If you like cats, have a cat, or are simply interested in a superb popular science piece, do read this article in The Atlantic by Kathleen McAuliffe: “How your cat is making you crazy.” It’s about new research on the disease toxoplasmosis, caused by infection by the protozoan Toxoplasma gondii (here it is):
The primary host is, sadly, kittehs, and the oocysts (tough spores containing the zygote) are passed on in cat feces, which can go on to infect other species, including humans. (This is why pregnant women aren’t supposed to handle cat litter, though the disease is limited to cats who go outside.) Here’s the life cycle, complete with an evil-looking cat (for which I apologize):
Anyway, you may know of new research suggesting that the parasite itself can manipulate rodents to make them more susceptible to cat predation. Infected rats or mice not only show less fear of cats, but are even attracted to the scent of cat urine, which normally repels them. This may be one of those fascinating cases in which a parasite takes over the behavior of its host to further its own transmission. (When a cat eats an infected rodent, it gets infected itself, an essential step in the parasite’s life cycle.)
McAuliffe, however, dwells on new findings that humans infected with toxoplamosis—and there are many of us, about 30% of the world’s population—may show subtle behavioral changes, or even drastic ones. She notes that the incidence of infected people is more than twice as high among involved in traffic accidents than among people in a non-accident control group, and she cites research showing that infected human males tend to dress more slovenly than those who are non-infected (those males also show a higher attraction to the scent of cat urine). In contrast, infected women dress more meticulously. Finally, there may be a connection between Toxoplasma infection and schizophrenia, though the data are very preliminary.
I recommend this article highly: it’s really well-written and full of intriguing information. It’s the paradigm of what a popular science piece should be, and I hope McAuliffe, whose website is here, produces more of these.