Climate-change effects on malaria risk

February 3, 2012 By Adele Rackley
Climate-change effects on malaria risk

A new study suggests that climate change, driven by greenhouse-gas emissions and land-use changes, will cause patterns of malaria infection to change over the next 50 years.

The study combined simulations of mosquito biting rates and rates with a detailed regional model, to predict changes in the pattern of malaria infection across a large area of Africa up to 2050.

The news is good for some and bad for others. The spread of malaria is predicted to decrease over most parts of tropical Africa because of likely increases in and reduced . But epidemics are projected to move south in the sub-Saharan Sahel region, and in much of of the disease are likely to increase.

In particular the study highlighted the sensitivity of upland areas, where a change of just 2°Celsius could put previously malaria-free regions at risk of epidemics.

"This is one of the first studies to use such a high-resolution climate model across such a wide swathe of Africa," says Dr. Andrew Morse from the University of Liverpool, one of the authors of the research, published in Environmental Health Perspectives.

Malaria flourishes in warm, humid environments, so surface temperature and rainfall are the two most important natural factors that influence where it will strike and how quickly it's likely to spread.

Climate-change effects on malaria risk
Malaria parasites are transmitted to humans by mosquitoes.

The combined weather-disease model showed how temperature and rainfall might change under two climate scenarios using different levels of greenhouse-gas emissions, and also with likely changes to land-use – for example when forests are cleared to make way for crops.

The human effects on climate through land-use change are ignored by many climate models. But they can have a significant effect on local climate – clearing land of natural vegetation, for example, causes local temperature to rise and reduces rainfall.

The model predicts changes in both the geographic occurrence of malaria and the intensity of transmission.

"Where malaria occurs every year it's already a public health issue," explains Morse. "But we also interested in areas that might be newly at risk of epidemics."

When a malaria epidemic strikes it is in an area where people have low immunity and the disease is more likely to affect people of all ages. So knowing what areas might become at risk in future would make prevention and treatment more effective.

Though it's unrealistic to target malaria treatment programmes as far ahead as 2050, these long-term predictions would be useful for strategic land-use planning, for example where governments are considering developing particular areas or where populations are shifting from rural to urban centres.

One of the benefits of modelling trends at such a small scale is that the researchers can start to narrow down the timescales within which malaria infection patterns could change in particular areas, rather than making general statements. So the next step is to identify which altitude ranges or lowland areas are likely to be affected in a particular ten-year window – information which will be much easier for decision-makers to work with.

The researchers emphasise that other variables not included in this study, like improved prevention and treatment, might in practice counteract the effects of climate on . Indirect effects of on malaria might be important too; for example the effects of a warming climate on agriculture might cause people to migrate to urban areas, and this would affect transmission rates.

"This model doesn't include human interventions," says Morse, "but having the two climate scenarios and the land-use information shows us how the climate risk may impact on transmission patterns in the future."

More information: Ermert V, Fink AH, Morse AP, Paeth H, 2011. The impact of regional climate change on malaria risk due to greenhouse forcing and land-use changes in tropical Africa. Environ Health Perspect 120:77-84. doi: 10/1289/ehp.1103681

Related Stories

Recommended for you

Antibody found that fight MERS coronavirus

July 28, 2015

(Medical Xpress)—An international team of researchers has found a MERS neutralizing antibody—a discovery that could perhaps lead to a treatment for people infected with the virus. In their paper published in Proceedings ...

Experimental MERS vaccine shows promise in animal studies

July 28, 2015

A two-step regimen of experimental vaccines against Middle East respiratory syndrome (MERS) prompted immune responses in mice and rhesus macaques, report National Institutes of Health scientists who designed the vaccines. ...

Can social isolation fuel epidemics?

July 21, 2015

Conventional wisdom has it that the more people stay within their own social groups and avoid others, the less likely it is small disease outbreaks turn into full-blown epidemics. But the conventional wisdom is wrong, according ...

Lack of knowledge on animal disease leaves humans at risk

July 20, 2015

Researchers from the University of Sydney have painted the most detailed picture to date of major infectious diseases shared between wildlife and livestock, and found a huge gap in knowledge about diseases which could spread ...

IBD genetically similar in Europeans and non-Europeans

July 20, 2015

The first genetic study of inflammatory bowel disease (IBD) to include individuals from diverse populations has shown that the regions of the genome underlying the disease are consistent around the world. This study, conducted ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.