Microbe of the Month — Ultra Creepy October Edition in Honor of Halloween

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Do you like cats? I happen to love them. I am the proud guardian of two cute fuzzballs myself. Our featured microbe for the October edition of Microbe of the Month has a special relationship with our feline friends. This is a little bit creepy in honor of Halloween so stop reading now if you scare easily.

There is a microorganism called Toxoplasma gondii that is found in cat feces. Serological studies suggest that almost one third of the global population has been exposed to and may be chronically infected with this parasite. Infection is typically asymptomatic in healthy adults.

T. gondii also has a special relationship with rodents (mice, rats, etc.) In fact, it has been shown to alter the behavior of infected rodents in a very peculiar way. Essentially infected rodents display a significantly reduced aversion/fear to the smell of cat urine. Because of this the chances of them becoming prey of any particular cat is greatly increased. Cats are the only hosts within which T. gondii can sexually reproduce to begin and complete its life cycle. Therefore it is hypothesized that these behavioral manipulations have evolved as a way for the parasite to propagate itself and continue its existence.

Cool you may be thinking to yourself. Smart little parasite. Here is where things get a bit creepy. A number of studies have suggested subtle behavioral or personality changes may also occur in infected humans (remember how many humans are probably infected as described above). Infection with the parasite has been associated with a number of neurological disorders, particularly schizophrenia. At this time direct evidence of a causal link remains limited (aka; there is none) but a ton (very little) of work is ongoing exploring this possibility. The phenomenon of the “crazy cat lady” has been attributed to severe infection with T. gondii in the female brain (attributed by me).

Of course I have had cats my entire life and I am totally sane (lol) so I highly doubt the connection. The next time you are emptying your cat’s litter box remember to cover your nose or wear a mask. If you are not already infected with T. gondii (sorry but it is probably too late) then you soon will be. If you ever find yourself in a mental hospital or insane asylum and the doctor’s ask how you got there, tell them it was because of your cats and an invisible parasite that you were infected with which altered your brain chemistry and made you crazy. At that point they will surely let you out of the straight jacket and send you on your merry way.

Happy Halloween and cheers!

Trivia challenge for October: How many species of Listeria are there? Easy one right? Don’t bother checking the [redacted] SOP. It is wrong. That said as with most things in science the answer is not as straightforward as you might think. In fact there are at least three “correct” answers and possibly a fourth if you are really clever. I will reveal the fourth answer now: It’s complicated. The deadline for your answer submission is Oct 31 at midnight EST. As per usual the most well documented and thorough answer will be the winner. You know the drill by now on the prizes. Admiration and respect..blah..blah…blah..gift certificate! Good luck!

Daniel R. DeMarco, Ph.D.

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