Who would have thought that cats, of all things, are one of Hawaiian monk seals’ biggest threats? But it’s true. Since 2001, the cat-spreading disease toxoplasmosis has killed 11 monk seals in the main Hawaiian Islands. Because the poison acts quickly, not all seals that die from toxo are found. Researchers believe the true number of toxoplasmosis mortalities is higher.

Eleven fatalities may not sound like a catastrophe, but eight of those dead seals were females, one pregnant, meaning the loss of future generations. With only about 1,400 monk seals left in the world (300 in the main Hawaiian Islands and 1,100 in the Northwestern Hawaiian Islands), this is a huge hit.

Nearly all warm-blooded animals, including humans, can get Toxoplasma parasites in their muscles, but the one-celled organism reproduces only in cat intestines. When an infected cat poops, it drops millions of live, fertile toxo eggs in weather-resistant capsules onto soil and plants.

In warm, humid climates such as ours, Toxoplasma egg capsules can remain infective for a year or longer. Foraging mice, rats, birds and mongooses eat the eggs, which form cysts in the animals’ muscles.

Some infected animals get sick and die and some don’t, but their feces are not infectious. The problem comes when a cat, a top-notch predator, eats an animal with toxo cysts. The parasites in the prey’s cysts reach the cat’s intestines, reproduce and the cycle starts over.

Because Oahu alone hosts between 50,000 and 300,000 feral cats, their toxo-laden feces range from mountains to shorelines. Rainwater and runoff wash the infectious eggs into gutters, streams and coastal waters. Seals get infected by swimming in contaminated water and eating infected prey.

Besides killing our native seals and birds (nene also die from toxo), this cat-dependent parasite can cause fetal death or birth defects in pregnant, and trying-to-get- pregnant, women. Toxoplasmosis has no treatment and no vaccine.

Cat owners can help reduce the spread of this disease by keeping pet cats exclusively indoors, a gift also to our native birds, which cats kill routinely. Spay and neuter your house cats, and take unwanted kittens to a shelter where someone may adopt them. It’s illegal to abandon cats outdoors.

The scientific literature overwhelmingly shows that the good-intentioned idea to trap, neuter and release (TNR) feral cats does not reduce populations, because TNR isn’t done in enclosed systems.

Feeding feral cats exacerbates the problem. People for the Ethical Treatment of Animals (PETA) agrees, stating that neither “managed” (meaning fed) colonies nor TNR are humane treatments of feral cats. The most compassionate answer to the devastating feral cat problem is euthanasia.

As you read this, I’ll be visiting Australia, where the government has launched a program to kill 2 million feral cats to save the country’s threatened native species. Hawaii should do the same.

To reach Susan Scott, go to www.susanscott.net and click on “Contact” at the top of her home page.