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Raccoon Roundworm

Raccoon Roundworm

The following presentation is an introduction to raccoon roundworm (Baylisascaris procyonis), a parasite common in North America infecting raccoons, pets, and, rarely, humans.

Raccoon Roundworm © 2022 by E. Nomi is licensed under CC BY-NC-SA 4.0

The University of Nomi

February 06, 2024
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  1. May 2022
    Raccoon Roundworm
    Raccoon Roundworm
    Photo: © Dennis Kunkel Microscopy/science, 2018, on fineartamerica.com

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  2. Roundworms
    • Phylum Nematoda
    • Only have longitudinal muscles1
    – Characteristic thrashing
    movements
    • Digestive tract is single tube1
    • Cuticle made of collagen1
    – Gas exchange and waste
    excretion through gut wall1
    Photos: modified from "Nematode Roundworm" ©Marek Mis/science Photo Library, 2018 on fineartamerica.com; "Typical regions of specialization in a complete digestive system" © Byron Inouye on
    manoa.hawaii.edu/exploringourfluidearth

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  3. Definitive host*:
    Raccoons
    (Procyon lotor)2,3
    Photo: "Raccoon with 4 kits" © Lana Gramlich, 2015 on flickr.com
    *Definitive host =
    Organism in which
    parasite matures to
    adult stage and
    reproduces sexually
    Raccoon Roundworm
    (Baylisascaris procyonis)

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  4. Photos: onlinewebfonts.com, vecteezy.com
    Paranetic host*:
    Wide range of
    vertebrates,
    including humans,
    dogs, rodents, and
    other small
    mammals2
    *Paranetic host =
    A substitute
    intermediate host in
    which no parasite
    development occurs
    until the definitive
    host is reached
    Raccoon Roundworm
    (Baylisascaris procyonis)

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  5. Raccoon Roundworm
    (Baylisascaris procyonis)
    Morphological features2:
    – ♀ adult: 20 to 22 cm
    – ♂ adult: 9 to 11 cm
    Photo: microbewiki.kenyon.edu/images/f/f6/B.Procyonis.size.png

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  6. • Adults live in raccoon intestinal
    tract4
    • Feed on intestinal fluid, tissue,
    blood and mucus4
    Raccoon Roundworm
    (Baylisascaris procyonis)
    Photo: © Iowa State University, Center for Food Security and Public Health, Dr. A. Hamir,
    ARS, USDA on cfsph.iastate.edu/diseaseinfo/disease-images

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  7. Raccoon Roundworm
    (Baylisascaris procyonis)
    Larvae can migrate and
    encyst in tissues5
    – AI = lateral alae
    – EC = excretory column
    – Cu = cuticle
    – In = central intestine
    Photo: Hung, T. et al., 2012, Figure.
    Larva in human brain tissue

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  8. Raccoon Roundworm
    (Baylisascaris procyonis)
    • Adult female worms produce
    115,000–179,000 eggs per day6
    • Eggs passed through faeces in
    raccoon latrines
    – Defecation sites shared by
    several raccoons
    Photo: "Raccoon latrine" by yooperann on flickr.com

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  9. Geographical Distribution
    • Common in raccoons across
    the United States and Canada3
    – Over 80% infected in the
    Northeast, Midwest, and
    West Coast
    • Introduced to Europe, China,
    and Japan through trade of live
    raccoons3 Photo: clipartbest.com

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  10. Direct (monoxenous) Lifecycle
    1.) Eggs in faeces are passed
    into environment.
    – Last up to 5 years7
    Photo: Kazacos, K. R., et al., 2013

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  11. Direct (monoxenous) Lifecycle
    2.) Embryonated eggs
    develop in 2-4 weeks and
    become infective.
    Photo: Kazacos, K. R., et al., 2013

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  12. Direct (monoxenous) Lifecycle
    3.) Raccoon ingests
    embryonated eggs, which
    hatch in intestines.
    Photo: Shafir, S. C. et al., 2011

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  13. Direct (monoxenous) Lifecycle
    4.) Adults sexually reproduce
    in small intestine. Eggs pass
    into environment in faeces.
    – Average of 20,000 eggs
    per gram of faeces6
    Photo: michigan.gov/dnr/managing-resources/wildlife/disease/raccoon-
    roundworm-baylisascaris

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  14. Indirect (heteroxenous) Lifecycle
    3.) Paranetic animal host
    ingests embryonated egg.
    – Includes pet animals, such
    as dogs, cats, and birds8
    Dogs can become definitive
    hosts and pass eggs in faeces

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  15. Indirect (heteroxenous) Lifecycle
    4.) Larvae hatch and migrate
    through somatic tissues to
    encyst in various organs.
    Photo: Kazacos, K. R., et al. 2013

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  16. Indirect (heteroxenous) Lifecycle
    5.) Raccoon can become
    infected by preying on
    infected animals.
    – More common route of
    infection for adult
    raccoons2

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  17. Human Infection
    3.) Paranetic human host
    ingests eggs.
    Photo: atsdr.cdc.gov/sites/lcp/index.html

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  18. Human Infection
    4.) Larvae penetrate gut wall
    and migrate to various
    targets:
    – Visceral organs
    – Central Nervous System
    – Eyes
    Symptoms can develop in 1 to
    4 weeks4.

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  19. Baylisascariasis
    Disease is caused by migration of larvae through various tissues
    (larva migrans) and encapsulation in granulomas2,3,9
    Intestines Liver Lungs Heart
    Tissues
    portal circulation portal circulation pulmonary veins systemic
    circulation
    Photos: istockphoto.com, vecteezy.com

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  20. Baylisascariasis
    Granuloma2,6:
    – Aggregation of connective
    tissue, eosinophils,
    macrophages, and other
    immune cells around larva
    – 1 to 3 mm diameter
    – Larvae become dormant and
    survive for months to years
    Larva encysted in brain of Marmota monax
    Photo: https://www.ncvetp.org/case-of-the-month/archives/09-2018

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  21. Baylisascariasis
    Visceral larva migrans2(VLM):
    – Migration to internal
    organs
    – Larvae leave trail of
    haemorrhage, necrosis,
    and edema
    – Formation of granulomas
    and eosinophilic masses,
    enlargement of organ
    Photo: Weinstein,S.B., 2017, Figure 2
    Granulomas in Rattus rattus lung

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  22. Baylisascariasis
    Neural larva migrans2(NLM):
    – Migration to brain and spinal column
    – Loss of white matter, atrophy, edema, and aggregation of
    lymphocytes and macrophages 4,10
    Photos: Rowley, H. A. et al. 2000, Figure 1

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  23. Baylisascariasis
    Ocular larva migrans
    (OLM)2:
    – Migration through
    retinal arteries to eye
    tissues
    – Inflammation of
    retina, blindness, and
    nerve damage
    Photo: Liu,, G., et al. 2015, Figure 1
    Damage to interior surface of human eye. White arrows
    indicate granulomas.

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  24. Diagnosis
    Clinical symptoms3:
    – Nausea, tiredness, cough, chest pain
    – Impaired attention to surroundings
    – Loss of muscle control
    – Encephalitis, coma
    – Larva observed during eye examination
    – Reported exposure to raccoons
    Ophthalmoscope for eye exam
    Photo: e-mcast.com/shop

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  25. Diagnosis
    Autopsy/Biopsy2,4:
    – Identification of larvae in tissue
    – Identification of eggs in faecal
    flotation
    Serology2,4:
    – Presence of eosinophils in
    cerebrospinal fluid (eosinophilic
    pleocytosis)
    – Detection of larval excretory-
    secretory (ES) antigens in serum
    Eosinophils in dog cerebrospinal fluid
    Photo: © eClinpath, Cornell University College of Veterinary Medicine on eclinpath.com/atlas

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  26. Diagnosis
    Imaging techniques4:
    – Computed tomography (CT)
    – Magnetic resonance imaging (MRI)
    Photos: © Adam Ciesielski on https://www.dovemed.com/common-procedures/radiology-procedures/computed-tomography-ct-head/, indianapublicmedia.org/amomentofscience/mri-machines-
    work/, kuwana-sc.com/brain/113
    CT scan MRI Images Compared

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  27. Treatment
    • Albendazole6
    – Can pass blood-brain barrier
    • Laser photocoagulation6
    – Kills larvae observable in ocular
    tissue
    • Corticosteroids6
    – Adjunctive treatment to
    suppresses inflammation
    NLM is untreatable unless detected early6,7
    Photo: apollopharmacy.in/medicine/albendazole-400mg-tablet

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  28. Prevention is Key
    1.) Clean outdoor contaminated sites6
    – Remove and dispose of faeces
    (wear particulate mask to prevent
    egg inhalation)
    – Use boiling water or flame torch on
    surfaces (eggs killed at > 62 °C
    /144 °F)
    Photo: healthinspectorsnotebook.blogspot.com/2015/05/urban-wildlife-pet-
    diseases-that-can.html

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  29. Prevention is Key
    2.) Regularly deworm pets and monitor
    with faecal egg counts6
    – Cats: mibemycin oxime, ivermectin,
    praziquantel, febantel8
    – Dogs: milbemycin oxime, fenbendazole,
    moxidectin, and pyrantel pamoate11
    Photo: yourpetsource.com/shop/dogs/pyrantel-pamoate-
    suspension-deworming-cats-dogs/

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  30. Prevention is Key
    3.) Limit interactions with
    raccoons3,4,6
    – Do not keep raccoons as pets
    – Keep dogs leashed in parks and
    hiking trails
    – Keep garbage in closed containers
    Photo: briquesduneige.blogspot.com/2011/11/fat-city-no-more-for-raccoons.html
    “DON'T TOUCH ME
    DON'T FEED ME
    I CARRY DISEASES”

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  31. References
    1.) University of Hawai‘i. (2022) Worms: Phyla Platyhelmintes, Nematoda, and Annelida. Retrieved May 10, 2022 from
    https://manoa.hawaii.edu/exploringourfluidearth/biological/invertebrates/worms-phyla-platyhelmintes-nematoda-and-annelida.
    2.) Graeff-Teixeira, C., Morassutti, A. L., & Kazacos, K. R. (2016). Update on Baylisascariasis, a Highly Pathogenic Zoonotic Infection. Clinical microbiology reviews, 29(2), 375–399.
    https://doi.org/10.1128/CMR.00044-15.
    3.) The Centers for Disease Control and Prevention. (2018, April 11). Parasites - Baylisascaris infection. Retrieved May 9, 2022 from https://www.cdc.gov/parasites/baylisascaris/index.html.
    4.) Kazacos, K.R., 2016, Baylisascaris Larva Migrans: U.S. Geological Survey Circular 1412, 122 p., 3 appendixes, http://dx.doi.org/10.3133/cir1412.
    5.) Hung, T., Neafie, R. C., & Mackenzie, I. R. (2012). Baylisascaris procyonis infection in elderly person, British Columbia, Canada. Emerging infectious diseases, 18(2), 341–342.
    https://doi.org/10.3201/eid1802.111046.
    6.) Kazacos, K. R., Jelicks, L. A., & Tanowitz, H. B. (2013). Baylisascaris larva migrans. Handbook of clinical neurology, 114, 251–262.
    7.) Sapp, S., Handali, S., Weinstein, S. B., & Yabsley, M. J. (2018). Detection and Evaluation of Antibody Response to a Baylisascaris-Specific Antigen in Rodent Hosts with the Use of Western
    Blotting and Elisa. The Journal of parasitology, 104(6), 651–659. https://doi.org/10.1645/18-48.
    8.) PetMD Editorial. (2009, March 06). Baylisascariasis in Cats. Retrieved May 26, 2022 from https://www.petmd.com/cat/conditions/infectious-parasitic/c_ct_baylisascariasis.
    9.) Gavin, P. J., Kazacos, K. R., & Shulman, S. T. (2005). Baylisascariasis. Clinical microbiology reviews, 18(4), 703–718. https://doi.org/10.1128/CMR.18.4.703-718.2005.
    10.) Rowley, H. A., Uht, R. M., Kazacos, K. R., Sakanari, J., Wheaton, W. V., Barkovich, A. J., & Bollen, A. W. (2000). Radiologic-pathologic findings in raccoon roundworm (Baylisascaris procyonis)
    encephalitis. AJNR. American journal of neuroradiology, 21(2), 415–420.
    11.) CAPC Vet. (2015, July 01). Baylisascaris procyonis for Dog. Retrieved May 26, 2022 from https://capcvet.org/guidelines/baylisascaris-procyonis.

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