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Larva Migrans and Echinococcus Hydatidosis |
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Baylisascaris procyonis
larva migrans |
Baylisascaris procyonis is the common roundworm of raccoons.
It causes a recognized larva migrans of other wild animals that
serve as intermediate hosts (at least 90 species including rodents,
birds, rabbits, foxes, weasels, otters, badgers), usually leading
to neurologic disease, and this parasite has also been identified
as a zoonotic concern for humans.
Young raccoons and humans and other intermediate hosts become
infected by ingesting eggs containing larvae from soils contaminated
with raccoon feces (raccoon "latrine" sites may be an
important site for infection), whereas adult raccoons become infected
by ingesting larvae imbedded in the tissues of intermediate hosts.
- Infection is very common in racoons.
- 51-82% seropositivity among racoons tested in IN, IL and
WI
- 22% of raccoons in urban Atlanta infected
- 16-32% of raccoon latrines in CA contained infective eggs
- Infected raccoons can shed millions of eggs/day. The eggs
embryonate and become infectious about 2-4 weeks later.
- The eggs are extremely resistant in the environment. Disinfection
requires flaming the soil or boiling contaminated materials in
a solution of 1 lb lye/20 gallons of water.
- Dogs can be infected as an aberrant host, similar to humans,
and can shed eggs in their feces. Cats appear to be relatively
resistant to infection.
- CNS disease has been documented in pet rabbits that were
maintained outdoors.
Disease in humans:
- As with traditional VLM, infections in humans are often linked
to pica behavior and, therefore, occur most commonly in children.
- Baylisascaris procyonis larvae have a predilection
for migration through the CNS in people, as in other animals.
- Approximately 5-7% of the larvae invade the brain and, because
of their large size (up to 2mm in length) and the intense inflammatory
response generated, a great deal of tissue destruction occurs.
CNS disease is manifest as encephalitis with both peripheral
and CSF eosinophilia.
- Although there are only 13 documented cases of Baylisascaris
encephalitis in the U.S., these infections are very serious --
5 of 13 were fatal and survivors may have severe long-term neurologic
sequelae. Unfortunately, because the damage can occur before
the onset of clinical signs, treatment is of limited efficacy.
- This parasite has even been suggested to have potential use
as a bioterrorism weapon.
