Question

At which stage in the life cycle of Taenia solium, infects the intermediate host?
A. Hexacanth larva
B. Oncosphere
C. Cysticercus larva
D. Miracidium

Answer 1

Hint: T.solium includes tapeworms. Infected humans pass on the infection through their feces. Pigs act as intermediate host and acquire infection by eating and digesting the eggs. These are transferred into the pig's intestine as oncospheres which break through the intestinal walls.

Complete answer:
Taenia solium or pork tapeworm belongs to cyclophyllidean cestode family taeniidae. Tapeworms have definitive human host and intermediate or secondary pig host. It may transmit from human faeces to the pigs. It can contaminate pig’s fodder. The worm comes back to human while eating uncooked pork that contains tapeworm cyst. The tapeworm eggs ingested by pigs develop into larvae, and then into oncospheres and ultimately to the infective tapeworm cyst.
Development of ingested tapeworm cyst into adult worm takes place in human small intestines. When the oncospores released in the intestine of the pigs, the shell dissolves and the hexacanth larva is liberated. Bile salts activate the hexacanth larva. After this it reaches to the muscles and forms encysted bladder worm or cysticercus. It can survive for several years inside the animal. Length of the adult worm usually 5 m. when the T. Gravid become mature from proglottids, it detach from tapeworm and migrate to the anus or passed in the stool.
Thus, the correct answer is option B.

Note: About 1000 to 2000 proglottids are found in T. saginata adults while T. solium have an average of 1000 proglottids. Eggs are released from gravid proglottids. The gravid proglottids are mostly found in the last fifth of the worm and contain 15-20 lateral branches. Symptoms of infection in humans are usually mild or nonexistent. Tapeworms can lead to death as they take nutrition from us and also block the intestine.