Which parasite causes gall bladder carcinoma and is caused by fish eating? (AIIMS Nov 2012)
a. There are very small trematodes that inhabit the intestine of birds and mammals. The infective stage (metacercaria) can be found in a wide variety of fish.
b. These parasites acquired by eating raw marinated or improperly cooked fish are frequently reported from human infections.
c. These trematodes are represented by the following species Heterophyes heterophyes, Paragonimus werstermonia, Metagonimus yokogawai, Clonorchis sinensis, Opisthorchis sps.,etc.
d. The pathology caused by these parasites is similar and the riskcholangio- carcinoma (gall bladder cancer) may be high in chronic cases
Hepatobiliary parasitic infection –
a. These cases are most often seen in the Far East and include Clonorchis sinensis (most prevalent in Japan, Korea, Vietnam) and Opisthorchis viverrini (most prevalent in Thailand, Laos, Malaysia).
b. Clonorchis is acquired when humans eat fresh water fish that harbor the Clonorchis cyst.
c. The cysts develop into flukes (flatworms) in the friendly confines of the human intestine, and ascend from the duodenum (the first part of the intestine) into the common bile duct where they mature.
d. The worms grow to be approximately 1 cm in length, and have a sucker that allows them to attach to the bile duct epithelium.
e. Constant irritation of the biliary tract epithelium leads to epithelial damage, denudation (loss of the epithelial lining) and regeneration with fibrosis (production of collagen, or scar tissue).
f. Carriage of this worm imparts a 25-50-fold risk of developing biliary tract carcinoma.