Heterophyes heterophyes, a minute intestinal fluke.
embryonated eggs each with a fully-developed miracidium, and eggs are
passed in the host's feces
After ingestion by a suitable snail (first intermediate host), the eggs
hatch and release miracidia which penetrate the snailís intestine
Genera Cerithidia and Pironella are important snail hosts
in Asia and the Middle East respectively. The miracidia undergo several
developmental stages in the snail, i.e. sporocysts
Many cercariae are produced from each redia. The cercariae are released
from the snail
encyst as metacercariae in the tissues of a suitable fresh/brackish
water fish (second intermediate host)
The definitive host becomes infected by ingesting undercooked or salted
fish containing metacercariae
After ingestion, the metacercariae excyst, attach to the mucosa of the
mature into adults (measuring 1.0 to 1.7 mm by 0.3 to 0.4 mm)
In addition to humans, various fish-eating mammals (e.g., cats and dogs)
and birds can be infected by Heterophyes heterophyes
the Middle East, and Far East.
The main symptoms
are diarrhea and colicky abdominal pain. Migration of the eggs to the
heart, resulting in potentially fatal myocardial and valvular damage,
has been reported from the Philippines. Migration to other organs
(e.g., brain) has also been reported.
The diagnosis is
based on the microscopic identification of eggs in the stool. However,
the eggs are indistinguishable from those of Metagonimus yokogawai
and resemble those of Clonorchis and Opisthorchis.
the drug of choice.
* This drug is
approved by the FDA, but considered investigational for this purpose.