Sunday, June 19, 2011

Malaria Mozzies and their Foot Fetish

[This was written by Fran Siebrits and published online by Wild Magazine http://www.wildcard.co.za/, 2011]


There are some strange fetishes out there, but this one has to take the cake … Malaria mosquitoes are attracted to human toes.

It is true that mosquitoes “sniff” us out by following the carbon dioxide trail we exhale. The latest research now shows that until a certain distance, some mozzies stop following our breath and head for our feet.

Within the last few metres of acquiring their target, the malaria mosquito alters its course, heading instead to the preferred foot odours.

From tens of metres away, the African malaria mosquito (Anopheles gambiae) can detect carbon dioxide. As this forms part of our exhaled air, female mosquitoes are able to pin-point their next blood-meal. At a certain distance away, they no longer aim for the mouth but for the feet, their preferred biting place.

Previous research has shown that there are different bacteria living on the human foot. Each one produces a particular odour. When certain bacterial foot odours are blended together, they become attractive to malaria mosquitoes.

Ten different blends of bacterial odours have been discovered, and half of these are able to block the response a mosquito has to carbon dioxide. When a malaria mosquito can no longer detect carbon dioxide, it orientates itself to the foot odours instead.

Malaria mosquitoes identify carbon dioxide and bacterial foot odours by olfactory neurons near their mouthparts. From these many olfactory neurons, only one is capable of detecting carbon dioxide. By blocking the signal of carbon dioxide, foot odours disrupt the host-seeking behaviour of malaria mosquitoes. Additionally, these odours stimulate other olfactory neurons, altering the mozzies course of action once in a certain range.

Unfortunately, this doesn’t mean that if you sleep with your feet under the duvet you won’t be bitten. As soon as the foot odours are no longer interfering with the ability to detect carbon dioxide, mozzies will head straight for their original target … the mouth. It’s blood they want and it’s blood they have to get!

Source: Wageningen University and Research Centre (2011, May 6). Malaria mosquitoes accurately find their way to smelly feet. ScienceDaily.


Viewed online [http://www.sciencedaily.com¬/releases/2011/05/110506073756.htm]

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