May 18, 2013

Malaria parasite drives infected mosquitos to aggressively pursue human blood

Malaria parasite drives infected mosquitos to aggressively pursue human blood

Malaria parasite drives infected mosquitos to aggressively pursue human bloodby David Ferguson | British researchers announced Wednesday that they have established that the malaria parasite makes the smell of human beings even more irresistible to mosquitos that feed on our blood. According to a paper published in the Public Library of Science’s PLOS One journal and reported by NPR, mosquitos that carry malaria are even more powerfully drawn to the smell of human prey than their uninfected fellows.

Entomologists at the London School of Hygiene and Tropical Medicine conducted an experiment in which mosquitos were given a choice whether to fly to a clean sock or a sock that had been worn for 20 hours by an adult male human. All of the mosquitos chose the dirty sock over the clean one, but the malaria-infected bugs landed on the fabric again and again, trying to bite and draw blood.

Mosquitos track humans through our scent. Human skin gives off more than 350 odor molecules, all of which combine to form an irresistible fragrance cocktail to hungry female mosquitos, who need human blood to nourish the larvae that will hatch from their eggs. It would appear that infection with malaria, which is neither a virus nor bacteria, but a single-celled, blood borne parasite, drives the mosquitos to feed more often, thus allowing the disease a greater chance to spread via the mosquitos’ saliva.

Invasive parasites have been found to exert control over the behaviors of their hosts in several species. In ants, the fungus Ophiocordyceps unilateralis invades the brain and compels the insects to climb to the highest point they can find, at which point the fungus explodes from their head in the form of a spore-casting mushroom, killing the ant, but scattering spores over the widest possible area.

The blood infection Toxoplasmosis gondii is believed to make rats crave the smell of cat urine, increasing their chances of being killed and eaten by cats. Toxo needs to complete the next phase of its development in the bloodstream of a cat, hence its influence over the rat’s normal fear of the smell of its natural predator.

Some scientists postulate that Toxo can exert control over some human behaviors as well, making them, too, less repelled by the smell of cat urine and giving rise to the so-called “crazy cat-lady effect.” Toxo can only make the jump from cats to humans during one phase of its development, however, which can only occur during a certain during in a cat’s first year of life.

According to the World Health Organization, malaria kills around 655,000 people worldwide every year, many of them children in Africa. Health activists would presumably welcome new advances in malaria prevention since resistance to current treatments is growing in new malaria cases. The current main treatment for malaria, artemisinin, is requiring higher and higher doses to work and no new drugs or treatments appear to be in the pipeline for testing or further research.

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