Question

The correct sequence of various larvae in liver fluke is
a) Miracidium, Sporocyst, Cercaria, Redia
b) Miracidium, Sporocyst, Redia, Cercaria
c) Sporocyst, Redia, Miracidium, Cercaria
d) Cercaria, Sporocyst, Redia, Miracidium

Answer 1

Liver fluke is the parasites living in the liver of the various mammals which include humans too. They are a group of trematodes that are present in the phylum Platyhelminthes. They can move along the blood flow and cause disease in the organism they are present in.

Complete answer:
The liver fluke disease is caused by the parasite. It affects mostly the grazing animals which include sheep and cows. It is mostly pathogenic as sheep. The life cycle involves two hosts. The adult parasite lays eggs which are released from the faeces of the animals. When the temperature becomes suitable miracidium develops within the eggs and then migrates to the snail which carries them. When they are inside the body of the snail then they develop and grow and then change into the infective stage which is cercariae and are ejected out of the body. These cercariae then migrate to the moist and wet grasses which are eaten by the sheep and cows and are ingested by them. The young flukes migrate from the mouth of the animals to the liver and start causing damage to the cells and tissue of the animal. Their whole life cycle takes about 18-20 weeks to complete and cause infection.

So, the answer is ‘Miracidium, Sporocyst, Redia, Cercaria’.

Note: The infective stage in the liver fluke occurs only when the temperature and environmental conditions are favorable. An adequate amount of moisture is needed by the fluke to reach the infective stage otherwise they die within 24 hours. The infection in the sheep may be acute or chronic depending upon the number of metacercariae ingested by the sheep.