Crazy Cat Ladies; is there something to it?
My colleague in Biology, Dr. Bruce Smith, brought me a microbiology story that he thought I might enjoy, via The Atlantic Monthly. His comments to me as he handed me this article printout were
…that magazine is way too liberal for me, but I thought you might like it…
Spot on, Professor Smith, I do like The Atlantic! Thanks for bringing this to my attention, and this is only the second posting where I let my political leanings out (here is the first one ever, and I still think Michelle Bachmann is unfit for office.)
The news article recounts the ongoing research of Dr. Jaroslav Flegr, from Charles University, Prague, Czech Republic, who has proposed that the protozoan parasite Toxoplasma gondii has developed a mechanism for manipulating the behavior of the hosts that it infects. Toxoplasma infections are not new; there is a wide body of medical literature describing the significant effects of the parasite on the developing fetus, and outlining the route of transmission from cat feces into humans. This risk is why I am still changing the litterbox in our house 13 years after the birth of our last child, however I suspect that the risk to the women in the house is significantly diminished currently.
Flegr began by recruiting college students for behavioral tests, and testing them for the presence of Toxoplasma. Infections in the Czech Republic are endemic, with upwards of 30 to 40% of the population having a latent form of the disease. What he concluded after examining large numbers of subjects was that many patients had delayed reaction times in tests, and overall personality types fell into distinct groups. Males with the parasite were typically more “introverted, suspicious, [and] oblivious to other’s opinions” in comparison to uninfected individuals, however females with the parasite were typically much more outgoing and trusting than uninfected women. Flegr continued his studies and found highly reproducible results in civilian and military populations as well.
The behavioral studies conducted by Flegr are intriguing, but without a neurological mechanism to explain them, they at best demonstrate a correlation between an infectious agent and human behavior. What is missing is experimental evidence to show causality between Toxoplasma and these behaviors. Animal models are the solution to this problem, and a number of studies have now been conducted which examine the effects of behavior modification of rodents following Toxoplasma infection. Joanne Webster, of Imperial College London, has show that infected rats are more active and less cautious than uninfected rats. Examination of the brains of infected rats showed that metabolism of the neurotransmitter dopamine was altered in these rats, and that anti-dopaminergic drugs could suppress the observed behavior changes. One additional finding was highly intriguing; when infected rats were put into large cages with defined areas of cat urine, the rats actively sought out and remained at the areas with the cat urine, indicating that the behavioral changes in the rats were making the rats seek out cats and enabling the parasite to return to its definitive host. This has become known as “Fatal Feline Attraction.”
The interview in the Atlantic article concludes with more material from Prof. Flegr, who has recently completed a behavioral study in humans, supporting Fatal Feline Attraction in humans. In a blinded study, he found that infected men like the smell of cat urine, while infected females have the reverse response towards cat urine. Control urine samples included dog, horse, hyena, and tiger(!), and infection had no effect on how those samples were rated. So I’m guessing the reason I am still changing the litterboxes is because I have a latent infection with Toxoplasma, as does my wife who cannot stand the smell of the boxes. Mystery solved!