Raccoon Toilets Sanitary for Critters, Deadly for Humans

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Raccoons create latrines, particular locations that visit they repeatedly. While this practice may be sanitary for the animals, humans – particularly small children prone to putting strange objects in their mouths – can contract a deadly, parasitic roundworm when they encounter these animal outhouses.

However, recent research may have struck upon a prevention strategy. The study found that sterilizing these latrines and leaving out medicated bait for the raccoons – as is done to control rabies – can reduce the presence of the parasite. [Pitcher Plants Double as Toilets]

There are only 18 known cases when the worm, Baylisascaris procyonis, has infected humans, and all occurred in North America. However, infection doesn't become obvious until the worm's larvae move into a victim's eyes or central nervous system, where they cause blindness, permanent neurological damage, or death. As a result, it's possible cases have escaped detection, according to Kristen Page, a disease ecologist at Wheaton College in Illinois and the lead author of a paper published in the January issue of the journal Emerging Infectious Diseases.

"I think it's important to not scare people, but to teach them how to clean up and make sure they keep their play area safe. It's most dangerous for toddlers or kids who are putting things in their mouths," Page said.

There are multiple ideas as to why raccoons create latrines, which multiple animals use to defecate repeatedly, including as a means of communication or sanitation, she said.

In an earlier study, Page and her colleagues found the parasite's eggs in 14 of 61 raccoon latrines located in 119 suburban Chicago properties near forest preserves. Raccoon feces have about the same diameter as a thumb, and the researchers frequently found them on raised, flat surfaces, such as decks, a tree house, flat roofs, landscaping rocks and concrete retaining walls.

In the more recent study, the researchers went to a rural area in the Upper Wabash Basin in north central Indiana and selected 16 patches, and in half of these (called the treatment patches) they removed and sterilized all the latrines they could find. The researchers also distributed anti-roundworm medicine disguised in fishmeal and marshmallow bait, and captured mice to test for the parasite.

Humans are an accidental host for B. procyonis. The worm spends the adult part of its life cycle reproducing within the raccoons, which defecate its eggs. If things go according to plan, another animal, like a mouse or bird, consumes the eggs, and the larvae hatch and form cysts within these animals' tissues. When a raccoon eats the smaller animal, it becomes infected with the larvae, which become adult, egg-laying worms.

Between March 2007 and November 2008, the occurrence of the eggs in raccoon feces declined by more than threefold. After about a year of baiting, the researchers also saw the occurrence of the larvae in mice decline from 38 percent in the control patches to 27 percent in the treatment patches.

"Implementation of baiting strategies, in conjunction with traditional raccoon management on public lands, could reduce the risk for transmission on nearby private properties," they wrote.

To remove a latrine, Page gives the following instructions: Wear gloves and carefully put the feces in a garbage bag. If the latrine is large or appears old and dry, remove an inch or two of the soil with the feces. Then, treat the area with heat, by pouring boiling water over it. Chemicals and cleaning agents don't work.  

You can follow LiveScience writer Wynne Parry on Twitter @Wynne_Parry.

Wynne Parry
Wynne Parry
Wynne was a reporter at The Stamford Advocate. She has interned at Discover magazine and has freelanced for The New York Times and Scientific American's web site. She has a masters in journalism from Columbia University and a bachelor's degree in biology from the University of Utah.