In the small neighborhood of Itabaraba, Brazil, trucks drive around with loudspeakers piping out the tune, “Aedes aegypti, Aedes aegypti, let him into your house. He fights dengue and won’t bite anyone. He’s the good mosquito.” The trucks carry thousands of genetically modified “mutant” mosquitoes that Brazilian scientists are releasing into the wild. (Presumably, the jingle is more catchy in Portuguese.) Bred by the British firm, Oxford Insect Technologies (Oxitec), the bugs are part of an effort to eradicate dengue fever in the Bahia state of Brazil.
Dengue fever is one of the fastest growing tropical diseases in the world. Since the 1950s, the disease has grown from a few cases a year in isolated tropical regions to an estimated 100 million annually in over 100 countries, including the United States. In 2009, the first case of dengue fever in Florida in 73 years was reported and scientists now believe the disease is endemic to the state. It is particularly threatening to developing countries in tropical regions and is made worse by a lack of awareness about the disease. Experts estimate that there are approximately 37 million cases of dengue in India alone, and claim that the Indian government is not doing enough to combat the disease.
Dengue fever is transmitted by a certain breed of mosquito, the Aedes aegypti, which is indigenous to West Africa but has spread to other continents via human activity. As the mosquito has spread, the four closely-related viruses that cause dengue fever have spread with it. Most cases of dengue result in a high fever and severe, flu-like symptoms. Often times, the symptoms are mistaken for something else and are not even reported. However, if left untreated, the disease can cause agonizing pain in the joints and bones and can progress into hemorrhagic fever, shock and even death.
Because there is no vaccine or prophylactic treatment for dengue fever, the only way to combat the disease is to eradicate the mosquitoes that spread it. That’s where Oxitec’s genetically modified insects come in. The mosquitoes, which go by the ominous moniker OX513A, are bred in a lab. The males—which are harmless to human—are implanted with genes that result in their offspring dying off before they reach maturity. They are then released into the wild to breed with native females, theoretically resulting in a dramatic population decrease.
While Oxitec’s genetic modification technology is groundbreaking, this isn’t the first time that sterilization has been used to control insect populations. In the 1950s, scientists sterilized fruit flies using radiation in order to eradicate North American Screwworm. A similar technique can be used, for example, on the Anopheles gambiae species of mosquito which is the main transmitter of malaria in Africa. This approach, Oxitec argues, is better than the use of insecticides because it only targets the single species of insect. Insecticides also have the additional drawback of breeding resistance to chemicals.
While the mosquitoes seem to be working in Brazil, Oxitex is having trouble expanding its operation to other parts of the world. A recent proposal to bring Oxitec’s mosquitoes to Key West Florida drew opposition from local residents. The Florida Keys Mosquito Control Unit spends about $1 million annually, mostly on insecticides which are sprayed from trucks or helicopters. In addition to the obvious environmental impacts of this approach, it is not effective at killing Aedes aegypti which tend to live near or beneath people’s houses. Still, residents are concerned about what they call the “Jurassic Park Effect”—the unknown risks associated with releasing genetically modified insects into the wild. An organization called Genewatch points out that more of Oxitec’s insects survive into adulthood than the company claims publicly. Genewatch is also skeptical of Oxitec’s plans to get FDA approval, and expand the use of its technology to combat crop pests. In the meantime, policymakers must weigh the known risks of dengue fever and the use of insecticides, with the risk of an unknown “Jurassic Park Effect.”