Review of roundworms in free ranging raccoons in British Columbia

Over the period of January 2012 to January 2014, 17 raccoons were submitted to the Animal Health Centre in Abbotsford, BC for necropsy. Nine were juvenile, 5 were adult and three were of undocumented age. The animals were free ranging and had been found either dead, injured or weak and disoriented by members of the public or employees of provincial agencies.  Of the 17 raccoons, 12 carried patent roundworm infections (7/9 juvenile, 3/5 adults and 2/3 of undocumented age).

The raccoon roundworm, Baylisascaris procyonis, is widespread throughout North America and commonly affects free ranging raccoons. In our two year review, 12/17 raccoons (71%) were carrying the parasite. This agrees with other published infection rates, including those previously found in B.C. ( 1 ) This parasite has a fecal oral life cycle. The raccoon ingests infective eggs from the environment which hatch to larvae. The larvae migrate into the intestinal wall and then emerge as adults into the intestine. Adults lay eggs which exit the intestinal tract via the feces and the cycle starts again. However, if an animal other than a raccoon ingests an infective dose, the larvae will likely migrate to areas outside of the intestine and may cause inflammatory disease in organs (visceral larva migrans), the eye (ocular larva migrans) and/or the brain (neural larva migrans). It is reported that 5 to 7 % of cases involve the brain and up to 90 species of animals, both wild and domesticated, have been diagnosed with this disease. (1)

Baylisascaris procyonis is regarded as an emerging zoonotic pathogen of humans. Similar to animals, if an infective dose is ingested by a person, there may be aberrant migration resulting in inflammatory disease in organs, eyes and/or brain. A dose of about 5,000 eggs is considered infective. This sounds like a lot until you consider that the prevalence of infection in raccoons is high (71% in our review), large numbers of worms are present in an infected raccoon and females are capable of producing up to 800,000 eggs per day! Plus, the eggs are hardy and survive for long periods in the environment. Therefore, the chances of significant infection are high if a person is exposed to an area infected with raccoon feces.

Raccoons are common inhabitants of both rural and urban areas and frequent public and private garbage cans, pet food bowls and other sources of food in close association with humans. Recognition of the potential for infection, particularly for young children, is critical for prevention. Security of garbage receptacles and feed sources in both rural and urban areas can minimize visits by raccoons and thereby reduce the environmental load of raccoon feces replete with eggs.  Good hygiene (hand washing, wearing gloves, keeping hands away from the mouth) is especially important when working in an area frequented by raccoons and, of course, toddlers should never play in such areas.  Remember that we always need to be mindful about what we can do to help improve human/wildlife coexistence in our urban areas

Article by Dr. Ann Britton


1. Sorvillo F, Ash LA, Berlin OGW, Yatabe J, Degiorgio C, and Morse SA. Baylisascaris procyonis: An Emerging Helminthic Zoonosis. Emerg Infect Dis. [serial on the Internet]. 2002 Apr [date cited]. Available from

DOI: 10.3201/eid0804.010273

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