Raccoons Using Toilets

Baylisascaris procyonis: proper name of the raccoon roundworm. Physicians specializing in brain disease know all about Baylisascaris and its deadly effects on humans. People are coming into contact with wild animals on an ever-increasing basis, so you’d be wise to learn a bit about Baylisascaris, too.

This parasite lives in the intestine of the common raccoon, laying millions of eggs which exit the host via defecation. Roundworm eggs are microscopic and sticky, as well as virtually indestructible, so they invariably survive to contaminate another host. When ingested by a second raccoon, they hatch and mature, then begin laying eggs of their own. Raccoons are hardy animals and generally get along pretty well with forty or fifty roundworms inside; in fact, research shows that about 90% of healthy-appearing raccoons are infested with this parasite.

It’s an entirely different story, though, when those eggs are ingested by a non-raccoon individual. The hatching larvae quickly realize that they are not in familiar surroundings. Instead of peacefully remaining in the small intestine, they begin to migrate all through this new host’s body. Frequently, they end up in the brain, and that event is usually fatal. Just one other species on this continent can carry Baylisascaris worms without ill effect, allowing the parasite to disperse its eggs freely. That animal is the domestic dog.

Is this genuinely a risk to human beings? Well, that’s where the raccoon latrine comes in. Raccoon instinct dictates that they defecate in specific areas, called latrines. Such areas are “hot spots” containing millions upon millions of roundworm eggs, which have been accumulating for years since they are essentially impervious to the weather. Furthermore, did you know that raccoons actually prefer to live near humans? Biologists estimate their population density at greater than 100 raccoons per square mile within the New York City limits, roughly three times as many as you’d find in silent, unpolluted forest. So a raccoon latrine could be encountered on a hike or camping trip, certainly, but also during a backyard barbecue, playground excursion, landscaping project, or even in your own drafty attic. Humans stumbling upon a latrine often don’t recognize the danger, and children face the greatest risk due to their typically careless hand hygiene.

Baylisascaris eggs are extremely difficult to clean up (most sources suggest a propane torch for this purpose), so an ounce of prevention here is highly recommended. Seal up your attic and garage. Cover trash cans and sandboxes tightly. Don’t leave pet food unattended; raccoons love cat food. Remember, your dog can carry this infection home to you if you let down your guard. Dogs routinely seek out the raccoon and its droppings for entertainment purposes and may forget to obtain your permission before doing so. Of course, the indiscreet behavior of dogs is exactly why we recommend year-round parasite control, easiest to achieve using a standard heartworm preventative every thirty days, twelve times a year. And always, but particularly after working outdoors or handling your pet, always wash your hands thoroughly before eating or drinking.

Dr M.S. Regan