Baylisascaris procyonisBaylisascaris procyonis

Presented by Kayla Schaefer, Tashi Sherpa, and

Julie Sobolewski

TaxonomyTaxonomy

• Kingdom: Animalia• Phylum: Nematoda• Class: Rhabditae• Order: Ascaridida• Genus: Baylisascaris• Species: B. procyonis

HostsHosts

• Definitive Host:– Raccoons (Procyon lotor)

• Reservoir Host:– Dogs

• Paratenic Host:– Rodents– Birds– Lagomorphs– Humans

Geographic DistributionGeographic Distribution

• North America– Infected Raccoons

common in: Middle Atlantic, Midwest, Northeast, California, Georgia

– Human cases found in: California, Oregon, New York, Illinois, Pennsylvania, Michigan, Minnesota

QuestionsQuestions

1. What phylum are we talking about?

Nematoda

2. What kind of a host is a human for this parasite?

Paratenic

MorphologyMorphology

• Unembryonated eggs are thick-shelled and usually oval in shape.  Their size typically is around 80-85 microns by 65-70 microns. 

• Embryonated egg measuring 50 microns in length

MorphologyMorphology

• The adult female worms can grow to be 24 cm long, while the males can grow up to 12 cm long

• Pictured here is an adult female worm on the left and an adult male worm on the right

Life Cycle in Adult RaccoonsLife Cycle in Adult Raccoons

• Adult worms reside within the small intestines of raccoons and shed eggs which are then passed through the feces

• After 30 days the eggs molt into the infective, L2 stage • The embryonated eggs are then ingested by an

accidental host. The eggs hatch and the L2 larvae penetrate the small intestines and migrate throughout the whole body as they continue to grow

• The L2 larvae can then either encyst or continue circulating throughout the body

• An adult raccoon becomes infected when it ingests an infected accidental host

Life Cycle in Juvenile RaccoonsLife Cycle in Juvenile Raccoons

• Adult worms reside within the small intestines of raccoons and shed eggs which are then passed through the feces

• After 30 days the eggs molt into the infective, L2 stage• Juvenile raccoons ingest the embryonated eggs and L2

larvae hatch in the small intestines• The larvae penetrate the intestinal wall, molt to the L5

stage and enter back into the small intestines where they mature to adults

• The adult worms mate and produce the next generation of eggs

Clinical and Pathological SignsClinical and Pathological Signs

• Symptoms of Baylisascariasis generally appear one to three weeks after ingestion, although they may take as long as two months to develop.

• The severity of symptoms depends on the amount of eggs ingested. The infective dose of Baylisascaris is estimated to be 5,000 eggs or less.

• There are usually no clinical or pathological signs in raccoons.

• In heavy infections, intestinal obstructions or a rupture of the intestinal tract may occur, due to the large number of parasites present.

• Parasite may be deadly in accidental host.

Clinical and Pathological SignsClinical and Pathological Signs

Symptoms may include:• Nausea • Lethargy • Liver enlargement • Loss of muscle

control • Coma • Blindness • Death

• Pictured above is a human retina infected with larvae

DiagnosisDiagnosis

• In raccoons:– Examining adult worms– Fecal floatation

• In abnormal hosts:– Examining the larvae – Examining lesions in the brain, eyes, and other tissues that can

be observed by a microscope

• In humans:– Examining the size of the larvae in the skin or eye lesions– In the event of the death of a human, larvae can be detected in

microscopic sections of the brain, heart, lungs, eyes and other affected tissues.

TreatmentTreatment• Raccoons can be successfully

treated with several antihelminthics to kill the adult worms. Effective drugs are: – piperazine, fenbendazole, pyrantel

pamoate, levamisole and organophosphates such as dichlorvos.

• There are currently no drugs that can effectively kill the migrating larvae in humans.

• Laser surgery has been successfully performed to kill larvae present in the retina of the eye, but the damage caused by the migrating larvae is irreversible.

• Treatment with steroids in paratenic hosts is mainly supportive and is designed to decrease the inflammatory reaction.

A female rabbit, suffering from head-tilt, before and after treatment with fenbendazole and

enrofloxacin.

QuestionsQuestions

1. Name two symptoms this parasite may cause.

Nausea, Lethargy, Liver enlargement, Loss of muscle control, Coma, Blindness, Death

2. What drug is effective at killing this parasite in humans?

None

Public Health ConcernsPublic Health Concerns

• Emerging Helminthic Zoonosis– Human

baylisascariasis– Young children– Difficult diagnosis– Low infectious dose– Raccoons proximity to

humans– Egg viability

• Possible Agent of Bioterrorism– Easily acquired– Low infectious dose– Severe/fatal infection– No effective

therapy/vaccine

What to do for ControlWhat to do for Control

• Educate medical community– Awareness concerning

patients with eosinophilic meningoencephalitis, DUSN, and eosinophilic pseudotumor

• Educate public– Awareness of transmission

• Further research

Works CitedWorks Cited• Schmidt, G., & Roberts, L. (2005). Foundations of

parasitology (7th ed.). New York, NY: McGraw-Hill. • http://www.cdc.gov/ncidod/eid/vol8no4/01-0273.htm• http://www.phsource.us/PH/HELM/

helminth_taxo.htm• http://www.dpd.cdc.gov/dpdx/HTML/

Baylisascariasis.htm • http://www.michigan.gov/dnr/0,1607,7-153-

10370_1215012220-27261--,00.html• http://healthlink.mcw.edu/article/954973916.html• http:bio.winona.edu/bates/Parasitology/

Baylisascaris%20procyonis.htm

Questions about ArticleQuestions about Article1. Relatively few human cases have been

reported, what factors suggest that infection is greater than we realize?

Infected raccoons can shed 45,000,000 eggs/day, viability of eggs (months to years), proximity of raccoons to humans

2. From the table reporting human cases, do any seem out of place? Why?

Germany case: note the sex and the age

3. What are some things the public can do to help control this parasite?

Don’t keep raccoons as pets, don’t feed raccoons, protect garbage from raccoon access, discourage exposure to raccoons and their feces