According to a new study published in Biology Letters, Anopheles mosquitoes from Africa have moved southward on average at a rate of almost three miles per year. A further indication that rising temperatures may already be driving these disease vectors to new locations and doing so more quickly than some other land species is the mosquitoes' ascent to higher altitudes of over 2,200 feet.
The study's principal investigator, Colin Carlson, a global change biologist at Georgetown University's Center for Global Health Science and Security, said, "These guys are trucking across the continent." According to him, scientists have discovered that land species typically gain about 3 feet of elevation and about a mile of latitude each year. He claimed that the malaria-carrying mosquitoes move considerably more quickly than that.
In Africa, malaria is a serious and often fatal issue. The continent has warmed by 0.9 degrees Fahrenheit (0.5 degrees Celsius) or more over the last 50 to 100 years, and scientists have long predicted that climate change could spread the disease to new regions of the continent. But for scientists, it has been difficult to conclusively link this increase to increased malaria transmission.
According to Carlson, that simplicity is effective in demonstrating how mosquitoes are now present where they previously weren't. However, the study cannot conclusively state whether these changes resulted in an increase in malaria cases or exclude the possibility of other contributing factors, such as variations in how mosquito populations were sampled over time or modifications in human behaviour that might have aided in the disease's spread.
Additionally, the study was unable to evaluate changes in the rate of range expansion. According to Carlson, many temperature changes in Africa weren't really noticeable until between the 1950s and 1980s, suggesting that the mosquitoes may have relocated much more recently. Although we still need to investigate these issues, the fact that mosquitoes are emerging in new locations provides us with useful information, he continued. We should work to eliminate mosquitoes before they establish a presence.
On the front lines of this expansion, better monitoring and vector control could stop the disease in its tracks. Malaria prevention measures, such as treating breeding areas or using mosquito nets treated with an insecticide, can significantly lessen the disease's effects.
According to Carlson, in the 1900s, 40% of children under the age of five had malaria at any given time. Between 2000 and 2015, "that percentage fell to 24%." It is crucial to implement these tactics in areas where malaria isn't currently an issue but potentially could be, he said.
It's not just malaria that mosquitoes can spread; as a result of climate change, many insect vectors are likely to continue spreading disease to new regions. In addition to malaria, many other diseases will be impacted by the effects of climate change, according to Felipe Colón, technology lead at Wellcome, a charitable foundation that funds climate research.
"As the planet continues to warm, it will be more susceptible to climate-sensitive diseases like cholera, Zika virus, and dengue fever. Accordingly, many regions are already experiencing catastrophic health effects, he said. "It is essential that this issue receive more attention so that we can prepare for and counteract these effects."
REFERENCE:
Colin J. Carlson, Ellen Bannon, Emily Mendenhall, Timothy Newfield and Shweta Bansal, https://doi.org/10.1098/rsbl.2022.0365