Comments on: Parasites as Neuropharmacologists

By: David Lindeman

David Lindeman — Tue, 28 Oct 2008 20:43:50 +0000

I’m working on a theory I call “Para Cata Fungo Genesis” It is similar to Symbiogenesis. Your book and posts have given me some great info .Thanks

By: Darby

Darby — Fri, 20 Apr 2007 02:14:07 +0000

Where did you run across the claim that most humans harbor Toxoplasma? As I understand it, during the period when pregnant women were routinely checked for Toxoplasma antibodies, positive results were not that common, even for lifelong cat owners.

By: Daniel Kim

Daniel Kim — Sun, 15 Apr 2007 15:20:48 +0000

This fascinating story gets better and better all the time.

Recently, there was a post on this subject at Neatorama:

http://www.neatorama.com/2007/04/04/parasite-can-alter-hosts-fear

I felt the need to reply to one of the comments there with a speculation on the evolution of such specialized brain localization. My guesstimate was that the parasites may target themselves to different tissue types by binding to tissue-specific markers.

Some years ago (six? seven?), an experiment was done in which filamentous bacteriophage were used to create a library of random peptide motifs that were “displayed” on their coat protesin. Each virion would express a different motif. This “phage display library” was then injected into the bloodstream of a mouse. After some incubation, different organs were taken, and bacteriophage were recovered from them. The bacteriophage population found in a particular organ was presumed to be enriched for phage that display peptides that confer tissue-specific localization.

After successive rounds of clonal isolation, propagation, selection by injection into more mice and harvesting; clonal isolates were found that could be targetted to specific tissues. The authors proposed that this type of targeting might be used to deliver drugs to specific organs or tissues; or even deliver drugs to tumors for chemotherapy.

So I wonder if there is any evidence of this kind of tissue-targeting in T. gondii. Phage display library enrichment is a laboratory-based evolutionary process, and is illustrative of the way that a parasite might evolve the kind of characteristics we are seeing now in Toxoplasma.

By: kenneth

kenneth — Thu, 12 Apr 2007 02:52:43 +0000

Just finished P-Rex. What a read. I hadn’t the remotest notion. Thanks.

I set down the book and found your blog. Looking forward to more scientific surprises…

By: pat

pat — Thu, 05 Apr 2007 03:58:41 +0000

Toxoplasma gondii is an incredible example of evolution in action. I’d be interested to know the distribution of the infection in the US by state. We read that Korea has a low infection rate and Brazil a high one. Do US States have a similar variance?

By: Joshua

Joshua — Thu, 05 Apr 2007 02:39:25 +0000

Actually, Carl, I suppose that in itself goes a long way to explaining the success of Toxoplasma.

It would be interesting to know when that ability to survive in hosts other than its two first choices (rats and cats) developed and whether that correlates with this evolutionary sweet spot indicated by this research.

By: raindogzilla

raindogzilla — Wed, 04 Apr 2007 15:21:04 +0000

Maybe Genesis is actually the story of Adam and Eve Toxoplasma and the YECs are just a couple thousand years off in their calculations!

By: Brian Baker

Brian Baker — Wed, 04 Apr 2007 06:27:06 +0000

Edit: “perhaps it have evolved”

By: Ross

Ross — Wed, 04 Apr 2007 00:23:04 +0000

>a common set of parental strains that lived 10,000 years ago

Would this time relate well to the time that cats were first domesticed, following the availability of bulk grain from agriculture? Domestication brings many unrelated cats together for social contact and would allow greater spread of toxoplasma.

By: Carl Zimmer

Carl Zimmer — Tue, 03 Apr 2007 18:51:09 +0000

Joshua–I should have pointed out that Toxoplasma can infect any mammal or bird. Awesomely versatile. So rats may not be the secret to their success.