Cradles & Cat Poop & Parasites

NDSU Microbiology
by NDSU Microbiology

Guest Blogger, Mitch Maki, VMS Undergrad

If you can’t handle the smell of Whisker’s excrement anymore; if you need a break from that scooping-the-litterbox chore; and if, by chance, you are a woman, then I have a scheme for you: it might be time for you to start (or expand) your family.

The link between having a baby and passing off the task of scooping cat poop is the tiny, single-celled Toxoplasma gondii parasite. This microorganism lives inside cats, and its oocysts can be shed in their fecal matter where they can spread to a human host. Although it isn’t a danger to most healthy people, unborn babies can be at serious risk for birth defects from this parasite, and new research into the parasite shows some connections to some interesting neurological conditions.

It’s estimated that 30% of the human population is carrying the Toxoplasma parasite inside them. The good news is that as long as your immune system is in good shape, your body fights off the parasite which then goes into a dormant phase where it resides in brain, bone, and heart cells but causes no illness. If an immunocompromised person (eg, someone with HIV/AIDS or transplant patients) acquires the parasite it can cause small symptoms such as swollen lymph nodes and muscle soreness, but can also cause more detrimental conditions if not treated, such as multifocal necrotizing encephalitis (lesions on the brain that can lead to severe health problems: coma, convulsions, or even death).

So those of us with healthy immune systems have nothing to worry about, right? It’s not quite that simple. Even if you’re perfectly healthy, if you are a woman who is currently pregnant, cat feces must be avoided. This parasite will not affect a
healthy pregnant woman, but the unborn child can have some serious birth defects if the parasite is acquired during the pregnancy. If Toxoplasma enters the human host early in the pregnancy, the central nervous system of the baby can be greatly
affected. Luckily, if a mother gets the parasite before getting pregnant, her immunity is passed along to her child.

Although affecting the health of the fetus is the most common way that Toxoplasma affects human health, there is more evidence now that the dormant parasite can have an effect on our neurological state. It has been known for a while now that the parasite affects the behavior of its secondary host. If a rat becomes infected, it begins to act fearless and even amorous toward cats (this usually does not end well for the rat). The life cycle of the parasite has to go through the cat, so it has developed to control its secondary hosts in order to ensure its survival.

Humans, on the other hand, are a dead-end host for Toxoplasma. Because cats don’t eat humans (although mine makes an attempt whenever she isn’t fed on time), once the parasite enters a human, its life cycle is at an end. This led researchers to hypothesize that there were no neurological affects on humans like there were with rats or birds. This view is starting to change as more research is being done on how humans infected with Toxoplasma act differently.

Preliminary studies show that women who are infected with Toxoplasma can be more outgoing, trusting, and rule abiding, while
men who are infected portray opposite effects such as being introverted, suspicious, and non-rule abiding.Toxoplasma has been linked to things such as schizophrenia, suicidal thoughts, increased traffic accidents, OCD, and even Alzheimer’s. There is currently research being done to look more deeply into these links to see if Toxoplasma could be responsible for many cases of schizophrenia and other neurological conditions.

The research on Toxoplasma’s effect on our brains is new, and some people are critical of this different way of looking at brain conditions. It seems crazy to blame a neurological disease on a parasite. But there is evidence of a link, so don’t make any quick judgments until more work is done. And no matter what your opinion on “mind-altering” parasites is, if you are pregnant, stay away from the litter box, and just hang out with your furry friend in non-poop situations.

Image: Ke Hu and John Murray; Creative Commons

This entry is part of the MICR 354 (Scientific Writing) student-blog series.