Science - August 28, 2014

‘If this works, everyone will want to come on board’

Text:
Albert Sikkema

Professor Willem Takken wants to wipe out malaria in Africa without using chemical pesticides. To this end his research group has developed mosquito traps containing odours that attract the malaria mosquito. The big test case is now under way. On Rusinga island in Lake Victoria, all 4500 households are being issued with a mosquito trap with the aim of eradicating malaria on the island.

Malaria is the biggest infectious disease in Africa. Every year, millions of Africans being infected with the Plasmodium parasite which is transmitted by malaria mosquitoes. Half a million Africans, most of them young children, do not survive the infection. As a medical entomologist, Willem Takken has been studying options for combatting malaria for years. The time has come for his research to pay off. Takken’s research group is half way through a project aiming at wiping out the disease on an island in the middle of Africa. 

The place in question is the Kenyan island of Rusinga in Lake Victoria, where all 4500 households are being equipped with a malaria trap. Every week technicians from the project are installing 50 traps containing a mix of odours partly developed in Wageningen, which are highly attractive to malaria mosquitoes. Thanks to the traps, the mosquitoes no longer reach the residents’ bedrooms. Because the odour-baited traps require a little electricity, the project is also placing small solar panels on the roofs of the Rusinga houses, providing many of the island dwellers with electricity for the first time. 

The project is very popular with the local population, says postdoc Alexandra Hiscox of Entomology, who coordinates the project in Kenya. ‘The residents benefit directly from the project because, quite apart from the expected drop in malaria, they no longer have to buy kerosene for their lamps and they can recharge their mobile phones whenever they want to.’

The negligible number of theft cases also speaks volumes, says Hiscox. ‘We have now installed 2500 mosquito traps and solar panels, and to date no more than 10 solar panels have been stolen. That is a tiny number.’ Takken and Hiscox consult a residents’ committee four times a year. The committee is made up of two chiefs from the island, and representatives of the church, fishing villages, women’s organizations and international NGOs. 

One chance 

The entire operation, including material and installation, only costs 150 euros per household. The solar panels cost only 25 euros each, because they are supplied by a Dutch company in Kenya which imports substandard solar panels and refashions them into smaller models. The total costs of the project amount to 3.5 million euros, financed by the COmON foundation through the Wageningen University Fund. The costs are not just for the installation of the malaria traps, says Takken, but also for research. A multidisciplinary team of researchers is monitoring the success of the project. The researchers monitor the mosquito density on the island and check the population for malaria three times a year. Takken does not have any research results yet; these will only come in next year when the project is over. He does not want to draw conclusions prematurely because this is a crucial test case for the battle against malaria. ‘We only get one chance. If the results are disappointing, it will never happen again. If it goes well, everyone will want to come on board and use the famous odour mix. That is why we are going to analyse the research data very carefully.’

What he can say already is that one quarter of the 2500 island dwellers currently have malaria parasites in their blood. Ten years ago, that figure was 50 percent. This drop has nothing to do with the project, but came about because the Kenyan government distributed free mos-quito nets in an effort to reduce the incidence of malaria. That has been a big success throughout Africa, says Takken, but it does not completely solve the problem. In fact, Takken has evidence that mosquitoes adapt to the use of bed nets. People are now being bitten out of doors and during daylight hours. This is why the fall in numbers of malaria patients levelled out in recent years, and the mosquito traps are still badly needed. 

Malaria 

Earlier research has established that odour-baited traps catch 32 percent of the mosquitoes present around the house. Using models, you calculate on this basis how fast the malaria rate will go down and how long it will take before malaria mosquitoes are eradicated. But whether events will unfold according to this model on Rusinga, Takken cannot yet say. He does not think the mosquitoes can adapt so as to avoid the traps, because they need their odour recognition to find food. This may make the odours a sustainable alternative to insecticides for combatting malaria mosquitoes.  

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Odour baits, the basis of the project 

The project aiming at ridding Rusinga island of malaria started in August 2012. If all goes to plan, the last malaria trap will be installed in February 2015. The basis of the project is a powerful bait created from a mix of odours. Over recent years, the Entomology group tested hundred of odours on the antennae of mosquitoes, which detect the smells. What do they respond to? Five key odours emerged which are part of the human odour profile. According to Takken, tests reveal that this odour mix is just as attractive to the malaria mosquito as the smell of a human being. Subsequently, the researchers had to create the ideal mix of these odours in the right concentration. Entomology has applied for a patent on this successful cocktail of odours. 

The odour mix catches the two main malaria-carrying mosquito species: Anopheles gambiae and Anopheles funestus. These species are found all over sub-Saharan Africa. If the project succeeds, it will be of interest to other malaria-infested countries such as Malawi, Burkina Faso and Cameroon. 

So why did Takken end up working on Rusinga? It provided a research area that was representative of other parts of Africa but not too big (on account of the costs). Also, malaria studies had already been conducted on this island and the two main malaria mosquitoes are found there. A further reason is that the main research partner in this project – the International Centre of Insect Physiology and Ecology – is based in Kenya. 





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