Funny thing is, the Toxo parasite has also infected a certain percentage of human brains (and hides pretty well). Infection varies by country - France and Germany, for example, have a high rate of infection while South Korea has a very low rate of infection.
What is to stop these parasites from changing human brains like they do to rats? Do they perhaps make people more prone to loving the primary host, the cat? Do they turn people into crazy cat ladies? If one parasite can do this, what other parasites are in our bodies altering our behavior? And finally, if they vary by country, are they to some extent influential on the culture of a people?