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Warming temperatures are spreading malaria to higher elevations

It used to be that higher altitudes and cooler latitudes provided some protection against the world’s most persistent killer: Malaria. With global warming comes a larger playing field for the Plasmodium falciparum blood parasite. This parasite is carried by the anopheles mosquito and it is the most important parasite in the world. Malaria was confined to hotter, lower lying parts of the world, but according to a March 6 BBC News article, the parasite is spreading to higher altitudes in African and Latin American nations.

Anopheles gambiae mosquito
Muhammad Mahdi Karim at Wikimedia commons

In 2012, there were 207 million bouts of malaria that caused an estimated 627,000 deaths. Malaria is particularly hard on children who live in African nations as they account for most of the deaths.

There are two signs that warmer temperatures are allowing the spread: increased infections in populations that moved to higher altitudes and signs of infection in areas that were once free of Malaria.

Prof Mercedes Pascual was part of a team of ecological scientists from the University of Michigan. The team studied Malaria rates in Columbia, South America and Ethiopia. They used existing records from the Antioquia region of western Colombia and the Debre Zeit area of central Ethiopia.

According to a March 6 University Herald article, the Ethiopian records dated from 1993 to 2005. The Columbian records covered from 1990 to 2005. The scientists focused on densely populated highland areas in both countries.

Prof Pascual concluded that,

“We have estimated that, based on the distribution of malaria with altitude, a 1C rise in temperature could lead to an additional three million cases in under-15-year-olds per year,"

This is because the records showed the spread and increase during years of higher temperatures and a corresponding decrease during cooler years. The important thing to know about climate change is that it is not measured from year to year, but over as many decades as possible.

As for malaria, the important goal is to attack the disease at the perimeter of newly infected areas, where it is easier to control. Once established, malaria is very difficult to control. Finally, human populations, especially children, are at greater risk when they have no previous exposure to malaria. The key to controlling the mosquito population is aggressive abatement and control.

As for the rest of the globe, a February 2010 article in Nature indicates a more positive estimate from the ecological science community. This is because mosquito control and abatement programs are becoming more effective and aggressive in industrialized and urban habitats.This is especially so in the U.S. where West Nile virus is of great concern. The Nature article had promising news,

“Predictions of an intensification of malaria in a warmer world, based on extrapolated empirical relationships or biological mechanisms, must be set against a context of a century of warming that has seen marked global declines in the disease and a substantial weakening of the global correlation between malaria endemicity and climate.”

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