Killer Kitty Litter

How a cat can take out a dolphin

by Alan D. McNarie

All of the kitty litter bags sold in California label carry a label that warns cat owners not to flush the litter or dispose of it in storm drains. That law, enacted in 2006, was passed in response to scientific studies linking sea otter deaths to a disease carried through cat feces. Kitty litter sold in Hawai'i is not required to carry such labeling. Yet the same disease that is killing off California's sea otters is also killing Hawaiian wildlife, including monk seals, spinner dolphins, nene and 'alala (Hawaiian crows).

Felines, including the common housecat, are the primary carriers of the parasitic one-celled organism Toxoplasmosis gondii, which causes toxoplasmosis. A recent study of sea otter mortality discovered that T. gondii was responsible for 17 percent of otter deaths. Another study strongly linked the presence of T. gondii in otters to freshwater runoff that likely contained oocysts (egg-like encapsulated forms) of T. gondii. The parasite, which can cause brain lesions, heart disease, blindness and birth defects, can live in many different hosts-but only creates oocysts in felines, which then pass them into the general environment through their feces. The ordinary form of T. gondii dies when exposed to air, but oocysts are extremely tough, able to survive flushing and sewage treatment processes.

One survey of California's Morro Bay watershed discovered that the area, with about 12,000 households and 9,300 cats, was generating 107 tons of cat feces annually; the soil in the watershed was contaminated with 97 oocysts per square meter.

The oocysts are an example of a new type of pollution-pathogen pollution-that researchers are only beginning to understood. As agricultural and urban areas come to dominate watersheds, the parasites and diseases from these new environments are washed downstream, creating threats to creatures that had never experienced those parasites before, or had never experienced them in such concentrations. Like California's off-coast denizens, Hawai'i's native birds and mammals evolved without natural defenses T. gondii pathogens.

Counting crows

In Hawai'i, toxoplasmosis has been found in endangered nene geese and in red-footed boobies, as well as in game birds such as the Erckel's francolin. The hardest-hit local bird may be the 'alala (Hawaiian crow).

The 'alala is one of the rarest birds on earth; there are 56 left in captivity. There are no known 'alala left in the wild. In the 1990s, when there were still a few wild birds left, an effort was made to replenish the wild population by introducing 27 birds raised in captivity. The effort failed, in part because of T. gondii.

According to biologist Paul Banko, who worked on the project, 21 of the released birds died; the rest were recaptured in 1999.

"We were losing them so fast that it just made sense to protect them until we could manage the habitat more effectively," Banko says.

None of the dead birds were proven to have fallen prey to hunting cats; some of the recovered bodies had been chewed, but that may have been by scavengers. However, five of the re-introduced 'alala were known to have caught toxoplasmosis. Four died; a fifth was recaptured and nursed back to health with the aid of antibiotics.

"The toxo was really a surprise to us...," says Banko. "It wasn't just like a fluke or an odd event. It was a repeated source of mortality."

Banko also notes that the disease may have contributed to other 'alala deaths, since a bird weakened by toxoplasmosis was more easily caught by predators or felled by another disease. A similar phenomenon was documented by one of the sea otter studies, which found that otters that had died from shark bites were three times more likely to have toxoplasmosis than were otters in the general population.

"Getting cats out of wild habitats is obviously important for restoration of the species," says Banks, who thinks the 'alala probably got exposed by picking at cat feces in the forest. He and Hess both participated in another study, published this year in Journal of Wildlife Diseases, that discovered that seven percent of the feral cats trapped on Mauna Kea had active cases of toxoplasmosis.

Dead dolphins

For the past 16 years, scientists have known of the danger of toxoplasmosis to another Hawai'i native. A 1991 paper published in Veterinary Pathology found that the disease killed a spinner dolphin in Hawai'i. That study was only one of several that have linked toxoplasmosis to the deaths of dolphins and whales worldwide. An Australian veterinary team found toxoplasmosis in a stillborn Pacific bottlenose dolphin. Another study found it in several different species of dolphins and porpoises, including 58 dolphins that had stranded themselves on Spain's Mediterranean coast. That study also found toxoplasmosis in a long-finned pilot whale.

The disease has also been found in various species of seals, including the endangered Hawaiian monk seal. An article in Journal of Parasitology in 2005 reported the discovery of T. Gondii in a Hawaiian monk seal with visceral and cerebral lesions.

"Anywhere where there are feral cats that are living in colonies around the ocean, it could affect wildlife that are living in the ocean," believes USGS biologist Steve Hess, who has studied the disease's prevalence on this island. "Seawater doesn't kill toxoplasmosis. The toxoplasma organisms can complete their life cycle in a very salty environment."

Now what?

It has been scientifically established that there's an active reservoir of the disease among cats on this island, and that it can infect a number of wildlife species (including some that are critically endangered); for at least one species, it could tip the scale between survival and extinction.

But local government officials seem unaware. The Journal called the State Department of Health to see if there were any rules about the disposal of kitty litter. Nobody had an answer, or even wanted to venture advice; one official said he'd research the topic and call us back, but hadn't done so as of the deadline for this article.

We also asked Nelson Ho, deputy director of the County's Department of Environmental Management, if the County had any regulations or advice about the disposal of kitty litter. Ho was equally surprised by the question, but offered a couple of suggestions.

"To keep it out of harm's way in terms of impacting the public, directly, it should be in the landfill, unless people want to douse it in alcohol or some sort of disinfectant," he said. Even Hilo's unlined landfill was better than dumping it down the toilet or piling it in the back yard, he believed, since the landfill's "leachate," or fluid runoff, was contained and monitored.

He also suggested that those who owned cats within 500 feet of the ocean or of a stream might want to keep their pets indoors.

T. Gondii can also cause diseases-especially birth defects-in humans. Pregnant women and those with compromised immune systems are advised not to handle kitty litter, and to avoid contact with animals with disease symptoms, such as kittens with runny eyes.

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