In Australia, approximately $6 million cattle are at risk of becoming infected with liver fluke. Livestock owners spend an estimated 10 million per year on drenches that kill liver fluke because the parasite can reduce milk production, feed conversion efficiency, weight gain, fertility and compromise animal welfare. Even with drench intervention the production losses associated with liver fluke infection are estimated to be $80 million per year.
Triclabendazole (Fasinex™, Flukazole™) is the primary drench used to control liver fluke as it is the only registered product that kills multiple life stages of the parasite. However, evidence of liver fluke resistance to triclabendazole is emerging in Victorian dairy herds. In Australia Dr Yvette Brockwell, Dr Tim Elliott, Prof Terry Spithill and Ms Jane Kelley have identified 8 cases of resistance to date. Of concern to the researchers and vets involved in the project is that undetected triclabendazole resistance resulted in the death of calves on one property in Victoria. Resistant liver fluke has also been reported in UK, Spain, Netherlands, Peru, Argentina, and Chile.
Liver fluke infection is prevalent in dairy herds grazing irrigated pastures in the Macalister Irrigation District and the Murray dairy region, including the Upper Murray. With the total milk production lost due to liver fluke across the 3 regions already estimated to be about $28 million/year, it is expected that these losses will only increase over time as more cases of resistance are identified in Victoria.
A new approach to liver fluke control in irrigated dairy regions is urgently required.