Maps to anticipate the global spread of mosquito vectors and how to control them.
Dengue, zika and yellow fever cause burden across the world and the areas where outbreaks occur are continuously expanding. Their future distributions crucially depend on where the mosquitoes that transmit these viruses, Aedes aegypti and Aedes albopictus spread over the coming decades. We have taken the steps to model their likely geographic distributions using climate change scenarios, human movement, and settlement data, today and in the future.
Our main goal in this work was to quantitatively understand how Aedes aegypti and Aedes albopictus, the most important arbovirus vectors, spread historically and use these insights to better predict their future distributions.
Aedes albopictus mosquito. Picture Credit: Francis Schaffner.
These mosquitoes don't fly very far (approximately <100m) but have spread to all continents around the world (except of course Antarctica). How did they do that? Usually they come as blind passengers on large ships that cross the oceans from areas endemic to these mosquitoes to areas where they were not present before. Eggs then may hatch and the mosquitoes can flourish in these new areas. However, the areas where the mosquitoes arrive must have similar climatic conditions.
Transportation pathways of Aedes mosquitoes. Credit: Sharon Isern.
Now, once the mosquitoes have arrived in these new areas they are transported via other means: for example on trains, smaller boats, via highways on trucks or in private cars. The more traffic, the more likely the vectors spread to new areas. This continental expansion process is well described to happen along the highway network in the United States (south to north) and from Italy across to France and over the Alps to Germany.
With an international team of researchers we tabulated historic records of both species, used statistical techniques to model their process of spread, and based on that predicted forward how they may spread. All of that is done at a spatial resolution that is relevant for intervention strategies (5x5km) and globally comprehensive. This work is published today in Nature Microbiology. We find that they will continue to expand under conditions of accelerated urbanization and climate change. Interestingly, both species will expand but urbanization is a much bigger driver of Ae. aegypti spread compared to Ae. albopictus.
Predicted distribution of Aedes aegypti in 2050 at a 5x5km resolution under the medium climatic scenario RCP6.0 where emissions are predicted to peak in 2080.
With this new work, we can start to anticipate how the transmission of diseases like dengue and Zika might be influenced by a variety of environmental changes. Incorporating this information into future scenarios of risk can help policymakers prepare for and predict health impacts, to help guide strategies to limit the spread of these mosquito species, an essential step to reduce the disease burden.
Authors: Moritz Kraemer