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Friday, December 15th 2006

Mind Controlling Parasites

I heard about Toxoplasma gondii way back in high school, but was reminded of it last year in Microbiology. This little fella, which completes the maturating part of its life cycle only with felines, appears to cause infected rats to lose their fear of the smell of felines…thus increasing the rat’s chances of getting eaten by a cat and thus allowing T. gondii to infect the cat where it can complete its life cycle.

In other vertebrate T. Gondii is associated with movement disorders. In humans there’s evidence infection increases your risk for schizophrenia.

Now there is a cool write up and video of Spinochordodes tellinii causing infected crickets (and other insects) to committ suicide in water, so that it can escape (the adult form of the parasite only lives in water.

Ah, A Refreshing Swim! *Gurgle*

This is a report on a study from France,

Once in the water the mature hairworms – which are three to four times longer that their hosts when extended – emerge and swim away to find a mate, leaving their host dead or dying in the water. David Biron, one of the study team at IRD in Montpellier, France, notes that other parasites can also manipulate their hosts’ behaviour: “’Enslaver’ fungi make their insect hosts die perched in a position that favours the dispersal of spores by the wind, for example.”

But the “mechanisms underlying this intriguing parasitic strategy remain poorly understood, generally”, he says.

Now Biron and his colleagues have shown that the worm brainwashes the grasshopper by producing proteins which directly and indirectly affect the grasshopper’s central nervous system.

Biron and colleagues found that the adult worms – those ready to prime their hosts for a watery death – altered the central nervous system function of their hapless hosts by producing certain molecules mimicking the grasshoppers’ own proteins.

Apparently they haven’t identified the function of these alien proteins or how they affect behavior in the grasshopper, but at least it is a step.

Here’s a review of parasitic manipulation in Behavioral Processes.