Climate change can widen areas with conditions favorable to the proliferation of disease-transmitting mosquitoes such as malaria and dengue, but the evolution of these diseases also depends on non-climatic factors. A review published in the journal Science Advances, by researchers at Monash University, points to the need to reinforce prevention and control measures as the climate changes.
Malaria is caused by a parasite and is normally transmitted by the bite of infected female mosquitoes of the genus Anopheles. Dengue, in turn, is caused by a virus transmitted by mosquitoes of the genus Aedes. According to the researchers, around 300 million malaria cases and almost 400 million dengue infections are recorded worldwide each year.
As temperatures rise and rainfall patterns shift, the areas where climatic conditions can be favorable to the populations of these mosquitoes also expand. However, the relationship is not linear and varies depending on the season and the territory.
“As climate change raises temperatures and alters rainfall patterns, it broadens the areas with climatic conditions in which Anopheles and Aedes mosquitoes can thrive,” explains Toby Cumming, a researcher at the Health and Climate Initiative of the Monash School of Public Health and Preventive Medicine.
Although sharing some climatic factors, the evolution of the two diseases has followed different paths. “However, over the last century, during a period of unequivocal warming, malaria rates declined, while dengue rates increased,” the researcher notes.
The authors point to factors not directly related to climate that help explain this difference. In the case of malaria, mosquito control interventions and pharmacological treatments contributed to a significant reduction in transmission. Meanwhile, growing urbanization favored Aedes mosquitoes and, consequently, the spread of dengue.
The trajectory of malaria also cannot be discounted. Despite the long-term trend of reducing the disease, global incidence rose 8.5% in the last decade, according to the review.
“The recent trends in malaria and the rapid growth of dengue are both reasons for great concern, and we must intensify our prevention and control efforts,” says Cumming.
Prevention Combines Several Fronts
The review highlights the need for a response that combines public health measures with actions directed at environmental factors. Among the identified strategies are mosquito control, the use of vaccines, and the reduction of greenhouse gas emissions, with the aim of limiting global warming.
In the case of dengue, new prevention tools are emerging, including vaccines and vector control strategies. One such approach involves introducing the bacterium Wolbachia into populations of Aedes mosquitoes, reducing their ability to transmit the virus.
“Ultimately, our research reinforces the need for a coordinated approach that includes interventions to address the many climatic and non-climatic factors that contribute to the spread of mosquito-borne diseases,” concludes Cumming.
