Are Parasites Taking Over Our Brains and How Does Your Pet Cat Fit Into the Picture?

John McManamy Health Guide
  • A few days ago I watched a new TED Talk, “Suicidal crickets, zombie roaches and other parasite tales.” The talk was delivered by science writer Ed Yong.


    So here you are, a certain type of brine shrimp. A tape worm infects you and hijacks your brain so you socialize in a swarm with other infected shrimp. It also turns you red. Next thing, you are eaten by a flamingo. 


    It seems the tapeworm needs the inside of a flamingo in order to reproduce. Essentially, the tape worm has turned you and your fellow brine shrimp into one very conspicuous floating buffet.


    Parasites come in many forms. According to Mr Yong: “Manipulation is not an oddity. It is a critical and common part of the world around us.” Of special interest to us is the single-cell organism, toxoplasma gondii (T gondii or toxo), which has found its way into one-third of the human brains on the planet.

    Add This Infographic to Your Website or Blog With This Code:


    Toxo infects a wide variety of mammals, but can only reproduce in a cat. If toxo gets into a rat or mouse, it effectively turns the rodent into a cat-seeking missile. When the rodent smells cat pee, it runs TOWARD the cat in order to get eaten.


    According to Mr Yong, “It’s a classic tale of eat prey, love.”


    Not to worry you, but Mr Yong points out that a single-cell organism is manipulating a mammal with a brain very similar to ours. 


    There is some evidence that people with toxo score slightly differently on personality tests and may be more inclined to suicide, though it would be highly premature to regard these results as conclusive.


    There is also the suggestion that toxo may be responsible for schizophrenia in a small portion of those who have this illness.


    The major proponent of the toxo-schizophrenia connection is Fuller Torrey, who heads up the Stanley Medical Research Institute. Dr Torrey is better known as an outspoken mental health advocate, which has earned him adulation and contempt in equal measure. (Disclosure: Dr Torrey wrote a glowing back cover blurb for my book, Living Well with Depression and Bipolar Disorder.)


    Dr Torrey argues that the rise in incidences of schizophrenia coincides with the widespread domestication of cats in the late 18th century. We now have about 90 million pet cats in the US, plus about 70 million feral cats.


    We know that cats shed embryonic toxos called oocysts in their feces, which then infect humans. This includes children and even fetuses through the mother. The toxo may remain dormant in its host’s brain for 10 or 20 years. 


    We are a long way from establishing a definitive toxo-schizophrenia connection, and Dr Torrey would be the first to acknowledge this. In the meantime, a sampling of news headlines from July 2013, in the wake of a review study by Dr Torrey:

    • Is Cat Poop Dangerous? CNN 
    • Harmful Parasites in Cat Poop are Widespread. NPR 
    • Parasites in Cat Poop: How Dangerous Is It? MSN

    Another parasite contender is the borna virus, which infects horses and cattle and other mammals, including humans. A number of studies suggest a link between the virus and mental illness, though a 2012 study casts doubt.


    Add This Infographic to Your Website or Blog With This Code:

    Maybe, with further study, we will discover that we have nothing to worry about. But we must bear in mind that much of our world is invisible to us, and that we have been paying very little attention to it. We all talk about things that may be eating away at our minds. Perhaps one day we will discover how literal we actually were.

Published On: March 30, 2014