The host of liver fluke are ______?

Step 1: Analyze the question The question asks about the hosts of the liver fluke (Fasciola hepatica). A parasite usually has a primary (definitive) host, where it reaches adulthood and reproduces sexually, and an intermediate host, where the larval stages develop.

Step 2: Recall the life cycle

1. Adult liver flukes live in the bile ducts of the liver of sheep (also cattle and goats). This is the primary host.
2. Eggs pass out of the host in its faeces.
3. In water, each egg hatches into a miracidium larva, which swims and enters a freshwater snail (Lymnaea). The snail is the intermediate host.
4. Inside the snail, the larva develops into a sporocyst, then rediae, then cercariae.
5. Cercariae leave the snail and form metacercariae (cysts) on grass or water plants.
6. Sheep eat the infected grass and become infected again.

Step 3: Match with the options

• A. Pig and snail: pigs are not the usual definitive host of the liver fluke.
• B. Pig and sheep: this leaves out the snail, which is essential.
• C. Sheep and snail: this is the primary host plus the intermediate host, so it is correct.
• D. Pig: incomplete and not the typical host.

Answer: C. sheep and snail

Exam tip: Remember "Sheep = Primary, Snail = Intermediate" for the liver fluke. For the life cycle, use the sequence E-M-S-R-C-M-A: Egg → Miracidium → Sporocyst → Redia → Cercaria → Metacercaria → Adult.