Wetenschap - 1 maart 2011

Floating fungi tackle Malaria at source

Tullu Bukhari has developed a biological control agent that kills mosquito larvae in water puddles in Africa. This strategy will tackle the cause of Malaria at the source.

Bukhari, a PhD student at the Laboratory of Entomology in Wageningen, is carrying out research to determine the potential of two fungi, Metarhizium anisopliae and Beauveria bassiana, for the control of Malaria mosquito larvae. Both fungi have the ability to kill Malaria mosquitoes and have also been tested recently against adult Malaria mosquitoes in African homes.
Bukhari wants to develop a substance for biological control of mosquitoes that is efficient under field conditions. Mosquito larvae breed in a variety of aquatic habitats. However, water decreases the workings of the fungal spores. Therefore she searched for carriers to protect the fungal spores in water. The synthetic oil ShellSol T does exactly that. Moreover, the floating spores in the oil formulation are able to infect mosquito larvae and the oil also helps to disperse spores over the water surface, she found out in her lab in Wageningen.
She then experimented with the new formulation on a test site in Kenya, where Malaria is transmitted by the Anopheles gambiae mosquito. A small-scale test in artificial ponds showed that the number of mosquito pupae was 40 to 50 percent less in ponds with the formulated spores than in ponds without. Given the fact that about 30 percent of the larvae died of natural causes, Bukhari estimates that only 20 percent of the mosquito larvae can survive in a pond with formulated spores. In addition, mosquito larvae that manage to survive to the adult stage may still have the fungal infection in them. This has been found out previously in the laboratory. The infected adults produce less eggs and bite less.
Bukhari stresses that the required dose of ShellSol oil is not harmful to the aquatic environment and has no toxic effect on any other organism in the water. Moreover, the quantity of oil will not build up over time at the sites despite repeated applications because the oil evaporates within two or three days. She now wants to conduct field tests on a larger scale to find out whether the workings of the oil can also lead to less instances of Malaria.
The next major step is to mass-produce fungal spores cost-effectively.  Bukhari used fungal spores produced in a fermentation reactor of the Bioprocess Engineering Group of Wageningen University. Fungal spores are not yet commercially available for mosquito control. Bukhari hopes that mass production systems can be initiated in Africa, where the fungi are most needed.

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