Cats — those gif-able, meme-driving, better-than-dog pets — are awesome.*
Their poop? Not so much.
It's long been known that some cats carry a parasite called Toxoplasma gondii, or T. gondii, and that they shed an embryonic form of the parasite, called oocysts, in their feces. When transferred to humans, the parasite can cause a disease known as toxoplasmosis, which results in flu-like symptoms and muscle pains that can last for a month or longer.
Now, a new study published in Trends in Parasitology warns that the danger from T. gondii is a far more troublesome and widespread problem than was previously believed. Citing a spike in cat ownership and the parasite's astounding reproduction rate, Dr. E. Fuller Torrey and Dr. Robert H. Yolken, scientists at Johns Hopkins University Medical Center, warn that the T. gondii oocysts "pose a significant public health hazard," especially for children.
T. gondii can only complete its sexual cycle in cats, meaning they're the only animals that spread the parasite's embryos in their feces. But other animals can still be carriers, and cats often pick up the parasites in the first place by eating infected animals in the wild, such as birds.
Once infected, cats then begin to excrete the oocysts for a median of eight days, dropping as many as 810 million of them in their poop. Those oocysts are tough to kill, too, and can remain viable for at least a year and a half under certain conditions.
Further, the study says a sizable increase in the feline population has made it easier for the parasites to spread. Between 1989 and 2006, the number of house cats in the U.S. rose from 54.6 million to 81.7 million. On top of that, there are another estimated 25 million to 60 million feral cats now living in the wild.
All of those cats drop a combined 2.6 billion pounds of poop every year. And though only about 1 percent of cats are thought to be infected at a given time, that still amounts to a lot of infected cat turds.
Indoor cats are far less likely to become infected. Torrey says that "strictly indoor cats really shouldn't be a problem" because they shouldn't encounter or consume the parasites in the wild.
As for outdoor cats? They can pick up the parasites all over the place — and deposit them just about anywhere, too. The study specifically cautions that, because cats can mistake a sandbox for a litter box, those play areas, "and other places favored by cats for defecation," should be assumed "highly infectious" unless they're covered at all times when not in use.
It's a growing concern because T. gondii infections have been linked to some serious health complications in recent years. Studies have shown a correlation between elevated T. gondii levels and schizophrenia, depression, suicidal behavior, obsessive-compulsive disorder, and brain cancer. In pregnant woman, T. gondii infections have been tied to deafness, retinal damage, and mental retardation in fetuses.
However, that doesn't mean you should go swap your cat for a dog. The authors note that T. gondii infections have fallen in humans over the past two decades. And according to the CDC, most humans' immune systems are strong enough to ward off the infections in the first place.
So remember to wash your hands after you scoop your cat's poop. And if you're not doing that already, you probably have more problems to worry about than just T. gondii.
*The author of this post is a cat owner, and still thinks cats are awesome despite their issues with parasites.