Fight the Fluke

Summary

Liver fluke is a parasitic flatworm that can cause serious disease and reduce productivity in sheep and cattle. It is associated with damp, low-lying pasture where marsh snails live. Risk tends to increase after mild winters and during warm, wet summers.

Life cycle and effects

• Adult flukes live in the host’s liver and lay eggs that pass out in feces.
• Eggs hatch into larvae called miracidia, which seek out and infect marsh snails.
• The parasite develops and multiplies inside the snail, then emerges as cercariae. These form infectious cysts on grass.
• Grazing animals ingest the cysts. Young flukes emerge, cross the intestinal wall and migrate to the liver, where they cause tissue damage.
• Immature flukes can cause severe or fatal disease, particularly in sheep. Adult flukes in the bile ducts can reduce weight gain, milk production, growth and fertility.
• Deer and rabbits can also carry the parasite and help maintain its life cycle.
• A typical seasonal pattern is eggs in spring, infected snails in summer, cysts eaten in autumn, and disease effects appearing in winter. Actual risk varies by year, farm and pasture, and cases can occur outside this pattern.

Detection and diagnosis

Possible signs in live animals include exhaustion, anemia and swelling beneath the jaw. Sudden deaths should be investigated, and slaughterhouse reports can provide evidence of infection.

Diagnostic methods include:

• Blood or milk antibody tests, which are useful for young animals in their first grazing season.
• Fecal egg tests, which detect adult flukes but may not identify earlier infection.
• Coproantigen testing, which can detect fluke in feces several weeks before eggs appear. Some commercial laboratories offer this test.

Treatment and control

Not all anthelmintic drugs work against liver fluke, and different drugs affect different stages. Triclabendazole is described as effective against all stages, but resistance has increasingly been reported, so it should be used carefully and only when appropriate.

Flukes can reinfect animals after treatment, so retreatment or moving animals to lower-risk pasture may sometimes be needed. A fecal test about three weeks after treatment can help assess drug effectiveness. Treatment choices and timing should be discussed with a veterinarian.

The video outlines a year-round, four-season approach:

• Spring: Treat animals that overwintered indoors or outdoors with an effective flukicide against adult flukes to reduce egg shedding.
• Summer: Reduce snail habitat by improving drainage, fixing leaking water troughs and leveling trampled areas.
• Autumn: Fence off high-risk areas of pasture.
• Winter: Strategically treat animals that need it. Housing animals can provide an opportunity to reduce parasite burdens and prevent reinfection.

Year-round biosecurity is also recommended. Treat new or returning animals effectively and keep them away from potential snail habitats. Use disease history, diagnostic results, slaughterhouse reports and weather information to develop a farm-specific control plan with a veterinarian or animal-health adviser.

The video also mentions ongoing research into diagnostics, vaccines and disease-control strategies.

Researchers and sources featured

• No individual researchers are named.
• Moredun is apparently mentioned in the closing research statement; the subtitle renders the name as “Mortyn.”
• Veterinarians, animal-health consultants and commercial laboratories are mentioned as sources of advice or testing, but no specific people or organizations are identified.