Climate change is opening up new habitats for malaria mosquitoes in Africa, study results suggest: In the past, they have been able to steadily expand their distribution areas, according to analyzes of data from the last 120 years. In highland regions, Anopheles mosquito populations increased in altitude by an average of 6.5 meters per year, and in the south of the continent they increased by 4.7 kilometers per year towards cooler latitudes. The advance fits with climatic changes in Africa and could explain the advance of malaria transmission into new areas over the past few decades, the researchers say.
The heat is spreading more and more in the direction of the poles and is also increasingly climbing to the higher altitudes of our planet: these consequences of climate change are making themselves felt in many places with various signs. One aspect is that certain animal and plant species can spread into areas where it was previously too cool for them. This can also affect creatures that are problematic for us. In the case of some animal disease carriers, territorial gains in the course of climatic changes have already been demonstrated.
Targeting notorious bloodsuckers
So far, however, there has been little information on one of the most important groups of these so-called biological vectors: To what extent climate change is contributing to a change in the distribution areas of the malaria-carrying Anopheles mosquitoes in Africa has so far been difficult to assess. Although the continent is generally considered warm enough, there are areas in the south and in high-altitude regions where it gets too cool for these warmth-loving insects. But other factors can also have a strong influence on the spread of the bloodsuckers, which is why the effect of the individual aspects is difficult to grasp.
In order to trace territorial developments and the possible influence of climate change on the Anopheles mosquitoes, the scientists working with Colin Carlson from Georgetown University Medical Center in Washington DC have now collected and evaluated extensive data dating from the period 1898 to 2016 . This is information about the type and locality of malaria-carrying representatives of the Anopheles mosquito from sub-Saharan Africa, which was generated by insect and malaria researchers over the last 120 years or so.
Land gains in the highlands and south
As the team reports, there is a steady process of spreading in many areas, both at high altitudes in mountainous and highland regions and in the south of the continent. The researchers’ estimates show that the Anopheles mosquito populations were able to “climb” an average of 6.5 meters per year during the study period. According to the calculations, the shifting of the distribution limits to the south progressed at about 4.7 kilometers per year. As they explain, the patterns of spread suggest that the creeping climatic changes are linked to this advance. This is because changes in the distribution patterns of Anopheles mosquitoes appear to be consistent with estimates of the local progression of climate change in Africa. “That’s exactly what we would expect if climate change were helping these species reach colder parts of the continent,” says Carlson.
According to the researchers, the new evidence also sheds light on the extent to which climate change may affect the burden of malaria disease in Africa. “Information on the evolution of mosquito spread may help explain some recent changes in malaria transmission that are otherwise difficult to attribute to climate,” says Carlson.
However, as the team concludes, more detailed studies are needed to substantiate the evidence for the advance of malaria mosquitoes in the wake of climate change. “Further research should confirm the extent to which climate change underlies the shifts,” the researchers write. They also encourage using their methodological approach in the case of other disease vectors. “We still know too little about how climate change is affecting certain animals. Research related to health issues can give us insights into how problem insects thrive in a changing climate,” Carlson said.
Source: Georgetown University Medical Center, Article: Biology Letters, doi: 10.1098/rsbl.2022.0365