Dear EarthTalk: How is it that flushing cat litter down the toilet has negatively affected sea otters? What is the responsible way to dispose of cats' waste?
--Margo Boss, San Dimas, CA
According to Dr. Melissa Miller of the California Department of Fish and Game, cat feces can contain Toxoplasma gondii, a parasite that gets into feline systems from the eating of infected rodents, birds or other small animals. When cats later expel these parasites in their droppings--sometimes hundreds of millions at a time--each can survive in soil for over a year and also contaminate drinking water.
Most municipal sewage treatment systems are not designed to filter out Toxoplasma, and so the parasites also get into storm drains and sewage outflows that carry them out to near-shore ocean waters. Here, researchers have found, sea otters prey on mussels, crabs and other filter feeders that can concentrate Toxoplasma. Hundreds of sea otters have been found dead on California beaches in recent years with no obvious external injuries, and Miller and other scientists think that Toxoplasma may be the cause.
There are other possible culprits, too, including toxic algae blooms caused by urea, an ingredient in fertilizer, and the plethora of other man-made pollutants that end up in ocean waters. But California's legislature last year nonetheless passed a bill to protect sea otters, in part by requiring that all cat litter sold in the state carry a warning label advising cat owners to not flush cat litter or dispose of it in storm drains.
Toxoplasma can also cause health problems for people, especially those with compromised immune systems (such as AIDS patients). While not typically fatal in humans, Toxoplasmosis, as the disease is called, can also cause birth defects, blindness and/or brain damage in children born to infected mothers.
The best way to avoid the infection is to use plastic gloves when changing the litter box and to wash hands thoroughly afterwards. It is also advisable to stay away from raw or undercooked meat and uncooked or unwashed vegetables that may have been contaminated by manure (although felines are the parasites' primary host, other warm-blooded animals and birds can also be carriers). Toxoplasmosis doesn't normally spread from person to person (with the exception of pregnant women, who can pass it on to their fetuses), but in rare instances it has contaminated blood transfusions and organs donated for transplantation.
So what's a responsible cat owner to do about dumping the contents of their cat's litter box? According to Dr. Patricia Conrad, a veterinarian and parasitologist at the University of California at Davis who has studied Toxoplasma contamination in sea otters, cat owners can start by keeping their cats inside, where they are not able to hunt the small animals that can pass Toxoplasma along to them in the first place. (Bird lovers have been requesting this for years.)
Those cat owners unwilling to keep their cats inside should do their part by at least not flushing cat litter or cat feces down the toilet. Cat fecal material should be placed in double plastic bags and included in the household trash. As such it will end up in the landfill where precautions are taken to prevent environmental contamination.