Scientists aim to mislead malaria mosquitoes with odours

Jun 29 2005

An international team of scientists will in the coming five years set up a research project on developing diversions to mislead malaria mosquitoes with odours.

With these the number of cases of malaria in tropical Africa may be reduced strongly. Scientists at Wageningen University will be working with colleagues in the USA, Tanzania and Gambia on a project led by Vanderbilt researchers that has received $8.5 million dollars (approximately 7 million Euro) from the U.S. Foundation for the National Institutes of Health and the Bill and Melinda Gates Foundation as part of their Grand Challenges in Global Health Initiative.

In the team are scientists from Vanderbilt University, Yale University and Wageningen University who will be co-operating with researchers from the Ifakara Health Research and Development Centre in Tanzania and the Medical Research Council Laboratories in Gambia (Africa). They aim at reducing the population of malaria transferring mosquitoes by setting up odour traps and effective repellents that keep malaria mosquitoes away from potential human hosts. In this fashion, they hope that the risk of malaria transfer may be reduced substantially.

To find a proper host (the human being) female malaria mosquitoes head for the odours they intercept with their antennas. After they recognise the host’s odour, they suck up blood that hey need for egg production. As the mosquito is drawing blood, parasites from the mosquito enter the human body. A small percentage of malaria mosquitoes are infected by the Plasmodium parasite. These parasites (Plasmodium spp.) are responsible for the malaria disease. When an infected person, after an incubation period of ten to fourteen days, is bitten again by a mosquito, the malaria parasite is transmitted to the mosquito and so is spread more widely throughout the mosquito population. The change for other people of being infected will increase. The number of malaria cases is world-wide between 300 and 660 million per year and is the most important life-threatening disease in the world, causing more than a million fatal victims pro year.

The malaria mosquito Anophels gambiae heads for a complex of odours to find a host. The research team of Vanderbuilt University (Nashville, Tennessee) and Yale University (New Haven, Connecticut) in the USA will develop odour material for which the mosquito antennas are very sensitive. This team will identify and test either attractive or repellent odour materials or materials causing confusion. After that the Wageningen University team will look at the effect of the interesting odour materials from the American research on mosquito behaviour. The materials (substances) giving the strongest reaction (attracting, repelling or causing confusion) will then be tested in a simulated natural situation in Ifakara, Tanzania. The ideal blend of odours will find its way to African villages for full-scale, practical tests as part of the project. The villages are located in the Gambia and Tanzania and are situated in different geographical extremes with different mosquito populations. The results of the research project should therefore be applicable for much of tropical Africa. If the experiments are successful African households will have an added degree of protection provided by strong new repellents or odorants that confuse the mosquito’s sense of smell, causing less mosquito biting, while outside the villages insect traps are baited with attractive odorants that the insects can’t ignore. The ultimate goal is to reduce malaria transmission by the use of odorant devices.

The eventual products can be deployed against other pathogenic mosquitoes, such as the mosquito Aedes aegypti spreading dengue fever and against Culex pipiens, carrier of the West-Nile virus.

Earlier this month news spread about a new biological approach for fighting malaria mosquitoes developed by the entomology team of Wageningen University. Its research identified a fungus that seriously weakens or kills the mosquitoes before they can infect people with malaria parasites. This illustrates the fact that the Wageningen team is working on several methods of fighting the malaria mosquito that could be combined to form an integrated strategy for fighting this deadly disease.