Liver fluke causes serious disease (fasciolosis) in cattle and sheep, resulting in production and economic losses. Liver flukes use mud snails as an intermediate host, and wait in damp vegetation to be eaten by grazing animals to complete their life cycle. They develop and move to the liver where they inflict major damage, resulting in liver condemnation at slaughter.
A new approach to studying risk factors for liver fluke infection in cattle has been undertaken by scientists in the Scottish Government’s Centre of Expertise on Animal Disease Outbreaks (EPIC, www.epicscotland.org).
Researchers at BioSS (Biomathematics and Statistics Scotland), the James Hutton Institute and Scotland’s Rural College (SRUC) tested whether slaughter house data from cattle livers (in this case from the Dingwall slaughterhouse) could be a robust and cost-effective approach to identifying risk factors for liver fluke infection. Alternative methods include bulk milk antibody tests or faecal egg counts, which are resource intensive and require personnel for field- and lab-work.
Using condemned liver data is also advantageous because they are from known individual animals and, uniquely, due to the Cattle Tracing Scheme, new statistical modelling techniques in this study were able to take into account each animal’s movements over its lifetime. With the aim of characterising the risk of liver fluke across Scotland this study combined liver and movement data from 8000 cattle with climate data (at each location where each animal had been). The study found an increased risk of liver fluke infection in areas with higher rainfall and warmer temperatures, and in older animals, e.g. 15% of livers were condemned from cattle less than a year old, compared to 35% at 30 months old. Older animals have had more time to acquire infection and more time for the parasite to damage the liver.
The risk factors identified in this study are unsurprising, confirming what we know, and this is good as it shows that this new approach (of combining slaughterhouse, animal movement and climate data) is a powerful tool for informing our understanding of liver fluke risk to cattle in Scotland. This study also forms the baseline for future studies to better predict the impact of climate change on liver fluke risk across Scotland.
It is important to note that, although animal age, temperature and rainfall explained some of the risk of liver fluke infection, this study found that over half of the risk was explained by other factors which were not measured, such as on-farm management. These may include access to wet areas (snail habitat), herd size, grazing season length, treatment application etc. It is therefore a good idea to talk to your vet about testing and treatment options as well as quarantine protocols for new/returning animals. If possible, keep livestock away from the wettest areas or house them during higher risk periods. For more information on fluke risk and control, and to identify higher risk periods, livestock managers can check the fluke forecast from NADIS http://www.nadis.org.uk/parasite-forecast.aspx
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