Climate Change may lead to spread of malaria as mosquitoes migrate to newer regions: Study

By Vivek Saini 

If emissions continue to rise at the current rate, up to 8.4 billion people might be in danger from the two primary vector-borne diseases, Malaria, and dengue, by the end of the century, says a new study published in the Lancet Planetary Health.

With temperatures on a constant rise, many tropical species formerly restricted to the world’s warmest regions are anticipated to migrate to higher altitudes and move further away from the equator as temperatures increase. The spread of Malaria, one of the most deadly illnesses in the world that currently claims the lives of more than 600,000 people annually, may indicate that this is already taking place. 

How climate change affects diseases 

Malaria is one of the diseases most vulnerable to climate change among the transmissible ones. Climate change and malaria transmission patterns have been linked in research since the early 1990s, resulting in an increased risk of malaria infection. Climate change has allowed mosquito populations to grow and develop quickly, live longer, and persist in previously inaccessible locations, exposing more people to Malaria. According to the latest Synthesis Report of the Intergovernmental Panel on Climate Change (IPCC), mosquitoes will transmit diseases wider than ever before if climate change continues unabated. An additional 4.7 billion individuals may be in danger of mosquito-borne diseases such as malaria and dengue fever by 2070. 

Mosquitoes are cold-blooded insects that thrive in warm weather. Humans have warmed the Earth by more than 1 degree Celsius on average since the Industrial Revolution. Pathogens are on the move as climate change disrupts habitats and drives plants and animals to new locations. In North America, for example, the tick that causes Lyme disease is already making its way north into Canada.

Mosquitoes are wreaking havoc on more than just humans. Native songbirds in Hawaii are dying from an avian type of Malaria. Scientists predict that mosquitoes will move deeper into the islands’ mountains as temperatures rise until the birds have nowhere else to go.

The indirect impact of climate change 

Climate change has an indirect impact on Malaria and the direct effects (increasing temperatures and rain). Among these indirect consequences are the several socioeconomic factors that influence malaria risk. These indirect influences, however, are very unpredictable and, therefore, understudied. Extreme weather, such as tropical cyclones, storm surges, excessive rainfall, and flooding, is a suspected contributor. These extreme weather events can substantially influence people’s capacity to get diagnostics, medications, or vaccinations. Extreme weather events may also cause highways and other modes of transportation to be closed. This complicates the transportation of essential supplies, particularly to people in remote rural locations.

The WHO lists several ways that Malaria may be affected by climate change. For instance, if people with low immunity to Malaria move to malaria-endemic areas due to climate change, this might “lead to large-scale population displacement—and this, in turn, could lead to more malaria transmission in some places,” the health organization told The Lancet. Furthermore, according to the World Health Organisation, “food insecurity due to climate change will increase the risk of malnutrition, especially among vulnerable groups such as children under five and pregnant women, increasing their risk of severe disease and their chances of survival.”

Another indirect effect of climatic change on malaria transmission is a willingness to take preventative measures. Wearing long garments (e.g., long sleeves and long pants) and sleeping under mosquito netting at night are two of the most suggested precautions. Rising temperatures, on the other hand, can make these things considerably less desirable. Those who do not wear long sleeves, long trousers or use mosquito netting are at a significantly higher risk of being bitten. Furthermore, risk mapping uses historical patterns to evaluate risk and alert you when traveling to a malaria-risk area. However, as seasonal changes continue to vary from historical norms due to climate change, they may become less effective.

“Public health officials need to get everyone attuned to the reality that they should be using mosquito control, which means that if they are going to be outdoors,” especially at dawn and dusk, because the mosquitoes that can transmit malaria tend to bite then, “they absolutely need to be wearing mosquito repellent”, said Dr Aileen Marty, an infectious disease expert at Florida International University.

Growing global risks 

The study says that even if emissions are reduced, 6.1 billion people could still be harmed, making the estimated number at risk still very large. Most of those in danger in Africa, South-East Asia, and the Americas will be located in heavily populated urban centers. Ideal transmission weather will improve, especially in already-endemic tropical lowlands and urban areas.  

A large spread to temperate and higher elevations, where populations may have yet to be exposed to these illnesses and health systems are not equipped to handle them is also expected, as per the study. Local dengue infections that haven’t been brought over from formerly endemic nations are starting to appear in Europe. This could have significant economic and public health ramifications for countries with little prior experience handling these diseases. 

The population at risk for vector-borne diseases is projected to decline significantly when greenhouse gas emissions are restricted. However, research indicates that with the current emissions rate, we must plan adaptation actions for a warmer and more urbanized world and be ready for anticipated increases in vector-borne diseases in numerous places.

A problem that cannot be ignored 

Approximately 80% of the worldwide human population lives in an area where at least one vector-borne disease is present. These diseases are generally associated with poverty and inequality, and many are chronic, debilitating, and stigmatizing, further exacerbating the situation. Some formerly controlled diseases have spread and gradually ravaged once disease-free areas (for example, the African highlands) while resurging in locations where they had receded for decades over the last three decades. 

Vaccines and therapies for some of these diseases are limited and frequently unsuccessful. Insecticide resistance is also becoming more common. Furthermore, there are substantial fears that climate change would exacerbate vector-borne disease transmission and incidence, putting more people at risk worldwide. 

References:

1. https://www.who.int/news-room/fact-sheets/detail/malaria
2. https://www.un.org/en/chronicle/article/climate-change-and-malaria-complex-relationship
3. https://www.ipcc.ch/report/ar6/syr/downloads/report/IPCC_AR6_SYR_LongerReport.pdf
4. https://www.ipcc.ch/ar6-syr/
5. https://www.washingtonpost.com/graphics/2019/national/climate-environment/climate-change-world/?itid=lk_inline_manual_20
6. https://www.washingtonpost.com/climate-environment/2023/02/14/climate-change-malaria-mosquito/
7. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(23)01569-6/fulltext
8. https://malariajournal.biomedcentral.com/articles/10.1186/s12936-021-03718-x
9. https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(21)00132-7/fulltext
10. https://www.theguardian.com/us-news/2023/jul/06/malaria-us-mosquitoes-climate-crisis