by Eddy Mateescu
This urgent call, borrowed from movies about submarine warfare, applies to this non-microbial posting that is intended as an appetizer for the fascinating subject of parasite modification of host behavior. Elio promises to follow up on this subject.
In the most general sense, all living organisms must be able to detect specific, essential aspects of their environment and to react appropriately. Therefore, any component involved in the detection-decision process (from the uptake/sensory machinery and its output to the regulation/decision making system) is susceptible to manipulation by a parasite for its own advantage.
An interesting non-microbial example is that of the parasitic Nematomorph worms which brainwash grasshoppers and crickets to leave their forest habitat and take a fatal plunge into water so that the worms can emerge and mate (Movie).
A proteomic study has shown that during the manipulation phase (before the plunge into water), the parasite produces host-mimetic proteins (called Wnt) which act on the host central nervous system to cause the behavior modification (either directly or indirectly through host genome response.) During this same period, a suite of other proteins in the head of the host (for example, proteins involved in visual processing, neurogenesis and neurotransmitter activity) also increased in concentration. Remarkably, a high percentage of the worms are also able to escape from the predators (frogs and fish), which ingest their insect hosts before the worms have emerged.
This makes me wonder if it's really me wanting to swim when I go to the beach – or is it some bug living inside me?
Eddy is a physicist doing a postdoc at the Center for Theoretical Biological Physics, University of California, San Diego
Isn't that what Bush said about invading Iraq? Hmm...
My favorite is manipulation of infected rats to make them curious about cats (the next host):
Berdoy M, Webster JP, Macdonald DW. (2000) Fatal attraction in rats infected with toxoplasma gondii. Proc R Soc Lond B 267: 1591-1594.
Elio adds: You're right on all counts. We'll get to the Toxoplasma and rats story, the poster child of "parasitic manipulations."
Posted by: Ford | June 12, 2007 at 02:40 PM