Disease caused by liver fluke costs the Australian livestock industry millions of dollars per annum. In the beef cattle sector, costs are a result of production losses on farm and in feedlots, downgrading of livers at the abattoir, as well as the costs associated with control measures and treatments. The strategic autumn treatment is the most important in the annual fluke control calendar, read on to find out why.
Liver fluke (Fasciola hepatica) is a trematode, or flatworm, that infects the liver and bile ducts of many mammals including cattle, sheep, horses, pigs, goats, alpacas, as well as kangaroos, wombats and humans. It often goes undiagnosed in cattle because infected animals don’t always show obvious clinical signs. Young cattle are most susceptible to disease and may show signs of failure to thrive, jaundice, anaemia or even death in severe cases.
Liver fluke is widespread in eastern Australia where annual rainfall is upwards of 600 mm, as well as regions with annual rainfall of 400 mm supplemented by regular irrigation1. Ideal fluke habitats include slow moving shallow watercourses, marshes, springs and irrigation. Vegetation in these areas provide ideal conditions for the infective cysts of liver fluke. On most properties, these ‘flukey’ pastures are isolated to certain areas on the farm where they can be managed or even avoided in heavy fluke risk seasons2.
Liver fluke has a two-host indirect lifecycle, meaning it needs cattle for the maturing stages and a specific type of freshwater snail for the intermediate stages, to complete its lifecycle. Cold conditions over winter suppress the development of both the fluke and the snails. Once the mean daily temperature drops below 10°C fluke eggs cease to hatch, larval stages within the snails cease development and the snails stop reproducing. This means contamination of pasture with the infective cysts peaks over the summer months before naturally declining over winter. Therefore, cattle are exposed to large numbers of infective cysts when grazing during summer, causing them to have higher burdens of early immature, immature and adult fluke in autumn.
This seasonal lifecycle has important implications for the timing of control and treatments.