The hottest debate on TH!NK3 so far surrounded the use of the world’s most controversial pesticide: DDT. In itself, that discussion could form the basis for a book (who knows, I may write one after TH!NK3 is over). One of the minimal points of concensus that were to be found was that alternatives to DDT are needed. The sooner the better.
Well, here it comes. And I will also tell you why it hasn’t been developed to the level where full-scale production and implementation has become reality.
Eleven years ago, I was setting up a laboratory in Nairobi, Kenya. At the International Centre of Insect Physiology and Ecology. Down the corridor, Dr. Maniania, a sturdy man from Congo DR, was experimenting with fungi that could be used to kill tsetse flies. When one day a student from the University of Nairobi asked me to supervise a small project, I sent her over to Maniania to get some fungus. ‘Try this on malaria mosquitoes to see if it kills them’, I suggested. Off she went. A week later she returned with some transparent test tubes with moldy mosquitoes in them. I couldn’t believe my eyes. I was looking at the first successful killing of adult African malaria mosquitoes with a biological control agent – a fungus called Metarhizium anisopliae.
Soon afterwards a student from the Netherlands, Ernst-Jan Scholte, joined me in Kenya, and for six months he worked hard to bring out the first results with fungus. Not only did he infect malaria mosquitoes, he also killed Culex mosquitoes with it that transmit elephantiasis, a grossly debilitating disease. With his long curly hair and a beard, Ernst-Jan was the perfect personification of a hippie looking for green ways to control malaria. His resemblance to Jesus was so striking that some Kenyans thought he could walk across Lake Victoria!
Ernst-Jan went on with his studies in southern Tanzania, where he teamed up with a bright young MSc student called Kija Ng’habi [see picture of the two]. Together they staged the first open field trial of fungus in a small rural village called Lupiro. By applying the fungus (in sunflower oil) to black pieces of cotton cloth (3 sq m each) that were fitted against the roofs inside local houses, they managed to infect almost a quarter of the mosquitoes entering the house [see mosquitoes sitting on fungus-treated cloth in image]. That fantastic result was published in the top journal Science in 2005. The Tanzanians were over the moon with this accomplishment, and Kija rose to great heights on national TV and radio. It was well deserved.
'Shoot it down'
But although the world was presented with a new and green method to control malaria mosquitoes the critics lined up to spoil the euphoria.
Many scientists working in the field of malaria will evaluate someone else’s success with the words ‘Interesting, but…’. What follows is a string of arguments why the new invention won’t work, and why theirs is the thing to go for. A renowned scientist (that resides on many committees that decide on funding and now works for WHO) even went to the extent of talking about ‘fatal flaws’ in a commentary published in Science. These critics did a perfect job in line with Malaria: Can science cripple development? They argued in favour of their own preferred line of attack at the expense of other solutions under development.
Now it is 2010, and eleven years have passed since that first discovery in Nairobi. We know now that when a mosquito becomes infected with fungus that she will not perish immediately. And that is a good thing, as it prevents the likelihood of resistance to fungus developing. We also know that fungi kill mosquitoes that have become resistant to insecticides used on bednets. Dutch PhD student Marit Farenhorst, when working in South Africa, produced fantastic results that again reached the top charts in the published literature. She later demonstrated the effects of fungus against insecticide-resistant mosquitoes in Benin.
But this fungus cannot be patented. Bummer. Although it is being produced on a commercial scale in three places in Africa (Dakar, Nairobi, Durban), there is still no formulation that can be used on a grand scale in malaria control programmes.
Here is a green method to kill malaria mosquitoes. All it requires is investment to scale up production and develop suitable formulations and application methodology. But it is unlikely fungi will ever replace DDT. Metarhizium was originally developed to control outbreaks of the desert locust and to replace the toxic chemical malathion. Millions were poured into developing this biopesticide. Its use has never come to flourish.
So, when talking about alternatives for DDT, fungi certainly are promising. But as long as scientists within the field of malaria are negating its potential, we all shoot ourselves in the foot. And if industry is not turning it into a product we have produced nice articles in scientific journals, nothing more.
It is high time that we don’t all fight for the single egg to put into our own favourite basket. We should fight to get many eggs, and place them in every basket.