New maps predict which regions will be most at risk of malaria due to global warming

Mark Smith, Leeds University And Chris Thomas, Lincoln University

Estimated 228 million About 93% of malaria in the world is in Africa every year. This rate is about the same as the 405,000 malaria deaths worldwide.

Therefore, great efforts are made to provide detailed information. Map of current malaria cases In Africa, such maps are essential for controlling and treating infections and therefore predict which regions will be more susceptible in the future. Understanding the implications of global warming for malaria risk across the continent is also important because mosquito populations can respond quickly to climate change.

Published a new set of maps at Natural communication It provides the most accurate picture of where in Africa climate change is or is not suitable for malaria infection.

Screenshot of Nature Communications

The malaria parasite breeds where it is warm and moist. Temperature controls several parts of the infection cycle, including mosquito lifespan, growth rate and bite rate.

If the temperature is too high or too low, malaria parasites or mosquitoes that transmit parasites between humans will not survive. This appropriate temperature range is relatively well established by field and laboratory studies and forms the basis for current predictions of the effects of climate change on malaria.

However, surface water is equally important as it provides a habitat for mosquitoes to spawn. Watering large rivers does not provide a suitable larvae habitat for African vector mosquitoes, but the associated irrigation schemes and ponds and puddle may form somewhere in the landscape, Small water bodies in the region, such as dike ponds and flood plains, are very productive.

However, it is difficult to estimate future surface water. It is difficult to accurately predict how many years of aquaculture and irrigation will occur as river water levels change with the seasons and ponds and puddles appear and disappear.

Previous model For the suitability of malaria transmission across Africa, a simple total monthly precipitation was used to estimate the amount of habitat available to mosquitoes. Instead, we investigated the formation of water bodies in more detail. When these hydrological processes are included in the model, different patterns are observed both now and in the future.

Beyond the rainfall

In the tropics, mosquitoes breed in heavy rains, and the area is probably suitable for malaria transmission. If this place is also on the right Temperature range, It is climatically suitable for malaria infection. There may be no infection now-perhaps because the disease was eradicated there-but the climate is suitable.

In general, this approach works well, especially across Africa. But that’s not really how surface water works. In extreme cases, most areas of the Nile have little rainfall, A lot of mosquitoes You can see that malaria was widespread in ancient Egypt.

Rainwater infiltrates the soil, evaporates back into the atmosphere, is absorbed by vegetation, and of course flows downhill into rivers and rivers. A new approach was needed because rainfall does not always match the amount of water remaining on the surface.

More complex patterns

In a recent survey, Continental-scale hydrological model Estimate the availability of surface water. This highlighted a much more complex and arguably more realistic pattern of hydroclimatic suitability. Unlike the rainfall-based approach, our model highlights the river corridor as a potential focal point of yearly infections.

Our work shows that some areas that were very clearly lacking from previous models are actually suitable for malaria infection. This includes the Nile system, and corroborated by historical observations of malaria outbreaks, the current estimate of infectivity extends significantly to the northern coast of Africa.

Similarly, the Siberian Niger and Senegal rivers, the Webegjuba river and the Webbisha Beeley river are beyond the geographical range previously estimated to be climatically suitable. This is especially important because the human population tends to concentrate near such rivers.

Differences can be seen when comparing the forecasts of future hydroclimate models with those from previous rainfall threshold models. Both suggest only very small changes in total area suitable for the entire continent by 2100. The most extreme global warming scenario.. However, when hydrological processes were taken into account, large shifts in hydroclimatically relevant areas were observed and the places where changes were predicted were very different.

For example, in South Africa, rather than focusing on improving suitability in the eastern part of the country, centered around Lesotho, the suitability of the suitability along the Caledon and Orange rivers to reach the border with Namibia will be reduced. We anticipate that the areas for improvement will expand. Especially in Botswana and Mozambique, the loss of suitability due to the effects of drought throughout southern Africa is no longer seen.

Conversely, the projected reductions across West Africa are more pronounced. The biggest difference is South Sudan, and our hydrological approach estimates that malaria’s suitability will decline significantly in the future.

Watering landscapes in a realistic manner maps very different patterns of malaria infection suitability, both today and in the future. But this is just the first step.

There are many more things we can do to incorporate state-of-the-art hydrological and flood models into malaria suitability estimates and early warning systems for local malaria epidemics. Today, the exciting challenge is to develop this approach at the regional scale that public health institutions need to support the fight against disease.

Mark Smith, Associate Professor of Water Research, Leeds University And Chris Thomas, Global Professor of Water and Planetary Health, Lincoln University

This article is reissued from conversation Under Creative Commons license. Read Original work..