Can flightless mosquitoes be used to control dengue?

26 Feb 2010

Paul Chinnock

Source: PNAS (see original article)
Source: BBC (see original article)

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The Aedes aegypti mosquito can transmit dengue and other serious infections. [Credit: Muhammad Mahdi Karim.]

The sterile insect technique (SIT) is successfully used in agricultural for the control of several insect pests, as an alternative to the use of insecticides. However, there are no SIT programmes in operation to control insects that transmit human diseases. Attempts to control mosquitoes using SIT have been unable to overcome the many technical problems that have been encountered. Now, however, a team of UK and US scientists have reported success (1) in breeding genetically-altered male mosquitoes that are able to mate with wild females, but in the process pass on a “lethal” gene.

The researchers have shown that females of the next generation are unable to fly because normal wing growth does not take place. The next step would be to distribute many thousands of eggs that would hatch out the genetically modified males, leading on to the creation of a new generation of flightless, and consequently doomed, females.

The mosquito used in the research was Aedes aegypti, vector of dengue fever, yellow fever and chikungunya. There will be particular interest in the possibilities this research opens for dengue control; there are now over 50 million cases of this disease every year and no vaccine or specific treatment is yet available. It is to be hoped, however, that the technique could be developed further for use against diseases transmitted by other mosquito species, including malaria.

The researchers chose to develop genetically altered males for release in the environment because it is female mosquitoes that bite. Eggs would be used for release because they are easier to distribute than adults and it should be possible to create situations where the males carrying the lethal gene outnumber the resident male population. Nevertheless, as the authors of the study point out, “Further studies are needed to assess the mating competitiveness of males of specific strains, and their operational effectiveness in suppressing wild mosquito populations”.

Dr Hilary Ranson of the Liverpool School of Hygiene and Tropical Medicine told the BBC that the research was a significant advance: “It will be logistically challenging to make and release enough of the male mosquitoes and it’s not going to be cheap. But it can be done with the right resources. She said dengue fever was an ideal disease to tackle in this way because it is spread by only a couple of species of mosquito.

Dr Ranson stressed, however, that malaria would be harder to beat because of the variety of mosquitoes carrying the disease.

Reference

1. Fu G, Lees RS, Nimmo D, Aw D, Jin L, Gray P, Berendonk TU, White-Cooper H, Scaife S, Kim Phuc H, Marinotti O, Jasinskiene N, James AA, Alphey L (2010). Female-specific flightless phenotype for mosquito control. Proc Natl Acad Sci USA; 2010 Feb 22. [Epub ahead of print]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/20176967