If the species name Toxoplasma gondii (T. gondii) sounds familiar it is probably because you know someone who is pregnant that is no longer allowed to clean their cats litter boxes. This parasite is being targeted for a public knowledge campaign by the CDC and is known to cause severe illness later in life for fetuses of newly infected pregnant women and persons with compromised immune systems.

So how does this relate to Eleanor Abernathy? Toxoplasmosis, the disease caused by T. gondii, causes flu-like symptoms in healthy people and after initial symptoms remains dormant in the infected person forever. Dr. Flegr’s research papers suggest a link between the inactive parasite and changes in behavior. Since there are ethical issues with changing behavior in humans through infection, studies have been done on rats as test subjects instead. At Stanford University corroborating research by Dr. Robert Sapolsky’s lab has shown that rat behavior sometimes changes after a T. gondii infection. Post infection changes in the brain can cause rats to be attracted to cats instead of running for their lives. Dr. Flegr believes that this risk taking behavior and change in fear response may also be happening in humans and that behavior changes continue with duration of infection. So if Aunt Edna was exposed after adopting cat #8 and she lived another 40 years she would have increasing behavior changes with age, in essence becoming “crazier” or more different than her original personality. Maybe this also explains the abundance of cat memes…

Caveats of this argument: the effects of T. gondii are not limited to the fairer sex. Men are affected as well (they have testosterone level increases among other changes) so crazy cat men are out there! The research being done on human personality is preliminary and suggestive but there is plenty of controversy in the scientific community over the relationship of personality changes and T. gondii infection. However, if flatworms and fungus can change insect behavior then there is precedence for parasites causing behavior modification in higher organisms as well. If you are interested in the topic of the biology and human behavior Robert Sapolsky has some great vids on YouTube.

Thanks to Vince Hustad, UIUC mycologist, for the conversation and article reference that lead to this post. Images courtesy of Katherine Chi (grey kitty) and Laura Stein (b&w kitty).