Baylisascaris procyonis – Raccoon Parasite
The Common Intestinal Roundworm of Raccoons is Deadly in People
Oct 24, 2008
Raccoons, Procyon lotor, are found throughout most of North America and Central America, and in parts of northern South America. They have been introduced in Germany and Russia and are expanding their range. More plentiful today in urban and suburban environments than in the wild, where there's one raccoon there may be as many as a hundred per square kilometer.
Raccoons Carry Diseases
Raccoons carry serious diseases that can be transmitted to humans. One is raccoon rabies, now present in much of eastern North America. Another is raccoon roundworm, Baylisascaris procyonis. Though human baylisascaris infections are rare, they are increasing - and they are devastating.
How do People Catch Raccoon Roundworm?
Humans are likely to pick up B. procyonis eggs for various reasons:
- Raccoons create "latrines:" where one raccoon defecates, others will deliberately defecate as well. In places, over 80% of raccoons are infected with B. procyonis, each passing millions of microscopic worm eggs daily. There may be billions of infective eggs in a latrine.
- In urban and suburban settings, raccoon latrines are often under decks where toys or gardening tools are stored, on roofs, on wood piles, on the tops of fences, at the bases of trees, in crawl spaces etc. Where raccoons are plentiful, there can be numerous latrines in a small area.
- The eggs are sticky and will stick to hands, tools and other surfaces. They are very hardy - difficult to remove and difficult to kill. Most infections are in young children who put dirty fingers and other objects in their mouths.
Baylisascaris Infection in Humans
In humans and many other non-raccoon animals, raccoon roundworm infection takes a different course than it does in raccoons. (Raccoons have the worms in the intestine). The more eggs ingested, the more serious the disease because of the number of worm larvae.
Larvae, which grow to two millimeters long, wander aggressively through body tissues doing direct physical damage and also causing a damaging inflammatory response. Typically, larvae go to the brain and the eyes. Prompt treatment is essential but the disease is frequently not suspected and victims often die or suffer serious and permanent brain damage.
Symptoms begin two weeks to a month after eggs are swallowed, but may be subtle at first: mild behavioral changes, sluggishness, irritability, and agitation. Symptoms progress to difficulty with movements, developmental regression, blindness, paralysis, seizures, coma and, all too often, death. Even when treatment is started promptly, symptoms may progress and permanent damage is likely.
The best way to deal with raccoon roundworm infection in humans is to prevent it.
Discourage Raccoons
Raccoons are engaging animals with their cute faces, inquisitive natures and dexterous hand-like forepaws. They'll lift the lid off a garbage can or cooler, unzip a hockey bag, or unscrew the cap of a jar of peanut butter. Bold and unafraid of people they are often seen in human landscapes. Many people deliberately feed them and some keep them as pets. Unfortunately, encouraging raccoons in human communities can be very dangerous. Toronto Animal Services offers excellent advice for discouraging raccoons: "Wildlife in the City: Raccoon."
Related Content:
Sources:
Diagnostic Medical Parasitology 3rd ed. Garcia, Lynn S. and David A. Bruckner. Washington: ASM Press, 1997.
Foundations of Parasitology 6th ed. Roberts, Larry S. and John Janovy Jr. Boston: McGraw Hill, 2000.
"Raccoon." Hinterland Who's Who.
"Raccoon Roundworm Infection (Baylisascaris): a Zoonosis of Pediatric and Public Health Concern." Murray, William J. In: Scheld, W. Michael, Barbara E. Murray, and James M. Hughes, eds. Emerging Infections 6. Washington D.C.: ASM Press, 2004.
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