Could malaria be worsened by climate change?

Malaria is a serious public health issue with around 229 million cases worldwide (in 2019). The most vulnerable groups (children and pregnant women) cause the vast majority of deaths. 

Malaria is caused by the Plasmodium parasite. Plasmodium reproduces inside the Anopheles mosquito and the mosquito acts as a vector for transmission of the virus between human hosts. A pregnant female mosquito will feed on a human in order to gain enough nutrients for the development of their embryos. Once they feed on an infected individual they pass the Plasmodium parasite into their own bodies. There the parasite replicates and travels to the salivary glands of the mosquito so that when the mosquito bites a second person, they inject the parasite into them. Inside the human host the parasite travels to the liver and red blood cells causing damage. The lifecycle of the parasite relies heavily on the mosquito and without it there would not be a way for the parasite to reproduce and transmit between humans. Thus, when there is a increase in the number of mosquitos there will be an increase in the cases of malaria. 

Photo Credit: YourGenome

Climate change increases the spread, intensity and distribution of malaria by making more geographical regions habitable for mosquitos. In 1975, malaria was eradicated in Europe by better socio-economic conditions, better health care and improved insecticide spraying. However, climate change could cause a return of malaria cases in these areas once again. There are still many countries that are are impacted by malaria epidemics now, specifically in Africa, Asia and Latin America. Climate change could worsen the cases in these regions before it has even gotten better. 

The mosquito that takes blood must be a pregnant female so many eradication programmes have focused on removing breeding grounds for mosquitos. The way that mosquito’s breed is on open, still water such as lakes and puddles. As a result of climate change there is an increased amount of heavy rainfall, providing water and good breeding conditions. On the other side of the spectrum, droughts may turn rivers into strings of pools that don’t flow creating still water, ideal breeding grounds. Some scientists have argued that, climate change could help reduce the number of mosquitos. Heavy rainfall and extreme weather has been known to wash out the breeding sites. So some effects of climate change could help reduce malaria transmission but the economic and social effects of such extreme weather on causing floods and ruining public infrastructure outweighs the potential it does have for reducing mosquito breeding sites.

Furthermore, temperature increases could cause people living at higher altitudes to be affected by malaria, where it had previously been too cool. The higher temperature allows the parasite and mosquito to reproduce faster. People living in these areas have also not previously been exposed to malaria so will have no natural protection from it like other individuals. In areas where malaria has been endemic, there is an increased level of people with sickle cell anaemia (a genetic condition that causes your red blood cells to be sickle shaped which does lead to certain medical/health problems of its own). Sickle cell anaemia causes an immunity to malaria because of the way the red blood cells are shaped which the parasite can’t survive and reproduce in. People in high-altitude areas will have no protection so if malaria effected those regions, the populations will have high morbidity and mortality rates. These rates are predicted to lead to 60,000 additional deaths per year due to malaria between 2030 and 2050, 15% increase in overall annual deaths from a preventable disease.

Photo Credit: KidsHealth
The current transmission of malaria but this could move more into the yellow and blue areas as climate change develops. Photo Credit: CDC.

The rate of climate change and malaria transmission seem to be linked which could cause alarm as temperatures rise and extreme weather patterns become more common. Africa is a main cause for concern because the rate of climate change and malaria are high in that region.

However, malaria is also not the only concern, other mosquito transmitted diseases such as Dengue and Rift Valley fever could see an increase. Climate change could have a major impact on public health, all the more reason to enforce pollution regulations faster and more efficiently. Scientists are still doing research into the effects of climate change on malaria but they predict it will cause an increase in cases and deaths.

Photo Credit: NRDC

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