Raccoon-borne parasite disease rare but serious

Unexplained neurologic symptoms in a young child, especially brain inflammation with vision or hearing problems, may signal a disease called raccoon roundworm encephalitis, an infection expert says.

While this potentially fatal animal-borne disease is rare and will remain so, Dr. William J. Murray of San Jose State University in California told Reuters Health, it is becoming more common due to the explosion in the raccoon population that has occurred in suburban and urban areas of the United States.

"More physicians are becoming aware of it, but it's an infection that causes a lot of physicians to scratch their head," said Murray, who authored an article on the disease with Dr. Kevin R. Kazacos of Purdue University in West Lafayette, Indiana.

The report is published in the journal Clinical Infectious Diseases.

Raccoons throughout the US carry the roundworm Baylisacaris procyonis and shed the parasite's eggs in their feces. The animals defecate in communal areas, called latrines, which can be found in backyards and trees, on roofs, and even in attics.

Exposure to these latrines is the main risk factor for developing raccoon roundworm encephalitis. Others include age younger than four, male sex, eating dirt, and developmental delay.

Once a person ingests the roundworm's eggs, larvae emerge and migrate from the gut throughout the body. "Although they are not (nerve-seeking) per se, their large size, aggressive migration, and stimulation of intense...inflammatory reactions cause extensive damage to nervous (and ocular) tissues," Murray and Kazacos write.

Symptoms can appear within 2 to 4 weeks of infection, they add, and the severity of illness depends on the number of eggs ingested, the degree of larval migration, and the extent of the resulting inflammation and tissue death.

"In its most severe manifestation it really is a devastating illness that does not respond well to treatment, and kids do not get better," Murray said.

Treatment with albendazole, an anti-parasite drug, within 10 days of infection, along with steroids to prevent inflammatory damage, can provide 95 to 100 percent protection against the disease, Murray and Kazacos note. Once clinical symptoms have developed, albendazole can stabilize the disease but will not reverse its course.

A number of blood tests are now available to diagnose infection with the roundworm, including a test offered by Kazacos' laboratory.

The authors recommend treatment with albendazole for any child observed playing in a raccoon latrine, or if exposure to raccoon feces might be suspected for any other reason.

Murray advises doctors to be mindful of the possibility of roundworm infection, and to talk to the parents of young children about the risks of exposure to raccoon feces.