FieldDxFasciolosisClinical signs, differential diagnosis, treatment and prevention in cattle and sheep.
Overview
A parasitic liver disease of grazing ruminants, acquired from wet pasture carrying an intermediate snail host. Fasciola hepatica (or F. gigantica), a trematode liver fluke with an aquatic snail intermediate host. Zoonotic: this condition can pass to people.
Clinical signs
- Acute disease, 2-6 weeks after ingesting large numbers (usually over 2,000) of metacercariae: distended painful abdomen, anaemia, sudden death — mainly in sheep.
- Chronic disease, from lighter exposure over longer periods: anaemia, unthriftiness, submandibular oedema (‘bottle jaw’), reduced milk yield.
- Even heavily infected cattle may show no clinical signs at all.
Predisposing factors
- Lifecycle needs an intermediate snail host; wet pasture favours the snail population.
- Infection follows ingestion of metacercariae on herbage, which can stay viable on pasture for many months unless they dry out.
- Prepatent period is usually 2-3 months.
Look-alikes to rule out
Treatment
- Triclabendazole is the only anthelmintic with licensed activity against early immature Fasciola hepatica stages, making it the treatment of choice for acute fluke disease.
- For Fascioloides magna, albendazole, clorsulon, triclabendazole, or closantel show partial efficacy, though only albendazole is approved for use in sheep in the US.
Drugs mentioned: Triclabendazole Albendazole Closantel
Prevention
1. Treat infected animals; reduce the intermediate snail population; keep stock off snail-infested wet pasture. 2. Anthelmintic resistance is a recognised problem — see the Closantel, Oxyclozanide, Nitroxynil and Rafoxanide drug entries, and rotate/confirm efficacy rather than assuming any one product still works.
Source
MSD Veterinary Manual — Fasciola hepatica in Ruminants (accessed 2026-08-10)
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER — Fasciolosis (Liver Fluke Disease)
Condensed and attributed, never reproduced whole. Open the full entry in the app.