Angiostrongyliasis is infection with
Angiostrongylus cantonensis (cerebral) or
costaricensis (abdominal).
Both are parasites of rats that accidentally infect
humans.
Angiostrongylus
cantonensis (the
rat lungworm) was first
discovered in 1935 by Chen in Rattus rattus, in Canton, China.
Angiostrongylus
cantonensis is the most common cause of eosinophilic meningitis.
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The rodent is the
definitive host while infected mollusks, snails and crabs act as the
intermediate hosts.
Humans are
infected by the 3rd stage larvae, either by eating undercooked
intermediate hosts or by consuming vegetables.
It is a delicate nematode reported in Asia
Pacific region most commonly in South-east Asia and has been reported
from Taiwan, Thailand, Indonesia, Vietnam and Sri Lanka.
The larvae migrate to the gray matter of the brain,
where they molt before ultimately lodging in a pulmonary artery.
After
maturation, the worms lay eggs in the lung that hatch in situ.
Larvae are
coughed up, swallowed, and passed in the faeces.
The life
cycle is completed when larvae infect snails, which in turn are eaten
by humans.
Migrating
infective larvae or young adult worms die in and around blood vessels
and arteries in the brain and provoke an eosinophilic
meningoencephalitis, with a low mortality (less than 1%).
The diagnosis is based on the demonstration of
A. cantonensis in cerebrospinal fluid.
A.
costaricensis, is found exclusively in Central America, infects the
mesenteric veins of rats near the caecum, where it deposits eggs.
After
hatching, larvae migrate to the faecal stream, pass with the faeces,
and infect snails or slugs.
Infective
larvae emerge from the snails or slugs on the slime trail.
Humans become
infected by eating material contaminated with the slime trail.
Worms reach
maturity in the human host and produce viable progeny.
Large nodules
composed of scar tissue, eggs, and larvae cause lower right quadrant
pain.
Surgical
excision of the nodules, together with the appendix, relieves the
symptoms.
Eosinophils in
the cerebral spinal fluid suggest the diagnosis.
Simple analgesia
is sufficient for mild cases. Treatment of those with severe symptoms
remains controversial. Glucocorticoids, lumbar puncture to reduce
intercranial pressure and antihelminthic agents have been used.
Visit:
Visceral Larva Migrans
;
Cutaneous larva
migrans ;
Strongyloidiasis.
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