Common name. Lancet liver fluke
Geographic distribution. Europe, Asia, North Africa, North America and South America
Infection rate. The fluke is primarily a parasite of ruminants, but is occasionally also found in man.
Life cycle. Embryonated eggs passed in the feces are ingested by land snails, in which they undergo a developmental cycle. Cercariae are liberated from the snails during rainy periods and become massed in slime-balls shed on vegetation as the snail crawls. These slime-balls, each of which contains a large number of cercariae, are eaten by ants. In this host, the cercariae become encysted to form metacercariae. For humans to acquire this disease, they must ingest an infected ant.
Morphology. Adult worms are 6-10 mm long and 1.5-2.5 mm wide. The oral sucker is smaller than the ventral one. The testes are slightly lobed and lie almost tandem, immediately posterior to the ventral sucker, with the ovary directly behind them. The brown eggs measure 36-45 ㎛ by 20-30 ㎛ and are operculated and embryonated when laid.
Pathology and clinical symptoms. The flukes penetrate into the fine branches of the bile ducts, in which they lie greatly extended and attached by means of their suckers. The clinical picture in severe cases consists of anemia, edema and emaciation, but many cases show no clinical signs.
Diagnosis. The very small eggs can be detected by direct microscopic stool examination.
Prevention. There is no special preventive measure.
Comments. Differential diagnosis between Eurytrema pancreaticum is needed.
Dicrocoeliid egg from human.
Adult worm of Dicrocoelium dendriticum. Male and female reproductive systems are reversely located compared with other trematodes.
Tai Soon Yong