Farmers and Crofters hoping the suffering liver fluke is presently causing their sheep and cattle won't be repeated should take note of future forecasts.
Research from Scotland’s Rural College and collaborators at University of York, predicts unprecedented outbreaks of the parasite over the next 60 years. By combining tried and tested annual disease forecasting techniques with climate change projections the researchers believe that by 2020 serious liver fluke epidemics among cattle and sheep could be the norm across Scotland, with very severe epidemics in Wales by 2050 and much of western England also affected.
With severe losses being reported this year in established fluke areas, as well as some parts of the country not normally threatened, the researchers argue that their findings should be used to help target future resources for disease surveillance and control.
While of no risk to the safety of the human food chain, the small, flat, parasites cause damage the liver of cattle or sheep which lose condition and, sometimes, suddenly die. The life cycle of fluke (Fasciola hepatica) includes time spent in a pond snail (Lymnaea truncatula) where it multiplies. The snail thrives in wet, poorly drained pastures such as many areas have suffered in the last two years. On leaving their snail hosts the fluke larvae swim onto vegetation and form cysts ready to infect sheep or cattle as they graze. Parasite activity also lowers resistance to other diseases.
Experts from Scotland’s Rural College are well used to forecasting the likely level of Fluke risk each new year and recommending to farmers how best to avoid the worst effects through appropriate management and treatments. For this project they used UK climate change models to help predict where and when the conditions favouring the fluke and its host snail are likely to occur far further into the future.
They found that while the overall risk in the UK will rise it will be far greater in areas where rainfall and winter temperatures are predicted to increase, suiting both parasite and host (liver fluke needs temperatures above 10 degrees C to thrive). In simple terms this means the west coast of Britain and western Wales in particular. In addition the milder winters will increase the survival of larvae and extend the problem from a seasonal to an all year round threat.
While the present fluke crises facing Scottish producers and others has followed two wet years the researchers suggest that in future even drought years could be a problem with livestock forced to graze the grass still growing in boggy areas and which is likely to be carrying a heavy burden of fluke cysts.
For those wanting more information then work was published in the open access journal PLoS One. Read the full article "Predicting Impacts of Climate Change on Fasciola hepatica Risk".
Naomi Fox, who carried out the work for her PhD, said:
“When I first published this work in 2011 there was little response, but after what has been suffered recently I think many in the industry will be able to understand better the knock on effects the research suggests. Certainly SRUC colleagues in Scotland are reporting that because of the conditions and despite treatment programmes, animals are being re infected almost as soon as they are cleared. It is wearing them down.”
“Studying my results I was surprised to see that by 2050 Wales will overtake Scotland as being at most risk from serious fluke epidemics”.
Specialists Scotland’s Rural College believe these results are an early warning about new developments of a well understood problem. This should alert the industry and authorities to the potential threat and help with forward planning. While successful treatments exist there is good evidence that flukes are developing resistance to the medicines used to treat them. If these are over used or used at the wrong time in the fluke’s life cycle the situation could be made worse.
Naomi Fox can be reached on Naomi.Fox@sruc.ac.uk, phone 07719 207 031.
Team Leader SRUC Disease Systems Research, Dr Mike Hutchings Mike.Hutchings@sruc.ac.uk, phone 0131 651 9340.
Brian Hosie, Group Manager SAC Consulting Veterinary Services (a Division of SRUC), 0131 535 3140.