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Beyond the Bale : June 2019
42 ON FARM STAY VIGILANT OF LIVER FLUKE EVEN IN DRIER TIMES While snail populations that host liver fluke larvae are reduced during extended periods of drought, it’s still important to remain attentive to the prospect of liver fluke infections in your flock. During dry conditions, liver fluke is concentrated where remaining green pasture is located, potentially increasing the infection rate of sheep that gather there. Even as water sources dry out, the snails can survive by sheltering in damp mud beneath ground. Liver fluke (Fasciola hepatica) is a parasite affecting a range of livestock and other species. Millions of sheep and other livestock graze pastures where liver fluke is endemic, mainly in south-eastern Australia. Liver fluke disease – or fascioliasis – is one of the most debilitating parasitic diseases of sheep in Australia. It can cause serious production losses, even in dry times, so it pays to treat and prevent liver fluke if you have it on your property. Production losses for sheep is estimated to be nearly $25 million per year, and $50-$80 million per year in all livestock. Significant losses in sheep and cattle include: • death • reduced quantity and quality of wool • reduced lambing percentages • poor growth rate • increased cost for replacement stock • liver condemnation. Eradication of liver fluke is almost impossible; however, sustainable control can be achieved by the strategic use of drenches combined with grazing management and improved drainage of fluke-infested areas. WHERE DOES LIVER FLUKE OCCUR? Liver fluke is widespread in high rainfall areas (about 600 mm or more) of eastern NSW, Victoria, Tasmania and small areas in Queensland and South Australia - see map opposite. Not all properties in these areas have liver fluke as a suitable habitat for the host snail is also required. Ideal snail habitats are springs, shallow marsh areas, bogs, slow-moving streams, irrigation channels, seepages and low-lying river banks where the land is marshy. WHAT ARE THE SIGNS OF LIVER FLUKE DISEASE? Immature fluke migrate through the liver causing bleeding and tissue damage (scarring), while feeding adult fluke cause blood loss and damage to the bile ducts; these result in anaemia and jaundice. Disease can be acute (sudden onset), sub-acute or chronic (long-term), depending on the size of the infection and how quickly stock become infected; the acute forms often result in death. DO I HAVE LIVER FLUKE ON MY PROPERTY? If you don’t know whether your sheep are infected with liver fluke and you are in a high rainfall area, test those mobs run on paddocks where conditions appear suitable for fluke. Initially test three times a year (January, April and August – when disease or production losses from liver fluke are suspected) for at least two years (ie six tests) using liver fluke egg counts. You can also identify whether a specific paddock is affected by testing mobs only run in that paddock since the last fluke-treatment. Testing options include: • Liver fluke egg counts, using faecal samples, but remember fluke eggs only appear in the faeces of the host 8-10 weeks after infection. • An antibody test (ELISA) using blood samples. • A faecal antigen test from the Charles Sturt University, Wagga Wagga, NSW. HOW AND WHEN DO I TREAT? Any positive fluke egg count means treatment is needed. If testing for two years confirms that sheep are infected at all test times, then ongoing testing can be stopped. In this case, three routine treatments for liver fluke should be given to sheep that have been grazing the affected paddocks in: • April/May • August/September • February. If fluke has been confirmed, but is sporadic, then ongoing monitoring in January, April and August is recommended to determine whether treatment is needed. 1st stage larvae adult flukes in liver eggs via bile duct Cysts Larvae develop and multiply in snail hosts (3-4 months) then form infective cysts on pasture. In suitable conditions larvae hatch and infect snail host. Adult fluke produce eggs in bile duct (8-10 weeks) and pass out in faeces. Immature fluke leave gut and migrate through liver (6-7 weeks) causing damage. Eggs in faeces Host eats fluke larvae on pasture. The Liver Fluke Lifecycle