(a) Liver fluke is an internal parasite that affects cattle and sheep in many tropical regions. (i) Name the intermediate host of the liver fluke. [1] (ii) ...

(a)(i) The intermediate host of the liver fluke is the freshwater snail (Lymnaea species). [1]

(a)(ii) The infection cycle proceeds as follows:

1. Adult liver flukes living in the bile ducts of an infected animal produce eggs, which pass out of the host in its faeces. [1]
2. In wet conditions, the eggs hatch into larvae that enter a freshwater snail, where they undergo several developmental stages and multiply. [1]
3. Mature larvae (cercariae) leave the snail and swim to nearby vegetation, where they encyst on grass blades as metacercariae. Cattle become infected when they graze on this contaminated pasture near waterlogged areas and swallow the cysts. [1]

The key point is that infection requires the presence of both the snail host and wet pasture: cattle that never graze near water are at much lower risk.

(b) Two management practices to reduce liver fluke infection risk (any two):

1. Fence off wet, marshy, or waterlogged areas of the farm so that cattle cannot graze near the snail habitats where cysts accumulate on vegetation. [1]
2. Dose the herd regularly with an anthelmintic (flukicide) to kill flukes inside the animals before they produce large numbers of eggs, breaking the parasite's life cycle. [1]

Other acceptable answers: drain swampy areas to reduce snail habitat; rotate grazing to allow pasture contamination to decline.

(c) One observable symptom of heavy liver fluke infection in cattle (any one): weight loss and poor body condition despite adequate feeding; swelling under the jaw ("bottle jaw" caused by fluid accumulation); pale mucous membranes indicating anaemia; diarrhoea; or reduced milk yield. [1]