Sunday, February 25, 2007

The Return of the Puppet Masters.

We have Glenn Reynolds to thank for this link to an article about Toxoplasmosis.

Take-home: the parasite that causes this disease, which you get from changing your cat's litter box, changes your behavior in ways that spread the parasite.

(If you have trouble with that idea, consider rabies, which turns a reclusive fox into an aggressive animal whose bite transmits the disease. Or as a longtime friend, BA, once said, "If you can get close enough to a bat to touch it, that means you don't want to.")

I forwarded the Toxoplasmosis link to Patricia Romans, of the University of Toronto Zoology Department.

Dr. Pat replies,

Toxoplasma gondi is an apicomplexan parasite in the same phylum as Plasmodium (malaria). Toxo is a very good model for some things one might wish to study in malaria intracellular stages.

Malaria parasites are now well documented to manipulate the behaviours of both their human and mosquito hosts: gametocytes (the human stage infectious to mosquitoes) make their human hosts more attractive to female mosquitoes seeking a blood meal, oocysts (an asexual stage in the mosquito not transmissible to humans - they're on the basal side of the midgut) make their mosquito hosts lie low, not fly a lot or seek blood meals avidly, and mature sporozoites (mosquito stages infectious to humans in the salivary glands) make their mosquito hosts take a lot of partial blood meals in quick succession. A lot of this work comes from Jacob Koella and coauthors. I teach my parasitology students these examples, but there are lots of examples from other host/parasite associations too.

For further reading, she suggests this article and this one by Koella, adding,

The study showing gametocyte-enhanced attractiveness of humans to mosquitoes was particularly nicely controlled. The second reference is a review which will get you to all the earlier work on manipulation of mosquito behaviour. [...] There should be no problem with the PLoS Biol article but the other may not be available unless you belong to some institution that has an e-subscription to the journal. You might try getting it yourself by going to, using Koella JC, malaria as the search terms and then clicking on the article you'd like to read. Articles available free will have some kind of coloured journal logo.


Blogger nan said...

That's truly amazing info. I clean my cats' boxes a couple of times a day, at least. Maybe toxoplasmosis causes the human keeper of the cat to become very diligent in caring for their felines???

11:54 PM  

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