Zoonotic concern: Baylisascaris procyonis

Date: January 18, 2022; updated February 19, 2022 with reviewer input

By: Christal Pollock, DVM, DABVP (Avian Practice)

Reviewed by: Kevin R. Kazacos, DVM, PhD, DACVM and Sarah Sapp, PhD

Keywords: , , , , ,

Categories: Mammals, 

Key Points

  • Baylisascaris procyonis is commonly known as the raccoon roundworm.
  • This nematode is widespread in raccoons in North America.
  • Adult female worms live in the raccoon intestine, depositing eggs that are shed in feces.
  • Raccoon latrines are communal defecation sites that can concentrate B. procyonis eggs.
  • Baylisascaris procyonis is a zoonotic parasite. Humans as well as a wide variety of other mammals and birds can serve as paratenic or accidental hosts of B. procyonis.
  • When infective eggs are ingested by paratenic hosts, larvae can migrate through internal organs (visceral larva migrans), the brain (neural larva migrans), and eye (ocular larva migrans), causing serious health issues.
  • Dogs are an alternate definitive host as well as a possible paratenic host. Therefore infections in dogs can result in either patent adult worms in the intestinal tract or larval tissue migration.
  • Most human cases have been documented in young children, especially those 2 years and younger, due to a higher risk of ingesting B. procyonis eggs when compared to adults.
  • Individuals with occupational exposure to raccoons or their feces are also at risk for Baylisascaris infection
  • The public health risk of B. procyonis can be reduced by increasing awareness of this pathogen, particularly in individuals and institutions caring for young children as well as animal care workers.
  • Minimize direct exposure to raccoon feces or contaminated materials through avoidance, personal protective equipment, proper cleaning and disinfection, and hand hygiene.
  • Baylisascaris eggs are extremely hardy, but they can be killed using various forms of heat.
  • Raccoon feces can also be physically removed before eggs become infective, making it possible to decontaminate areas and materials.

This zoonotic concern article reviews Baylisascaris procyonis or the raccoon roundworm. Baylisascaris procyonis exhibits a typical ascarid life cycle with adult female worms in the raccoon intestine depositing eggs that are shed in the raccoon feces. Humans can serve as paratenic or accidental hosts of B. procyonis, however more than 150 species of free-ranging and captive wildlife, zoo animals, and domestic animals have also been afflicted. When infective eggs are ingested by paratenic hosts, Baylisascaris larvae can migrate through the brain, eye, and other organs, causing serious health issues. Who is most at risk? What strategies can be implemented . . .

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Further reading

Camp LE, Radke MR, Shihabi DM, et al. Molecular phylogenetics and species-level systematics of Baylisascaris. Int J Parasitol Parasites Wildl. 2018 Oct 22;7(3):450-462. doi: 10.1016/j.ijppaw.2018.09.010. PMID: 30568876; PMCID: PMC6275171.

Fox AS, Kazacos KR, Gould NS, et al. Fatal eosinophilic meningoencephalitis and visceral larva migrans caused by the raccoon ascarid Baylisascaris procyonis. N Engl J Med. 1985;312(25):1619-23. doi: 10.1056/NEJM198506203122507. PMID: 4039793.

Gavin PJ, Kazacos KR, Shulman ST. Baylisascariasis. Clin Microbiol Rev. 2005;18(4):703-18. doi: 10.1128/CMR.18.4.703-718.2005. PMID: 16223954; PMCID: PMC1265913.

Huff DS, Neafie RC, Binder MJ, et al. Case 4. The first fatal Baylisascaris infection in humans: an infant with eosinophilic meningoencephalitis. Pediatr Pathol. 1984;2(3):345-52. doi: 10.3109/15513818409022268. PMID: 6542658.

Kazacos KR. Baylisascaris procyonis and related species. In: Samuels WM, Pybus MJ, Kocans AA (eds). Parasitic Diseases of Wild Mammals, 2nd ed. Ames (IA):Iowa State University Press; 2001. Pp. 301-341.

Moro KK, Abah AE. Epizootiology of zoonotic parasites of dogs in Abua area of Rivers State, Nigeria. Vet Anim Sci. 2018 Dec 11;7:100045. doi: 10.1016/j.vas.2018.100045. PMID: 32734067; PMCID: PMC7386753.

Romeo C, Cafiso A, Fesce E, et al. Lost and found: Helminths infecting invasive raccoons introduced to Italy. Parasitol Int. 2021 Aug;83:102354. doi: 10.1016/j.parint.2021.102354. Epub 2021 Apr 16. PMID: 33872791.

Umhang G, Duchamp C, Boucher JM, et al. Detection of DNA from the zoonotic raccoon roundworm Baylisascaris procyonis in a French wolf. Parasitol Int. 2020 Oct;78:102155. doi: 10.1016/j.parint.2020.102155. Epub 2020 Jun 6. PMID: 32512048.

To cite this page:

Pollock C. Zoonotic concern: Baylisascaris procyonis. January 18, 2022. LafeberVet Web site. Available at https://lafeber.com/vet/zoonotic-concern-baylisascaris-procyonis/