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Heterophyes heterophyes
Heterophyes heterophyes (Von Siebold, 1852) Stiles and Hassal, 1900, is a
common parasite in the lower Nile Valley near the Mediterranean coast. It occurs
in the Orient and has been reported from Western India.
Morphology, Biology and Life Cycle
The mature Heterophyes heterophyes is a minute pyriform worm, broadly rounded
posteriorly and somewhat narrower anteriorly. It measures 1 to 2 mm in length by
0.3 to 0.4 mm in breadth. It is covered with minute spines set close together.
The eggs are small (28 to 30 micron by 15 to 17 microns), have a conspicuous
conical operculum, and each contains a mature miracidium. When these eggs are
ingested by Pirenella conica (Egypt) or Cerithedia cingulata (Japan), they hatch
and proceed with their intra-molluskan stages of development. The cercariae which
escape from the mollusk encyst in fresh or brackish-water fishes to become
infective metacercariae, which constitute the source of infection for man.
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Pathogenicity and Symptomatology
Heterophyes and related species in the mucosal crypts of the duodenum and
jejunum produce superficial irritation, with excess secretion of mucus and
superficial necrosis of the mucosa. In heavy infections this may be accompanied by
colicky pains and a mucus diarrhea. More serious is the occasional deep
penetration of the worms into the mucus coat of the intestine, so that their minute
eggs get into mesenteric venules or lymphatics and are carried to the heart, brain or
spinal cord, where they may stimulate a granulomatous reaction with symptoms
related to these lesions. It has been calculated that 14.6 % of fatal heart cases in the
Philippines result from heterophyid myocarditis.
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Diagnosis
Eggs of H. heterophyes and other heterophyid flukes following their recovery in
the stool must be differentiated from those Clonorchis sinensis and species of
Opisthorchis which are about the same size and general shape.
Treatment
This consists in the administration of
Praziquantel
by mouth as recommended in
F.buski infection.
Epidemiology
Infection is acquired from eating fresh- or brackish water fish in a raw, salted or
dried condition. Brackish-water snails become infected when they ingest the eggs
of the fluke discharged in the definitive host's excreta which reach the water.
Control
Control can be affected by the thorough cooking of all fish intended for human
consumption.