Africa: Genetically Altered Mosquitoes Could Help Fight Dengue Fever

MediaGlobal (New York)| 4 March 2010|

Last week, the US National Academy of Sciences published a study suggesting that genetically modified mosquitoes could help fight dengue fever.

According to the World Health Organization (WHO), 2.5 billion people in more than 100 countries are at risk of dengue fever. An estimated 50 to 100 million cases occur annually, resulting in 22,000 deaths, most of which are children.

Reported cases of dengue fever have steadily been on the rise since the 1960s, and reached a peek during a pandemic in 1998, with 1.2 million cases. Ashook Moloo, from the WHO Department of Control of Neglected Tropical Diseases, told MediaGlobal: “Dengue is the most rapidly spreading mosquito-borne viral disease in the world. In the last 50 years, incidence has increased 30-fold with increasing geographic expansion to new countries and, in the present decade, from urban to rural settings.”

Currently there is no specific treatment or medication for the virus, nor is there a preventative vaccine available. Rest and consumption of fluids is considered the best course of action, though some patients require blood transfusions in cases of dengue hemorrhagic fever, a complication of dengue fever.

The virus is spread by the Aedes species of mosquito, which transfer the virus after biting an infected individual. As such, other forms of prevention, such as removing standing bodies of water where mosquitoes lay eggs, is thought to be the best defense against contracting the illness.

However, many of the recommended precautions against dengue are not an option for the world’s poorest people, who are often most at risk. Installing bug screens on homes, and purchasing bug repellant or mosquito nets simply is not possible for many in developing countries where dengue is prevalent. Furthermore, chemical insecticides used to control mosquito populations are often detrimental to the environment.

In the new study released 22 February, a group of scientists bred genetically altered Aedes mosquitoes to produce females, who are the ones that bite and spread dengue, that cannot fly.

According to the study, males were altered, and then bred, and their female offspring were flightless, while the males remained unaffected. Additionally, the genetic modification will be limited only to the dengue-carrying species, as Aedes males cannot mate with other species of mosquito.

The plan would be to spread eggs containing the genetically modified males in dengue fever prone areas, and have these males mate with wild females to produce the next generation of flightless females, and thus restrict the local mosquito population and the spread of dengue in an estimated six to nine months.

In addition to this being an eco-friendly way to control the mosquito population without insecticides, the study’s head scientist Luke Alphey from Oxford University told the BBC that “another attractive feature of this method is that it’s egalitarian – all people in the treated areas are equally protected, regardless of their wealth, power or education.”

This study also brings hope that a similar approach could one day be employed to help eradicate the spread of malaria, especially since certain strains of malaria are becoming more drug resistant. However, the main setback is that malaria is carried by many different species of mosquito, rather than just one, as in the case of dengue fever.

So while this study shows great promise for an effective way to control dengue fever in a socially equal and environmentally friendly fashion, there is still a ways to go before it is put to use. Moloo said that “genetically modified mosquitoes have to prove [their] fitness in the wild population, and [their] effectiveness in suppressing natural population of the mosquito.”

In addition to getting funding to release enough eggs, and in the right areas to influence the native population, Moloo pointed out that trials of this method “need to get national, ethical, regulatory, and bio-safety approvals from competent authorities.” This all needs to happen before this tactic is used on a mass scale.