Due to climate change, mosquitoes that transmit malaria are spreading to other regions

diseases transmitted by mosquitoes they kill more than a million people and infect up to 700 million each year, or nearly one in ten people. And it will intensify as climate change on Earth continue and worsen.

It’s just that as the planet gets warmer, the mosquito season is getting longer. Thus, one of the deadliest creatures in the world, due to its ability to transmit disease, will expand its geographic range to new regions and reappear in areas where its numbers had been declining for decades.

Extreme weather conditions such as droughts, heat waves, floods and rainfall are increasing in severity and regularity around the world. All of this creates favorable conditions for mosquitoes to breed and could contribute to the spread of their viruses to higher latitudes and altitudes.

Based on data spanning the past 120 years, scientists from Georgetown University Medical Center (USA) found that mosquitoes responsible for transmitting malaria In Africa they are extension deeper in the south of Africa and at higher altitudes than previously recorded.

The researchers estimate that the populations of anopheles mosquitoes sub-Saharan Africa have gained an average of 6.5 meters in altitude per year, and that the southern limits of their range they moved 4.7 kilometers per year south of the equatoras published in the magazine Biology Letters.

“This is exactly what we would expect if climate change helped these species reach the coldest regions of the continent,” said Colin Carlson, assistant research professor at the Center for Global Health Sciences and Security at the University of California. Medical Center. University and lead author of the study. If mosquitoes are spreading to these areas for the first time, it could help explain some recent changes in malaria transmission that have otherwise been difficult to trace to climate. »

The conclusion of the research is that the mosquitoes that transmit malaria in Africa are spreading to other regions due to climate change. The world is at least 1.2 degrees Celsius warmer than it was in pre-industrial times. As the planet warms, plants and animals, especially invertebrates, seek cooler temperatures., either moving to higher altitudes or approaching the poles. In 2011, scientists estimated that terrestrial species were moving upwards at a rate of 1.1 meters per year, and towards more polar latitudes at 1.7 km per year, making the movement of mosquitoes a relatively rapid change. in comparison.

Ticks that transmit Lyme disease, for example, are greatly expanding their range in the northern United States. Bats are also on the move, and with them the diseases they transmit, such as rabies. The researchers focused on mosquitoes of the genus Anopheles both for their ability to spread malaria and for the existence of a unique historical data set that tracks their movements. Carlson noted that other species are likely to move similarly, but future research will need to get a sense of what’s happening in different regions or with different diseases to get as complete a picture as possible.

“We tend to assume these changes are happening all around us, but the evidence base is quite limited,” Carlson said. If we rethink the biomonitoring of life on a warmer planet, much of it will have to be monitoring the movement of animals. »

And he noted that his team learned a lot about long-term changes in biodiversity from historical public health records. “We know very little about how climate change affects invertebrate biodiversity. Public health gives us a rare window into how certain insects might thrive in a changing climate, even if it’s bad news for humans.”

Climate change also increases the risk of mosquito-borne diseases in less obvious ways, said Dr Katie Anders, epidemiologist and director of impact assessment at the Global Mosquito Program (WMP): “For example, when households store water in response to drought, it can increase local mosquito breeding sites and disease risk. Land use change can lead to migration to cities, increasing the risk of explosive outbreaks of dengue fever and other mosquito-borne diseases.

Mosquito-borne diseases – already endemic in sub-Saharan Africa, Southeast Asia and Latin America – are recovering in populations in different parts of the world. The Early Warning System for Mosquito-borne Diseases (EYWA) shows an upward trajectory in Europe, with malaria cases increasing by 62% and dengue, Zika and chikungunya by 700%. Extreme flooding in Germany just last year showed an increase in mosquito numbers up to ten times higher than usual estimates.

South Australia is another recent example of mosquitoes expanding into new geographic areas. The region is currently facing its first major outbreak of Japanese encephalitis, a mosquito-borne infection most commonly found in rural Southeast Asia and the Pacific Islands. Scientists believe climate change has created a potential “perfect storm”, allowing the virus to move south and establish itself in the country.

Although there are more than 3,000 species of mosquitoes worldwide, the most serious diseases like dengue fever, chikungunya, Zika and yellow fever are only transmitted by two: Temples of the Egyptians there Aedes albopictus (also known as the Asian Tiger Mosquito). Dengue fever, the world’s fastest-spreading mosquito-borne disease, is estimated to infect more than 390 million people a year, with more than half of the world’s population currently at risk.

In Argentina, the Ministry of Health issued an alert a few weeks ago due to the increase in cases of dengue fever and chikungunya, due to the growth of these diseases in neighboring countries such as Paraguay and Brazil. This is how we avoid the sad record that Argentina registered in the 2019-2020 season, with nearly 60,000 cases.

A recent study, conducted by the London School of Hygiene and Tropical Medicine (LSHTM), predicted that more than eight billion people could be at risk of malaria and dengue fever by 2080. The research found that the increase in global temperature could lengthen annual transmission seasons. over a month for malaria and four months for dengue over the next 50 years. This is based on projections of population growth of 4.5 billion over the same period and a temperature increase of 3.7°C by 2100.

An article published in Nature reviews It further reports how increased global connectivity presents unique risk factors for the spread of infectious diseases, allowing pathogens (microorganisms that can cause disease) to travel farther and faster than ever before.

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