Fascioliasis in dairy cows on irrigated pasture.

The prevalence and severity of fascioliasis was studied in 87 dairy cows from 36 irrigated farms in Victoria. Evidence of Fasciola hepatica infection was found in 85 (98%) cows representing all but one of the herds. The mean fluke burden (7 +/- 6) in cows treated with anthelmintics at drying off was lower (p < 0.05) than in untreated cows (24 +/- 7). Haemoglobin levels in untreated cows (9.6 +/- 0.04) were higher (p < 0.05) than values obtained from treated animals (8.2 +/- 0.3). Severity of bile duct wall thickness and hepatic fibrosis was similar in both groups. None of the measured parameters was affected by the age of the cow. Although fascioliasis was prevalent in these cattle the level of infection was low.