How Scientists Are Using Genetically Modified Mosquitos to Combat Disease

Jacobina is a small farming town in the eastern Brazilian state of Bahia. Like in many other places in Brazil, Jacobina is plagued by dengue fever The most serious form of the disease, known as dengue hemorrhagic fever, can cause shock, comas and death. The disease is primarily carried by the Aedies aegypti species of mosquito and is one of the leading causes of illness and death in Brazil.

The people of Jacobina had tried out all sorts of different strategies to combat the disease-carrying mosquitos with little success. Methods like air fumigation and putting larvicides in the water were ineffective because the mosquitos tend to live and breed inside homes, and are able to build up a resistance to the insecticides.

Mosquito nets put over beds had little impact because the mosquitos that carry the disease only bite during the day, and public education campaigns urging citizens to wear long sleeves and use repellent mostly fell upon deaf ears.

The city of Jacobina- click to enlarge. (Photo: Carlos Augusto)

So Aldo Malavasi, president of Moscamed, decided to try out a bold, mostly untested strategy. He and his team worked with mosquitos genetically modified with a lethal gene (the mosquitos are kept alive in the lab using the antibiotic tetracycline). This method for genetically modifying mosquitos originated with Oxitec, a company which describes itself as an “innovative insect controller”.

The modified mosquito, known as the OX513-A, is the first ever genetically modified insect to be released into the wild- they were initially tested in 2010 in the Cayman Islands and Malaysia, but only in small numbers.

Once Moscamed’s collection of genetically modified mosquitos reached larval state, Malavasi and his team extracted all the males (who don’t bite) and destroyed the females.

Twice a week, Moscamed workers hop in trucks and drive around releasing the genetically-altered males, who then mate with females, passing on the lethal gene which kills the offspring since they have no access to the antibiotic.

A worker releasing genetically modified mosquitos (Photo: Vincent Bevins/L.A. Times)

There have been some concerns raised though. Among these is the worry that a decline in Aedies mosquitos will simply lead to an increase in the population of Asian tiger mosquitos, which also live in the area. Malavasi points out, however, that tiger mosquitos are much less efficient in terms of spreading dengue fever.

Some critics of genetic modification also raise concerns that a few female mosquitos will inevitably end up getting released with the males, and worry about the consequences of one of them biting a human. Malavasi also dismisses this worry, saying that it’s highly unlikely that the female mosquitos would come into contact with the antibiotic tetracycline in just the right doses for them to survive after release.

Malavasi also stresses that field tests in isolated towns like Jacobina are what give us the answers to many of our questions and concerns, adding,

“We need to provide alternatives because the system we have now in Brazil doesn’t work.”

Alvo Malavasi (left) examines a sample of mosquitos with a colleague
Aldo Malavasi (left) examines a sample of mosquitos with a colleague

The people of Jacobina, tormented by dengue fever for years, are all for the plan, and Moscamed does a good job of remaining transparent. They hold regular public meetings with local health officials to answer questions and have passed out literature about the project to the people of Jacobina.

Moscamed has reported a 90% decrease in the population of the Aedies mosquito thus far.

Read more from the Global Post here.

Feature photo courtesy of CORBIS.

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