New maps can guide prevention efforts
FRISCO — Warmer global temperatures are enabling the spread of disease-carrying mosquitoes, putting millions of people at risk, Oxford University researchers say.
The scientists recently created the first global distribution maps of two species of dengue and chikungunya-carrying mosquitoes, showing a rapid expansion in parts of the US, Southern Europe and China during the past 10-15 years.
The study identifies areas not yet populated by the insects that are suitable for their survival, for example in Europe. The findings are published in the journal eLife.
“Given the lack of a vaccine or any antiviral treatment for either virus and the debilitating pain they both cause, knowing where the mosquitoes are spreading to and where they might turn up next is crucial for helping to protect communities,” said first author Moritz Kraemer. This is especially true in Africa, where records are sparse.
Urban areas worldwide are particularly susceptible to the spread of the yellow fever mosquito, Aedes aegypti, which also carries the viruses and lays its eggs in artificial containers such as buckets and discarded tyres. Concentrations of both mosquitoes are particularly high in Brazil, China, Taiwan and the US, though infection via Ae. Aegypti is not so widespread in the US.
Dengue fever is the world’s most common insect-borne virus, causing 100 million annual infections and leaving almost half of the world’s population at risk. The invasion of chikungunya into the Americas has already caused over one million cases of disease. The maps are also relevant to yellow fever, though infections from this virus are already on the decline.
Temperature is key to the survival of both species and they are mainly found in the tropics and subtropics. However, the tiger mosquito Aedes albopictus can overwinter in colder locations by becoming dormant. This allows it to extend the margins of its range. Once introduced via major shipping or travel routes, the mosquitoes spread quickly over land.
The scientists created the maps from records that include collections of the insects from national entomological surveys and published resources in many languages.
“We have made our data openly available so they can be used straight away to help protect people against these viruses about which we still know so little and have so few defenses,” said lead author Professor Simon Hay,
The paper ‘The global distribution of the arbovirus vectors Aedes aegypti and Ae. albopictus’ can be freely accessed online at http://dx.doi.org/10.7554/eLife.08347.