the time it takes for a mosquito to become infectious after feeding on an infected host, and the overall ability of the mosquito to transmit the disease,” Dr. Matthew Thomas, a UF/IFAS professor and UF/IFAS Invasion Science Research Institute (ISRI) director, said in the news release. “But what might seem surprising is that these temperature dependencies have not been properly measured for any of the primary malaria vectors in Africa.”

PHOTO: UF/IFAS

A close-up image of matured oocysts on a midgut of a blood-fed Anopheles gambiae s.s. female mosquito. PHOTO: UF/IFAS

“Our findings provide novel insights into the effects of temperature on the ability of Anopheles gambiae mosquitoes — arguably the most important malaria mosquito in Africa — to transmit Plasmodium falciparum, the most prevalent species of human malaria in Africa,” said Eunho Suh, joint first-author with Isaac Stopard at Imperial College, and assistant research professor at Penn State, who conducted the empirical research as a post-doctoral student in Dr. Thomas’ previous lab.

The study involved several detailed laboratory experiments in which hundreds of mosquitoes were fed with Plasmodium falciparum-infected blood and then exposed at different temperatures to examine the progress of infection and development rate within the mosquitoes, as well as the survival of the mosquitoes themselves.

“The novel data were then used to explore the implications of temperature on malaria transmission potential across four locations in Kenya that represent diverse current environments with different intensities of baseline transmission, and that are predicted to experience different patterns of warming under climate change,” said Dr. Thomas.

The study supports previous research results in demonstrating that various mosquito and parasite traits exhibit intermittent relationships with temperature — and that under future warming temperatures, transmission potential is likely to increase in some environments, but could reduce in others. However, the new data suggest that parasites can develop more quickly at cooler temperatures, and that the rate of parasite development might be less sensitive to changes in temperature than previously thought.

The data also indicate that the successful development of parasites in the mosquito declines at thermal extremes, contributing to the upper and lower environmental bounds for transmission.

Combining these results into a simple transmission model suggests that, contrary to earlier predictions, the anticipated surge in malaria transmission, attributed to climate warming, may be less severe than feared, particularly in cooler regions like the Kenyan Highlands.

PHOTO: UF/IFAS

Showing a whole midgut of Anopheles gambiae s.s. mosquito with dozens of oocysts growing on it. PHOTO: UF/IFAS

“Some of the current assumptions on mosquito ecology and malaria transmission derive from work done in the early part of the last century. Our study is significant in highlighting the need to revisit some of this conventional understanding,” said Dr. Thomas.

“While the time it takes for a mosquito to become infectious is strongly dependent on environmental temperature, it also depends on the species and possibly strain of malaria and mosquito,” said Suh.

The comprehensive study and findings represent a significant step forward in understanding the intricacies of malaria transmission and paves the way for future research aimed at controlling malaria on a global scale, the researchers said. The same is true for other vector-borne diseases, such as dengue or Zika virus, added Suh.

“We need more work of the type we present in the current paper, ideally using local mosquito and parasite or pathogen strains, to better understand the effects of climate and climate change on transmission risk,” he said.

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About the Author

Ellen Wagner is a former digital editor for PMP magazine.

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