Survival of the Tiniest

How the devious malarial parasite makes its host mosquito attracted to human sweat

Malaria’s route to humans is simple and straight. Plasmodium, a parasite, gets into an Anopheles mosquito and turns it into a vector. When the mosquito bites a person, the parasite enters the victim’s blood stream, multiplies in the liver and then infects red blood cells. Malaria is still one of the biggest killers in the world. World Health Organization figures for 2010 put the number of people infected at over 200 million. Lives claimed were over 650,000. While there have been treatment and prevention strategies for the disease, the parasite has been too cunning for an effective vaccine to be developed.

Recently, scientists got a fresh insight into how the parasite works its way into the human body even when it is still inside the mosquito. Science News magazine reports on a study led by the Netherlands based Wageningen University and Research Center which showed how Plasmodium points mosquitoes to the direction of humans.

The scientists made a volunteer wear nylon stockings for 20 hours so that sweat would stick to it. They then ‘put the odour-laced fabric in a cage with two groups of Anopheles gambiae, mosquitoes that transmit the malaria parasite to people. One group was infected with Plasmodium falciparum; the other wasn’t.’

They found that for every one uninfected mosquito that went towards the stocking, there were three infected ones that did the same. The natural inference was that the parasite was making the mosquitoes attracted to human sweat.

The article quotes one scientist saying that this was not a deep study because only one stocking and 176 mosquitoes were used. The researchers also don’t know how the parasite manipulates mosquitoes’ sense of smell. And it’s unclear which component of human odour is most attractive to mosquitoes.

The study was first published in PLOS One journal. But, even at such a basic level, it reaffirms the clever ways in which this parasite manipulates its environment to survive. What is even more intriguing is that it exercises such influence despite being only a single-celled organism, according to a scientist quoted by Science News.

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