Protecting Yourself Around Furry Felines

Toxoplasmosis infection risk from cat feces can be reduced through healthy human behaviors

/ Author:  / Reviewed by: Robert Carlson, M.D

It's been said there are two types of people in the world: cat people and dog people. Whichever one you are, it's still important to know about an infection that can exist wherever cats exist, especially strays.

The infection is called toxoplasmosis, and it's caused by a parasite that can be found in cat feces.

Infection rates appear to be decreasing for this infection currently. Yet ordinary people can make the infection even less common by following some healthy practices and behaviors.

A recent paper outlined what researchers know about this parasite, the infection it causes and ways to prevent infection in humans.

This paper was written by E. Fuller Torrey, MD, of The Stanley Medical Research Institute in Chevy Chase, MD, and Robert H. Yolken, MD, from Johns Hopkins University Medical Center. They discussed the risks associated with cat feces and infection with the Toxoplasma gondii parasite.

What Is This Parasite?

T. gondii is a parasite that can live in raw or undercooked meat and can be found in cat feces, especially that of outdoor cats.

In fact, the parasite can only complete its life cycle in the host body of a cat, and cats usually become infected when they hunt and eat a small bird or mammal.

It is actually not uncommon for people to already carry this parasite in their bodies. More than 60 million people in the US are estimated to be infected with the parasite, but their immune systems keep it in check.

However, the parasite can cause a serious infection caused toxoplasmosis in those with weakened immune systems or in women who are pregnant.

An infection can include flu-like symptoms, but more severe ones can cause brain damage or harm to the eyes and other organs. The infection can also be fatal.

"When T. gondii infects previously [uninfected] pregnant women it may cause a congenital syndrome that includes deafness, seizures, retinal damage and mental retardation in the fetus or [newborn]," the authors wrote.
In those with compromised immune systems, such as people with HIV or those undergoing chemotherapy, an infection can cause severe central nervous system damage.

How Do Humans Get Infected?

In this paper, the authors discuss the risk of T. gondii transmission given the amount of cat feces that humans may be exposed to. The authors estimate that 1.2 million metric tons of cat feces are dropped on US soil each year.

They estimate that the number of T. gondii eggs ranges from three to 434 per square foot of soil, with higher amounts in areas with more cat poop.

It's therefore possible that the parasite could be transmitted from cat feces in the soil, grass, animal feed, water or elsewhere into human food that is not thoroughly cooked (which kills the parasite).

The authors also note that humans may come into contact with the parasite by ingesting or inhaling the T. gondii eggs directly.

"This may occur when they are changing the litter box of a cat, gardening, playing in a sandbox, eating unwashed fruits or vegetables or drinking water containing [eggs]," the authors wrote.

They added that cockroaches and flies may carry the eggs from cat feces to unprotected food, and pet dogs who have eaten or rolled in cat feces may transmit the eggs to people.

Children playing in unprotected sandboxes that cats may have used as a litter box may be more at risk for contracting the parasite because they frequently put their hands in their mouths, the authors noted.

You Can Reduce the Risk of Infection

There are a number of things people can do to reduce the risk that they or their family members will become infected with the parasite.

"First, it should be assumed that the play areas of children, especially sandboxes, are highly infectious unless they have been covered at all times when not in use or are located in a protected area not accessible to cats," the authors wrote.

"If in doubt, sand in sandboxes should be replaced and protective barriers put in place," they wrote. "Covered and protected sandboxes have been demonstrated to remain uninfected."

The authors also suggested that gardeners wear gloves and thoroughly wash their hands after gardening if their gardens may be accessible to cats.

The authors wrote that reducing stray cat populations and keeping pet cats indoors where they cannot hunt small animals could also help reduce the risk of the parasite's transmission to humans.

Cat owners can reduce their risk by following hygienic practices with their cats' litter boxes.

The Centers for Disease Control and Prevention (CDC) recommend that cat litter boxes be changed daily in the homes of individuals who may be at risk for infection.

"The Toxoplasma parasite does not become infectious until 1 to 5 days after it is shed in a cat's feces," the CDC states.

Those who are pregnant or immunocompromised should avoid changing cat litter as much as possible.

If they must change the cat litter, they should wear disposable gloves and wash their hands thoroughly with soap and water afterward.

The CDC also recommends keeping cats indoors, not adopting or handling stray cats (especially kittens) and not getting a new cat while you are pregnant.

Not feeding cats raw or undercooked meats will also reduce the risk, as will keeping outdoor sandboxes covered so that stray cats cannot use them as litter.

Cats, like dogs, can be some people's best friends. And, like all animals, they can carry parasites. But there are many ways humans can protect themselves while enjoying the company of their furry felines.

The study by Drs. Torrey and Yolken was published July 9 in the journal Trends in Parasitology. Information regarding funding and disclosures was unavailable.

Review Date: 
July 9, 2013