Prevalence of Liver Fluke in Victoria
In 2014 and 2016 field surveillance for liver fluke was conducted by researchers at the Department of Economic Development, Jobs, Transport, and Resources (DEDJTR), La Trobe University and private veterinary practitioners. This work was supported by the Victorian Cattle Compensation Fund, a 2014 Science and Innovation Award for Young People in Agriculture, Fisheries and Forestry and The Gardiner Foundation and Dairy Australia. The research was designed to establish the prevalence and economic cost of liver fluke infections in dairy cattle in the three-main irrigated dairy areas of Victoria.
Faecal samples were taken from 20 cows in each herd and the incidence of fluke infection determined using both faecal egg counts and the new coproantigen test which measures fluke antigen in cow faeces. This research found that the average prevalence rates in 83 (1669 cattle) herds across the Macalister irrigation district, the Upper Murray, the Moira shire, the Campaspe Shire and Gannawarra and Loddon shires were 73%, 58%, 39%, 24% and 9%, respectively: these results suggest that significant economic losses are occurring in some herds (Kelley et al, unpublished data).
The lower prevalence in the Goulburn Valley and Gannawarra and Loddon shire may be due to local soil salinity issues. It is known that short-term exposure to saline water increases the mortality of freshwater snails including the intermediate host for liver fluke (Paradise, 2009). We hypothesise that irrigation infrastructure upgrades could also be limiting infection, particularly where the channels have been lined with rock or plastic.
The South west region has not been evaluated due to the known relatively low prevalence of liver fluke in this region (Watt, 1079; Durr et al, 2005). This has been recently confirmed by consultation with local veterinarians and likely relates to the relative absence of irrigation in this region.