Disease Programs: Common Raccoon Roundworm

The common raccoon roundworm, Baylisascaris procyonis, has been the focus of a collaborative study between the district and Dr. Bill Murray of San Jose State University. We found that a high proportion (36%) of raccoon fecal samples have eggs of these roundworms and an even higher prevalence (60%) for adult worms in dissected raccoons. Baylisascaris procyonis is an intestinal parasite of raccoons that is dangerous to humans who ingest embryonated eggs of the parasite. It can cause severe visceral larval migrans, ocular migrans and CNS migrans as they wander through human tissues. "Millions" of eggs are shed by the adult roundworm in raccoon feces.

The egg has a thickly mammillated outer shell that protects it from most disinfectants. Treatment with bleach removes the outer protein coat, but does not kill them. Large areas of contaminated soil or concrete are best decontaminated by flaming using a portable propane torch. Surface soil can be turned over with a rake or shovel and repeatedly flamed. [Photographs are courtesy of Dr. Bill Murray]

• Update Dec. 2003: A published study can be viewed by clicking here