CENTRAL NERVOUS SYSTEM (CNS) PARASITES
PHASMIDEA Order: Strongylida

ANGIOSTRONGYLUS CANTONENSIS
 

ang1a-ic

Angiostrongylus cantonensis: the rat lung worm is a nematode
producing human eosinophilic meningoencephalitis.
Human infections have been described
in Asia (Philippines, Indonesia, Malaisia, Thailand, Viet-Nam, Taiwan, Hong-Kong, Japan),
Oceania [Pacific Island (Tahiti, New Caledonia), Papua Nuova Guinea, Australia],
Cuba, Puerto Rico, Hawaii;
in the USA the parasite has been found in rats and molluscs
and one human case has been reported from New Orleans;
in Africa (Madagascar) A.cantonensis has been found in rats.
Section of A.cantonensis young adults within pulmonary blood vessel.
The sections show the reproductive tubes (RT),
lateral chords (LR) and the intestine (I) of the worms.
(Hematoxylin and Eosin, H&E)

ang1b-ic

A.cantonensis: adult worms
(male: 20-22 mm by 320-420 µm, female: 22-34 mm by 340-560 µm)
live in the blood vessels of the lungs of rats where they lay eggs.
Eggs lodge in the terminal branches of the pulmonary arteries
where they hatch liberating first-stage larvae which migrate
to the intestine via the alveolar space, the trachea, the pharynx
and the esophagus; larvae are then eliminated with faeces.
First stage larvae infect the intermediate hosts, molluscs (snails and slugs),
where they develop to the infective third-stage larvae.
Rats become infected by eating infected snails or slugs.
The ingested larvae migrate from rat's intestine to the CNS where they
develop to adults through two stages of development in 2-3 weeks.
Adults then migrate to the subarachnoid space, enter the venous system
and gain the pulmonary arteries where they become mature.
Larvae can be detected in rat's faeces 40-60 days after infection.
Life cycle

ang2-ic

A.cantonensis: several species of terrestrial snails
(Achatina fulica, the Giant African snail), acquatic snails (Pila spp., Viviparus javanica),
or slugs (Veronicella alte and V.siamensis) may act as intermediate hosts
for the development of the larvae to third stage.
The existance of paratenic hosts has been demonstrated:
in freshwater prawns, land crabs and frogs which feed on snails or slugs,
larvae remain infective for a certain period of time and may infect rats,
or humans, when eating the paratenic host.
Achatina fulica (the Giant African snail)

ang3a-ic

A.cantonensis: humans become infected by eating raw
or undercooked snails, slugs, contaminated vegetables or transport hosts;
in man larvae migrate to the CNS, where the development generally stops,
and cause eosinophilic meningoencephalitis.
Section of A.cantonensis in the subarachnoid space with inflammation and hemorrhage.
(Hematoxylin and Eosin, H&E)

ang3b-ic

A.cantonensis: the pathogenesis depends on direct damage caused
by the motile larvae and young adults (7-13 mm in lenght by 100-260 µm),
and on the host's inflammatory granulomatous reaction.
Section of A.cantonensis in the subarachnoid space with inflammation and hemorrhage.
(Hematoxylin and Eosin, H&E)

ang4a-ic

A.cantonensis: histologic examination shows sections
of the worms surrounded by inflammatory cells
(histiocytes, neutrophils and eosinophils), vascular congestion, subdural
and subarachnoid hemorrhage, focal necrosis and hemorrhage in the brain.
Section of young adult of A.cantonensis in the brain without
any inflammatory response: I: intestine, LC, lateral chords.
(Hematoxylin and Eosin, H&E)

ang4b-ic

A.cantonensis: the incubation period ranges from 1 to 5 weeks (average 2 weeks).
Symptoms consist of headache (mainly occipital and temporal),
stiff neck, nausea, vomiting, mild fever, rash, pruritus,
abdominal pain, constitutional symptoms.
Section of young adult of A.cantonensis in the brain, higher magnification:
the intestine (I) and the lateral chords (LC) are well identifiable.
(Hematoxylin and Eosin, H&E)

ang4c-ic

A.cantonensis: meningeal signs, cranial nerves palsies (III, IV, VI, VII),
paresthesias, pain and weakness are the commonest signs.
Death is uncommon.
An ocular form with the presence of young adults of A.cantonensis
in the anterior chamber of the eye has been described with visual loss,
pain, blepharospasm, iridocyclitis and increased ocular tension.
Section of young adult of A.cantonensis in the brain, higher magnification:
the prominent lateral chords (LC) and the cuticle (C) (5 µm) are well identifiable.
(Hematoxylin and Eosin, H&E)

ang9-ic

A.cantonensis: pulmonary involvement is uncommon but rarely
some worms may migrate to the lungs causing severe pneumonia
with massive inflammation, exudation and hemorrhage.
Section of lung during pulmonary involvement by A.cantonensis.
(Hematoxylin and Eosin, H&E)

ang6-ic

A.cantonensis: several adults, male and female may lie within the same pulmonary vessel.
Sections of adults of A.cantonensis within pulmonary vessel:
RT: reproductive tubes; MC: muscular cells; I: intestine.
(Hematoxylin and Eosin, H&E)

ang7-ic

A.cantonensis: no treatment is recognized as effective;
moreover anthelminthics are not recommended.
Section of adult female within pulmonary vessel:
RT: reproductive tubes; MC: muscular cells; I: intestine; LC: lateral chord.
(Hematoxylin and Eosin, H&E)

ang8-ic

A.cantonensis: laboratory diagnosis is based on the observation
of an eosinophilic CSF pleocytosis (500-5.000 cells/mm3, with 20-90% of eosinophils),
with elevated CSF proteins and normal or slightly decreased CSF glucose.
Section of adult female within pulmonary vessel:
RT: reproductive tubes; MC: muscular cells; I: intestine; LC: lateral chord.
(Hematoxylin and Eosin, H&E)

ang10-ic

A.cantonensis: Charcot-Leyden crystals may be observed
in the CSF. Blood leukocytosis with eosinophilia (>10%) is common.
The diagnosis may be confirmed by serological testing (IF or EIA).
Charcot-Leyden crystal. Bright field examination of wet mount preparation.