One of the persistent stories that won’t go away is that your cat will make you crazy by infecting you with toxoplasmosis. In our clickbait internet culture, sensational headlines about “Your Cat is Making You Crazy” are sure to bring in the readers, so the story continues to pop up again and again, slowly turning into an urban myth. Like most urban myths, what started with a grain of truth is wrapped in a whole lot of not-so-true.

What is Toxoplasmosis, Anyhow?

A single-celled parasite called Toxoplasmosa gondii causes a disease called toxoplasmosis, which infects an estimated 60 million people in the US. Healthy immune systems keep the parasite from causing illness, so very few people actually have symptoms. However, pregnant women and those with poor immune systems are told to be cautious.

People can be exposed to T. gondii from:

• Eating undercooked, contaminated meat (especially pork, lamb, or venison)
• Accidentally ingesting contaminated meat due to cross-contamination (handling it and not washing your hands thoroughly, using cutting boards and utensils on undercooked meat and then using them for other food without properly sanitizing them)
• Drinking contaminated water
• Accidentally ingesting the parasite after cleaning a litter box of a cat who is shedding T. gondii and not cleaning your hands or other surfaces that feces comes into contact with
• Accidentally ingesting contaminated soil by not washing your hands after gardening, or by eating unwashed fruit or vegetables from a garden
• Mothers can infect unborn children
• Infected blood transplants or organ transplants
• Unprotected sexual intercourse with a partner infected with toxoplasmosis

Since infected cats shed the oocysts that contain the parasite in their feces, pregnant women are warned by their healthcare providers to take extra precautions about cleaning their cat’s litterbox to prevent potential infection, so many women have already heard of toxoplasmosis through their doctor.

How this Story Got Started on the Internet

A pair of studies were published in the past few years that helped excite a lot of clickbait headlines.

A 2012 study, Brain cancer mortality rates increase with Tosoplama gondii seroprevalence in France, noted that in France, regional mortality rates were higher where the level of T. gondii parasite was higher in the population. Headlines around the world insisted that your cat was going to kill you with toxoplasmosis, despite the fact that this wasn’t the conclusion of the study at all. The study also pointed out that T. gondii prevalanence in pregnant women were lowered over a twelve-year period, probably due to improvements in meat production that reduced contaminants, and that brain cancer related deaths have increased over time due to science’s ability to detect brain cancer. The study’s conclusion said “this novel evidence of a significant statistical association between T. gondii infection and brain cancer does not demonstrate causation,” and the authors called for further research. The actual conclusion of the study was lost in the sensational headlines and not mentioned in the stories carried in the worldwide media.

A study published in 2015, Is childhood cat ownership a risk factor for schizophrenia later in life?, caused similar, overly-sensational stories that are still showing up in popular science magazines and web sites. This study cited answers from a previous questionnaire and concluded that individuals with mental illnesses were more likely to have had a cat in their home when they were children. Since the study didn’t account for the many other variables in the children’s homes, the study itself said, “We urge our colleagues to try and replicate these findings to clarify whether childhood cat ownership is truly a risk factor for later schizophrenia.” Unfortunately, once more, the media ignored this conclusion in the interest of telling a more interesting story.

Why do these stories go racing around the internet? Bad journalism.

Why Your Cat Won’t Make You Crazy or Give You Brain Cancer

If you’re still convinced that T. gondii is the problem and that it will cause mental health issues and/or brain cancer, your cat still isn’t to blame.

Cats aren’t the way that people are exposed to T. gondii come into contact with it. Humans most commonly contract it by eating undercooked meat that contains T. gondii in the tissue. Contact with contaminated soil (combined with poor hygiene) and eating unwashed vegetables are also significant risk factors.

If your cat is exposed to T. gondii, she acquires immunity and isn’t likely to become infected unless she has an immune problem. So if kitty does become infected, she only passes oocysts containing the T. gondii parasite for two weeks, ever. After your cat leaves feces in the litterbox, the oocysts in the feces incubate for one to five days before they open and are infectious. This means if you scoop your cat’s litterbox once a day, even if your cat is shedding the T. gondii parasite, you’re getting it out of there before it could infect anyone else. (You’re scooping the litter box every day anyhow, aren’t you? If not, your cats will thank you!)

If You’re Still Worried about Toxoplasmosis

It’s unlikely that you will contract toxoplasmosis from your cat, but if you are pregnant or have a compromised immune system, it’s a good idea to be careful. To reduce your risk:

• Avoid undercooked meat.
• Wash all uncooked vegetables thoroughly.
• Wash all cutting boards and utensils that might have come in contact with meat before using them.
• Wear gloves when gardening or working in soil for other reasons. If you don’t wear gloves, wash your hands thoroughly afterward
• Ask your spouse, friends, or neighbors to help out with litter box duties while you’re pregnant. Alternatively, wear rubber gloves when changing the litter and thoroughly wash your hands afterward.
• Scoop your cat’s litter every day.
• Keep your cat indoors to prevent your cat from being exposed to T. gondii.

What Can You Do about these Stories

The biggest thing we have to fear from scary headlines about our cats making us crazy or giving us brain cancer is the spread of misinformation.

When you see a scary headline, take a moment to do a little research and see whether it’s true before sharing it on Facebook or forwarding it to all of your friends in email. Refusing to share and being knowledgeable enough to let others know that they are sharing bad information is the only way to stop rewarding the media for their misinformed, sensationalist headlines that can hurt cats or leave them homeless.

Updated January 2016 to add reference to sexual transmission.

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Research and Further Reading

Centers for Disease Control and Prevention, Toxoplasmosis FAQ
Humane Society of the US, Pregnancy and Toxoplasmosis
Journal of the Schizophrenia International Research Society, Is childhood cat ownership a risk factor for schizophrenia later in life?
Journal of Molecular Epidemiology and Evolutionary Genetics in Infectious Diseases, Brain cancer mortality rates increase with Toxoplama gondii seroprevalence in France
The Royal Society Biology Letters, Cat ownership is neither a strong predictor of Toxoplamsa gondii infection nor a risk factor for brain cancerMedical Hypotheses Journal, Toxoplasmosis can be a sexually transmitted infection with serious clinical consequences. Not all routes of infection are created equal

Photo credits:

Wikimedia Commons/Toxoplasmosis
depositphotos/DepositNovic
depositphotos/cynoclub
depositphotos/HASLOO