MALARIA: World Malaria Day

Mun-Keat Looi
Not many people like mosquitoes. For the ‘lucky’ ones, they are just pesky insects that surreptitiously suck your blood, leaving you with itchy bites in parts of your body you didn’t even know you had.
But their stock gets even lower in tropical countries where, as residents and Cheryl Cole know all too well, the little blighters spread a variety of unpleasant diseases, chief among them malaria.
Today is World Mosquito Day, marking the 1897 discovery that female mosquitoes transmit the malaria parasite between humans. As the charity Malaria No More state, the discovery by British doctor Ronald Ross laid the foundations for scientists across the world to better understand the role of mosquitoes in disease.
So what are the issues and what’s being done to combat them?
For some researchers, the mosquito represents an opportunity to break the cycle of transmission. Bednets are one of the cheapest and most effective ways of preventing disease transmission, simply by preventing the mosquito bite. Insecticide sprays and repellents have been used for years to great effect, though there is evidence of resistance emerging. Meanwhile, other researchers are trying different ways of trapping mosquitoes, including creating a synthetic scent they find irresistible.
More audacious is the use of genetically modified mosquitoes to disrupt natural mosquito populations. Ideas include modded mozzies resistant to the malaria parasite, and sterile mosquitoes that can mate but can’t breed to drive down their numbers (a technique that has been used against agricultural pests for over 50 years). There has already been some success and the Wellcome Trust is funding field trials on one GM mosquito created by Oxford-based company Oxitec Ltd. However, as SciDev.Net reports, harnessing the GM approach is not as simple as it seems.
Some of you may prefer that we wipe all mosquitoes off the face of the earth – a tactic that, perhaps surprisingly, has few ecological consequences according to a recent news feature in Nature. Alas, total eradication is a challenge in itself and to take such action would also rob us of the opportunity to learn more about the way mosquitoes interact with viruses, parasites and bacteria, revealing defensive tactics we ourselves might use. For example, Trust-funded research published earlier this year revealed how the mosquito immune system produces two proteins that help it to kill 80 to 90 per cent of malaria parasites.
Meanwhile, European researchers were stunned by the recent discovery of the tropical Aedes aegypti mosquito in the Netherlands. This particular mosquito species is known for spreading Yellow fever, Dengue fever and chikungunya virus.
That reminds me of an artwork in the Medicine Now gallery of Wellcome Collection. ‘Mosquito Coast’ appears from afar to be a standard world map, but closer inspection reveals that the outlines are made up of thousands of mosquitoes. It reminds you of how prevalent mosquitoes are around the world (did you know there are 3500 species?). Like them or not, they’re everywhere, making the diseases they spread that much harder to stop.
Finally, you may find this 1953 film of a mosquito dissection for malaria parasites useful for some background or just a sense of schadenfreude from seeing one being diced up….
To find out more about mosquitoes and malaria visit the Wellcome Trust’s Malaria website
http://wellcometrust.wordpress.com/2010/08/20/beware-the-bite-world-mosquito-day/