Parasites and Biliary stones

Clonorchiasis ٢٢
Clonorchiasis
Clonorchis sinensis is a small fluke measuring only 10–25 mm long
and 3-5 mm wide. The fluke may live for up to 25 years the biliary tree of
its host. Occasionally the flukes also live in the pancreatic duct and the
gallbladder, where they lay eggs Operculated eggs are passed into the
feces and when reaching fresh water the eggs are ingested by snails. From
the snails cercariae are released and penetrate freshwater fish. Human
infections originate from ingestion of the raw, dried, salted or pickled
flesh or freshwater fish containing encysted metacercariae. The larva is
released in the duodenum from where it enters the common bile duct and
migrates to the second-order bile ducts. Besides humans, dogs, pigs, cats,
and rats serve as disease reservoirs (Ona and Dytoc, 1991).
Epidemiology:
Clonorchis sinensis (the Chinese or Oriental liver fluke) is a small
trematode commonly found in Southeast Asia. This organism can survive
for up to 25 years inside the human biliary system. Hence infected
patients may seek medical attention many years after moving from an
endemic area. The prevalence of Clonorchis infection may reach 50-70%
in some parts of the world where raw fresh water fish is considered, for
example yue-shun in Southern China and sashima and sushi in Japan. The
life cycle requires two intermediate hosts: the first various species of
snails, the second a freshwater fish. This disease is not found in Egypt
because of the lack of a proper snail host (Leung, 1997).
Life cycle:
The definitive hosts of C. sinensis are humans, dogs, hogs, cats,
mink, and rats. The eggs, shed by adult worms, are deposited in the
biliary tree of these mammalian hosts, enter the intestine, and are passed