Aedes aegypti on the comeback

When the rains returned after the long (ten week) drought we had starting at Christmas, it took a couple of weeks for the mosquito populations to return – and return they did in force. Part of the reason for this is how mosquitoes lay their eggs – on the sides of breeding sites, so that they only hatch after a rain. This means that in a drought, the eggs build up in huge quantities – and when the rains come, they all hatch at once.

Aedes aegypti
Front view of Aedes aegypti showing the characteristic white dots in front of the antenna.

Importantly, some of us taking part in the iNaturalist project are observing a return of the Aedes aegypti. You may know that this mosquito is a very aggressive biter, and a very efficient vector of disease, much more so than the more common Aedes albopictus. In Kehena, I only caught one aegypti in the months from November through to March when the rains returned. During that time, I caught dozens of albopictus. Now, I can catch aegypti regularly. Clearly, the drought has tipped the scales towards aegypti, at least for a while. In fact, this is kind of what is expected based on their biology.

Another volunteer, Don Kephart, up in the Kohala area lives in an area dominated by aegypti (there are no albopictus!) and he says the population is the largest he’s seen in years.

This is important information, because aegypti are much better vectors of diseases like dengue, zika, chickungunya, etc. If we have established populations of aegypti we are at a greater risk of disease outbreaks than if we do not have these populations. Making sure the DOH knows where these populations are will help them in their response to future outbreaks. Who would have guessed there was a resident population of aegypti on the “wet” side? There were reports of aegypti here last in 2002. And we have also seen them this year near Kalapana (another volunteer, Devin has caught them there).

It would be great to get more observations of these mosquitoes on the leeward side of the island. If you are interested in helping, we can teach you how to ID mosquitoes and maybe even give you some equipment to help (such as a macro lens for your smartphone).

Here is a link to my recent aegypti observation on iNaturalist.

Just contact me!   mosquitotraps at hotmail dot com or on FB.