Now, when there's a study about cats and humans, and the "t-word" (Toxoplasmosis) comes up, alarm bells start ringing in my head. Toxoplasmosis is a disease caused by T. gondii, and current estimates suggest that one out of three humans is a carrier. It is typically only a threat to pregnant women and those with compromised immune systems. While many people are infected and have no symptoms or ill effects, it can cause flu–like symptoms, and even eye or brain damage. Because T. gondii can only reproduce in a feline digestive system, this disease is rightly associated with the presence of cats.
However, there are good reasons that placing the blame for Toxoplasmosis on cat ownership raises my hackles. No direct relationship between cat ownership and toxoplasmosis has been found, and the CDC does not consider cat ownership a risk factor for infection with T. gondii.While I have no doubt that cats are ultimately a huge contributor to toxo due to how T. gondiireproduces, toxo is most likely contracted by handling raw meat or unwashed vegetables that were grown in contaminated soil. Furthermore, cat bites are not considered a means of transmitting Toxoplasmosis.
As usual, the media had a field day with the conclusion that Toxoplasmosis may be a contributor to the depression risk:
- "...the most likely possibility is actually that cat bites can transfer the bacteria Toxoplasma gondii to their human owners." –Geekosystem (despite the fact that the study also found that people were more likely to be treated for depression first, not the cat bite)
- "A third, more science-y hypothesis relies heavily on the bacterial composition of cat poop. You see, a parasite called Toxoplasma gondii, commonly found in cat feces, might be infecting the brains of cat owners." – Boston.com
- "One cat infected a patient with Toxoplasma gondii - a nasty little parasite that can literally rewire the human brain. And there's nothing quite like kitty daggers to make sure you get a full serving." – Huffington Post (even though FECES, not bites are what likely transmits the virus)
Even Smithsonian.com fell for the toxo-bait. Reporters, that's an EPIC FELINE FAIL.
So while we can toss out toxo as a good explanation for "cat bite depression," it is important that we look at how serious this cat bite-depression relationship is in the first place.
To think a little more critically about this, let's consider the actual risk as a cat owner of being bitten and depressed. Out of the 1.3 million patients included in this study, 750 had cat bites, and of those, 310 were also treated for depression. One hundred and seventy four of those people were bitten by their own cat. But how many of the total patient population owns a cat? If these patients were anything like the general public (of whom around 39 percent own at least one cat), then out of 1.3 million patients, approximately 507,000 of them would own a cat. So out of all those potential cat owners, less than .0004 percent of them were bitten AND depressed. So how strong does that relationship seem now?