The CATalyst: Toxoplasmosis and “Cat Ladies” in the News Again. What Are the Facts?

Steve Dale, CAT FANCY writer and syndicated newspaper pet columnist, provides a weekly cat news roundup. This week, he discusses recent news stories on Toxoplasma gondii and what to believe.

Did you hear the CNN news report about the woman who, after routinely scooping her cats’ litterboxes, ran toward an open window to leap out?

Am I the only person missing this story?

Of course, that story never happened. But if you read some internet headlines you’d think cats are causing suicides — all but pushing their owners out windows or handing them knives to slash themselves.

According to Science Daily (and other sources) researchers learned that women infected with the parasite Toxoplasma gondii, which is spread through contact with cat feces or eating undercooked meat or unwashed vegetables, are at increased risk of attempting suicide. This is according to a new study of more than 45,000 women in Denmark that was just published in the Archives of General Psychiatry.

Susan Logan, CAT FANCY editor, is a journalist – she seeks the truth. Here’s a part of what she said in her blog on toxoplasmosis. “If Toxoplasma gondii is linked to mental illness and suicide, then people need to know the facts about the infection. Using scare tactics in headlines and slanting the stories to gain the most internet traffic and highest rankings doesn’t help and it can only hurt.”

Let’s Look At The Facts
For starters T. gondii is a protozoal organism that infects most warm blood animals, but domestic and wild cats are the sole hosts which the entire life cycle of the parasite can be completed.

It’s true the study from Denmark did demonstrate that women infected with toxoplasmosis were over-represented for suicides at a rate that was one and a half times higher than for women who weren’t infected. This is compelling.

Dr. Teodor Postolache, associate professor of psychiatry and director of the Mood and Anxiety Program at the University of Maryland School of Medicine and colleagues, found that the risk of suicide seemed to increase with increasing antibody level. So, the more antibodies found in the blood reacting to T. gondii (which relates to previous exposure), the higher the risk of a suicide attempt. Certainly, I understand the associated implication between the parasite infection and suicide.

Still – how do you explain that there are 90 million pet cats in America, and an estimated over 500 million around the globe. Yet, there isn’t one verified published report of a suicide directly related to toxoplasmosis, let alone T. gondii transmitted via a cat.

These sorts of findings are common in science. While the implication is clear, there is also no clear correlation between toxoplasmosis and the increased risk of suicide. In others words, an estimated one half or more of all women in Denmark report a positive antibody for the parasite. So, are these results truly as significant as they first appear?

Also what is the relevancy of cats? At least in the United States most cats are now indoors only, and are therefore less likely to carry the parasite. In his textbook “The Feline Patient,” Gary Norsworthy, DVM, suggests about a third of U.S. cats are infected. I don’t have data on the percentage of cats infected with T. gondii in Denmark.

So how do you explain exposure in people when they have never scooped a litterbox in their life (this is where the parasite is potentially infectious in homes)?

Where Toxoplasmosis Comes From
According to the Centers for Disease Control and Prevention, the most common sources of toxoplasmosis (in America) are undercooked meat and unwashed vegetables. People can also get toxoplasmosis by gardening, digging in the dirt where another animal left infected feces.

Certainly, though, the parasite is abundant. According to Science Daily, about one-third of the world’s population is infected with the T. gondii parasite and that number is likely higher in America.

The most significant known health risk of a human becoming infected is for pregnant women in her first trimester; the infection passed to an unborn baby at this time may cause severe birth defects or death. Although, immune comprised individuals, young children and the elderly may become ill from toxoplasmosis, most people are asymptomatic – at least physically.

This isn’t the first time scientists have associated mental illness (schizophrenia, in particular) with T. gondii, and similarly implicate cats (there was a report in March in the Atlantic, for example). Maybe there is something to the possibility that the T. gondii parasite can affect human brains in ways that scientists don’t clearly understand. Until we do understand, there’s no evidence to support scaring cat owners, it only arouses cat haters.

For more on toxoplasmosis and pregnancy, click here.

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