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Raccoon Roundworm

What Is Raccoon Roundworm?


Raccoon roundworm is the common large roundworm or ascarid found in the small intestinal tract of raccoons. Adult worms measure six to eight inches in length and about 0.4 inch in width. They are tan-white in color, cylindrical and taper at both ends.

Raccoon roundworm is common in raccoons in the Northeast and Midwest. Forty to sixty percent of raccoon may carry this parasite.

Roundworm causes the potentially life threatening condition "larval migrans" in a variety of species. Human infections are rare, but can be severe if the parasites invade the eye (ocular larva migrans), organs (visceral larva migrans) or the brain (neural larva migrans).

How Is Raccoon Roundworm Transmitted?

Transmission can occur either directly or through an intermediate host. Raccoons, especially young ones, become infected directly by accidental ingesting microscopic roundworm eggs shed in the feces. Intermediate hosts are also infected by ingesting eggs. If the intermediate host is eaten by a raccoon, the raccoon becomes infected.

Transmission to humans occurs when roundworm eggs are accidentally ingested. Roundworm eggs can remain infective for years, and raccoon feces should be avoided.

What Are the Symptoms of Raccoon Roundworm?

Infected raccoons are normal in appearance and behavior, but in intermediate hosts (mice, woodchucks, squirrels, rabbits and birds) the clinical signs of this may resemble those of rabies. The animal may lose its fear of humans and become aggressive. Eventually the animal becomes comatose and dies.

In humans, pathological lesions observed consist of skin irritations and eye and brain tissue damage due to the random migration of the roundworm larvae. The affected individuals may experience nausea, a lethargic feeling, incoordination and loss of eyesight.

What Is the Treatment for Raccoon Roundworm?

There are currently no drugs that can effectively kill the migrating larvae in the body. Laser surgery has been successfully performed to kill larvae present in the retina of the eye but the damage caused by the migrating larvae is irreversible. Treatment with steroids in intermediate hosts is mainly supportive and is designed to decrease the inflammatory reaction.

How Can I Avoid Raccoon Roundworm?

  • Minimizing contact with areas inhabited by raccoons as well as contact with raccoon feces.
  • If cleaning up raccoon feces, be sure to wear a mask and use bleach on any tools used. Keep in mind that burning is the only effective way to kill roundworm eggs.
  • For trappers, practice normal safety precautions such as using surgical gloves and washing your hands and surfaces used for skinning.

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