This is in line with the article on Toxoplasmosis, a parasite known to make rats fear cats less, and its affects on the human nervous system. It is intriguing to consider at the very least.
Two medical articles: Toxoplasma gondii and Schizophrenia and Effects of Toxoplasma on Human Behavior respectively.
all toxo, all the time
http://toxoplasmaparasite.blogspot.com/
and i still like the trade article, How Your Cat is Making You Crazy
This is interesting, I wonder if there's anything to it: International variation in IQ – the role of parasites (paper) by Christopher Hassall of U. Carleton.
It strikes me as the sort of thing that could be as big an issue as lead in the environment. Raise the sanity waterline: improve health!