Monday, 20 July 2015

Hate mosquitoes, this work will help you avoid them


My two most recent posts to this blog have had an, admitted unplanned, theme of looking at viruses spread by Aedes mosquitos (Dengue and Chikungunya). Shortly after posting my last article, research was published which analysed the global distribution of the two Aedes species responsible for spread of these, and other viruses. So it seemed like a logical way to conclude this mini-series of posts. (I highly recommend going to the hyperlink for the paper as there are some cool maps to look at at the bottom).

Aedes mosquitoes are limited to where they can live by multiple factors, predominantly temperature and rainfall. The insects need high temperatures, but also need rainfall as they lay their eggs in water. These factors help to limit the habitable zone of Aedes largely to the topics. However, with global warning, the regions in which the mosquitoes can survive and spread is increasing, causing concern about the viral diseases they can transmit.

The study, which was published in the journal eLife, aimed to establish models to predict the global regions that Aedes egypti and albopictus could live. The models were based on real world data gathered by capturing mosquitoes across the globe. In total, 19,930 A. egypti and 22,137 A. albopictus mosquitoes were captured. Most of these were captured in Asia, 60% of the A. egypti and 75% of the A. albopictus captures. The Americas came in a comfortable second for the highest proportion of captures. This suggests that most of the mosquitoes currently reside in tropical parts of Asia and the Americas. Building on this knowledge, and factoring in climactic conditions that impact mosquito survival, models were generated to predict potential areas that the mosquitos can live.

Using these models, we now have more information about areas that could be at risk of the viral diseases carried by the mosquitoes. For instance, Mexico is predicted to have ideal conditions for the two mosquito species, even though none were captured there during the course of the study. In Europe, captures suggested that Greece and Italy have an increasing presence of the mosquitoes, and that while none were captured there, Spain, Portugal and much of south-eastern Europe have good conditions for spread.
A large part of this work is predictive, but it is based on a lot of data both on capture of mosquitos and climactic conditions. The knowledge that has been generated about current regions in which the mosquitoes spread, and the regions with potential, will direct public health work. Keeping an eye on whether the mosquitoes become established in Spain for instance, will help people take better precautions and look to limit the spread of viral diseases such as Dengue and Chikungunya. Forewarned is forearmed as they say.

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