Science News Archive

Grounding Mosquitoes

Researchers in Oxford and California have found a way to stop mosquitos from growing wings – keeping them grounded and stopping the spread of diseases like Dengue fever.

Writing in the journal PNAS, Luke Alphey and colleagues highlight how controlling the principal vector, the Aedes aegypti mosquito, can help to reduce the increasing problem of Dengue and dengue haemorrhagic fever.  Current vector control methods are simply not effective enough, and we’re now facing an estimated 50-100million new infections annually.

One promising method is to control the mosquito population by releasing sterile males – thus reducing the population in the next generation.   This is known as the Sterile Insect Technique, or SIT, and although it showed some promising results back in the 1970s, it’s not being used in any large scale programmes.  Another technique is to introduce a lethal or incapacitating trait into the females of the population, and as it’s the females who bite and spread disease, this is particularly appealing.

This new study is based on modifying the Aedes aegypti Actin-4 (AeAct-4) gene in such a way as to render the female mosquitoes flightless.  This gene is active in the pupae stage of the female mosquito, predominantly in the Indirect Flight Muscles.  The researchers created a modified insect where this gene is only properly expressed in the presence of tetracycline, through a method called the Tet-Off system.  In the absence of tetracycline, these insects reached maturity, but were unable to fly.

Allowing the insects to reach maturity unharmed is an important aspect – it means that the larvae can still develop and compete with other larvae, and then only the adult female – the one that causes all the problems – is affected.  This also means that, rather than having to rear and release swarms of modified males, we can transport and release modified eggs.  As the eggs can be stored and stockpiled, this should mean that any control programme can start with a far bigger push than if we are relying on the maximum mosquito-rearing capacity of a lab.

The eggs will hatch, and the females will be, essentially, killed off immediately – they will be unable to feed, avoid predators or find a mate.  The males, however, should then mate with non-modified females, passing the flightless mutation on to the next generation and rapidly reducing the number of mosquitoes around to act as a vector for disease.

28th Feb 2010