; Skip to Main Content
Skip Nav Destination

Raccoons are a menace to more than just your garbage can :

December 1, 2016

Editor’s note: This article summarizes key points from two Centers for Disease Control and Prevention (CDC) reports published in Morbidity and Mortality Weekly Report (MMWR). To subscribe to MMWR, visit www.cdc.gov/MMWR.

  • Sircar AD, et al. “Raccoon Roundworm Infection Associated with Central Nervous System Disease and Ocular Disease — Six States, 2013–2015.” MMWR Morb Mortal Wkly Rep. 2016;65(35):930-933,  www.cdc.gov/mmwr/volumes/65/wr/mm6535a2.htm?s_cid=mm6535a2_w.

The roundworm Baylisascaris procyonis is a rare but likely underreported infection that can cause permanent neurologic impairment and death in human hosts.

B. procyonis is found throughout North America, predominantly in raccoons, which typically are asymptomatic. The eggs become infectious weeks to months after entering the environment in raccoon feces. Young children are at particular risk of infection through oral contact with hands, dirt and other environmental objects that can be contaminated with raccoon feces. Once ingested by a human, larval forms of the parasite can migrate to the brain (neural larva migrans), eye (ocular larva migrans) and other visceral organs (visceral larva migrans).

Young children are at particular risk of Baylisascaris procyonis infection through oral contact with hands, dirt and other objects that can be contaminated with raccoon feces. Photo courtesy of Bill Buchanan/U.S. Fish and Wildlife ServiceYoung children are at particular risk of Baylisascaris procyonis infection through oral contact with hands, dirt and other objects that can be contaminated with raccoon feces. Photo courtesy of Bill Buchanan/U.S. Fish and Wildlife Service

The diagnosis of Baylisascaris infection requires a high index of suspicion, including exposure to raccoons and raccoon feces. Serologic testing, which is available through the CDC, detects immunoglobulin G antibodies. Therefore, this test is not able to distinguish between current and prior infection.

The ocular form can be diagnosed by visualization of larvae in the eye. The presence of diffuse deep white matter changes on brain MRI may be suggestive of infection. Additional information about diagnostic testing is available at www.cdc.gov/parasites/baylisascaris.

The MMWR article summarizes seven cases of Baylisascaris infection identified between May 2013 and December 2015 in California, Ohio, Oklahoma, Massachusetts, Minnesota and Virginia. Although only two patients had known contact with raccoons or raccoon pelts, all of them lived in areas where raccoons are common. Four of the cases occurred in children, and the affected people ranged in age from 10 months through 32 years.

Among the six cases of neural larval migrans, presenting symptoms were variable and included altered mental status, confusion, lethargy, headache, impaired sensory and motor function, and seizures. Cerebrospinal fluid (CSF) eosinophilia was a universal finding, and one patient also had peripheral blood eosinophilia. The diagnoses were made based on detection of B. procyonis antibodies in CSF, serum or both.

One child who presented with monocular visual disturbance was diagnosed with ocular larval migrans based on visualization of compatible larva in the eye and a positive serum B. procyonis antibody.

All of the patients were treated with recommended treatment regimens, with all receiving corticosteroids and all but one receiving albendazole. Four patients had persistent neurologic deficits. No deaths occurred.

In addition to raccoons, other species of animals including kinkajous and skunks can transmit Baylisascaris. Avoiding contact with these animals and their excrement is important for preventing transmission.

Dogs uncommonly become infected and can shed Baylisascaris eggs and should be tested regularly and dewormed by a veterinarian. Handwashing after outdoor activities that involve soil contact and advising children against eating soil also are important for prevention. Presumptive treatment with albendazole should be initiated for patients with suspected or confirmed ingestion of raccoon feces.

Raccoons, along with bats, skunks, foxes, coyotes and bobcats, also can transmit rabies. Wild animals should not be kept as pets or approached in their natural habitats.


Which of the following statements about Baylisascaris is false?

A. Baylisascaris is not a nationally notifiable disease.
B. Eggs passed in raccoon feces mature and are infectious if ingested.
C. Larva can migrate to eyes, brain and other organs.
D. Laboratory tests are not commercially available.
E. None of the above.

Answer: E

More information on Baylisascaris and rabies can be found in the AAP Red Book, https://redbook.solutions.aap.org/.

Close Modal

or Create an Account

Close Modal
Close Modal