Floods, above-average rainfall, mild temperatures and the extensive movement of livestock throughout eastern Australia have created ideal conditions for an increase in the prevalence of liver fluke this autumn.
Elanco Australia’s cattle brand manager, Kim Krilich says liver fluke is traditionally considered only to be a problem in high rainfall (>600 mm) or irrigated regions in NSW, Victoria and Tasmania.
“This is because liver fluke requires an environment that allows the intermediate host –freshwater snails – to survive along with the fluke eggs and larval fluke,” she said.
“The prolonged wet conditions and floods means an increase in those areas that support the survival of the snail, fluke eggs and larval fluke – increasing the risk of exposure of grazing livestock to infective stages.
“This, coupled with the widespread movement of cattle and sheep, is heightening the risk of infection rates.
“With a higher risk of introduced livestock being infected with liver fluke, a treatment with an effective flukicide should be considered, particularly if the treatment status is unknown.”
Liver fluke (Fasciola hepatica) is a serious parasite of sheep and cattle that can cause significant economic losses through reduced production, ill health and in some cases, death.
Livestock mainly ingest infective fluke cysts on vegetation over late summer and autumn as they graze near wet areas, such as dam edges and slow-moving streams.
According to NSW DPI’s publication: ‘Liver fluke disease in sheep and cattle’– Boray JC et al (2017) cattle typically graze in fluke habitat at any time, whereas sheep tend to only graze in these wet areas when feed becomes scarce.
If conditions start to dry over autumn, the risk to sheep is likely to increase as they seek green feed in these areas.
Ingested cysts release immature flukes and develop into early immature, late immature and adult fluke over a 10–12 week period, causing serious tissue damage as they migrate through the liver from the intestine to the bile ducts.
This liver damage can significantly decrease growth rates and milk production, while blood loss can cause anaemia and eventually ‘bottle jaw’.
Infected livestock are also susceptible to 'black disease’ and should be vaccinated against Clostridium novyi.
Effective control of liver fluke requires an integrated approach that combines grazing management, strategic treatment and rotation of chemical treatments with different modes of action.
Ms Krilich said flukey areas tend to be confined to certain locations on a farm, so grazing in these areas should be managed to ensure more susceptible livestock – such as young cattle and sheep, have minimal exposure to cysts.
“The timing and selected mode of action of chemical treatment should be based on the likely stage of fluke infection in the animal with the aim to minimise the fluke egg burden on the pasture.
“A flukicide with activity against early immature, late immature and adult stages of liver fluke should be administered in autumn.
“An additional treatment in late winter or early spring treatment using a different mode of action is recommended, particularly if ongoing wet conditions persist.
“A mid-summer drench may also be required in some instances.”
Regular monitoring using carcase feedback or faecal egg count testing are also important to ensure control measures are working.
Elanco has several options to control liver fluke and other parasites, including Fasinex 240, Exifluke 240, Fasimec Cattle and Bomectin F.
“Fasinex 240 and Exifluke 240 are oral formulations that contain triclabendazole and are ideal for use as part of a quarantine drench or the autumn treatment because they are effective against all three stages of triclabendazole-susceptible liver fluke,” Ms Krilich said.
“Fasinex 240 has the additional benefit of being registered for use in sheep, making it suitable for use in mixed livestock enterprises where complete fluke management is required.
“Fasimec Cattle is an oral formulation of triclabendazole and ivermectin, which makes it an option if wider spectrum parasite control is required in cattle.”
Bomectin F is an injectable that controls clorsulon-susceptible adult liver fluke plus a wide range of ivermectin-susceptible internal and external parasites in cattle.
Ms Krilich said Bomectin F may be suitable as a late winter or early spring treatment to target adult fluke and as a rotation from triclabendazole-based treatments.
“With a nil milk withholding period, it is particularly suitable for use in dairy cows.
“Always read and follow the label directions, and ensure good agricultural practices are followed for optimal parasite control.”
