peril from cats is exaggerated
Felines were long thought to pose a high risk of transmitting toxoplasmosis, but that has been disproven.
By Denise Flaim
February 21, 2005
The woman called with a bittersweet announcement.
The good news: She was pregnant. The bad news: She was returning the kitten
she had bought from Joan Bernstein, who breeds Tonkinese cats in Center
Along with admonitions to avoid alcohol and hot tubs, pregnant women are
always warned about contact with cats, because of the concern that feline feces
can transmit toxoplasmosis.
According to the Centers for Disease Control and Prevention, more than 60
million Americans carry the Toxoplasma gondii parasite. Those with healthy
immune systems often do not notice, exhibiting mild flu-like symptoms or none at
But an active toxoplasma infection during pregnancy can cause blindness and
brain damage in the unborn infant, as well as stillbirth or preterm labor.
Bernstein told her caller that there was no need for her to part with the
cat if she followed a few simple precautions: Wear a surgical mask and gloves
when cleaning the litter box, or, better yet, have her husband do it.
Although the current conventional wisdom among doctors is that pregnant
women who take adequate precautions against toxoplasmosis need not give up their
cats, some women still get that unfortunate message.
And some experts go so far as to say that cats have been unfairly singled
out for spreading this highly infectious disease, when in fact they carry
"The chance of a pregnant woman catching toxoplasmosis from her cat is
extremely rare," says veterinarian James Richards, director of the Feline Health
Center at the College of Veterinary Medicine at Cornell University in Ithaca,
As proof, he points to a study done in six European cities and published in
the July 2000 issue of the British Medical Journal. It found, he says, "no
association between toxoplasmosis and having a cat, litter box cleaning or
having a cat that hunts."
Instead, the study concluded that the main risk factors for acute
toxoplasmosis infection were eating undercooked lamb, beef or game (30% to 63% of
infections), contact with soil (6% to 17%), and travel outside Europe and North
America. "Contact with cats," the study concluded, "was not a risk factor."
But many doctors still focus on them. A report in the December issue of
Contemporary OB/GYN magazine found that of the 1,459 doctors responding, 1,364
advised that their cat-owning patients not clean the litter box. But only 1,101
mentioned avoiding raw or undercooked meat, and only 888 recommended gloves
for gardening — even though those activities represented a greater risk of
Feline scapegoating started, Richards explains, when "it was discovered that
cats shed infectious stages of toxoplasmosis in their stool. It's from that
that all this fear arose."
Cats can become infected with toxoplasmosis by eating or licking cat feces
that contain the parasite egg, or oocyst.
But Richards says that scenario is "unlikely" and suggests that predation —
killing and eating infected mice, birds and other small animals — is the main
way cats get infected. So keeping a cat indoors dramatically cuts down the
risk of transmission.
Even then, the window for passing the disease on to humans is a relatively
"Once cats are infected, they will for a short period shed these
toxo-organisms in their stool — maybe for a week or two," Richards explains. "And the
instant they are shed, they are not infectious. They have to mature for a day
or more before they are."
Which means that frequent cleaning and scooping of a litter box — always
with gloves if a woman is pregnant — lowers the negligible risk even further.
Casual contact with an infected cat is not considered particularly risky, as
the parasite is not usually carried on the fur.