Raccoon Roundworm

Learn how to protect yourself from this parasite.

Humans can contract this parasite through the ingestion or inhalation of the round worm eggs.

Roundworm (Baylisascaris procyonis) is a common intestinal parasite of raccoon and is a cause of a fatal nervous system disease in wild animals. Raccoon roundworm is not new and its occurrence in raccoons ranges from 40-60% in adults and 90-95% in juveniles.

Raccoon roundworm begins when an egg is deposited by an adult worm living in the intestine of an infected raccoon. The microscopic eggs are shed in the feces, and a single defecation may carry anywhere from a few thousand to more than 10 million eggs!

Raccoons tend to defecate in localized areas over a period of time. These "latrines" are located at the base of trees, in barn lofts, woodpiles, attics, chimneys, sandboxes or elevated surfaces such as logs or rocks.

Young raccoons become infected by ingesting eggs that are present in contaminated areas around den sites and adult raccoons become infected by eating intermediate hosts (mice, rats, chipmunks, weasels, woodchucks, squirrels, birds, rabbits) that have the larvae encysted in their tissue.

Roundworm Eggs

The eggs of the raccoon roundworm are some of the most resistant parasites known. The outer covering is sticky and will stick to any type of surface. They are resistant to disinfectants and antiseptics and will continue to contaminate an area for a very long time. Eggs have been known to survive 8-10 years under laboratory conditions and several years in soil during harsh winters. The most effective way to destroy the eggs is through incineration.

Signs and Symptoms

Humans can contract this disease only through the ingestion or inhalation of the roundworm eggs. The presence of raccoons not an imminent threat as far as exposure to this parasite, rather it is the presence of feces and contaminated nesting material.

In humans, the disease is difficult to diagnose. Children are most susceptible to this parasite since they are more apt to place contaminated objects or soil in their mouth. The presence of larvae or the lesions caused by them in the eye are signs most readily seen by a physician. Symptoms may include drowsiness, confusion, loss of muscle coordination or decreased head control. Humans may have permanent nervous disabilities or vision loss and in severe cases, blindness or death may occur.

In suburban areas, raccoons may occur in higher densities. It is important that people make their property less attractive to raccoons by eliminating potential den sites and food sources.

Follow precautions to reduce your risk of exposure and infection
  • Don't keep raccoon as pets-it's against the law in Massachusetts
  • Don’t feed raccoons
  • When sweeping raccoon feces from attics, basements, barns, wear disposable gloves and a protective mask
  • Burn dry feces and contaminated material (hay and straw) if possible
  • Don't use raccoon feces as a garden fertilizer
  • Screen/cap chimneys appropriately, block holes and access to attics, under sheds, porches, decks, and other buildings
  • Secure animal feeds and bedding from being contaminated by raccoon feces
  • Hunters/trappers should wash hands after handling raccoons
  • Use caution with firewood that raccoons may have used as latrines
  • Cover children's sandboxes to keep animals from using them as latrines

To Clean Contaminated Areas -- Washing with bleach will remove the sticky outer covering on the egg but will not destroy the egg. To destroy the egg you must use boiling lye or propane torching.

MassWildlife works to protect the public & wildlife by:
  • Monitoring outbreaks of wildlife disease
  • Sharing information with humane and animal health authorities
  • Prohibiting the importation or relocation of wildlife
  • Prohibiting possession of wildlife as pets
  • Regulating wildlife populations through harvest of animals by licensed hunters and trappers
  • Increasing public awareness of wildlife through education


This information was prepared through the cooperation of: Mass. Department of Fisheries Wildlife and Environmental Law Enforcement and the Northeastern Research Center for Wildlife Diseases, University of Connecticut/Storrs