Liver Fluke becoming an increasing threat to sheep in the UK
Hannah Johnstone (Vet News Farming Editor)
Liver Fluke is a flat worm which has a complex life cycle heavily dependent on prevailing weather systems, with the optimum being moist and warm. Liver Fluke infestation has a number of steps in the cycle, firstly eggs are deposited by both sheep and cattle in faeces, the eggs in the faeces hatch and are then carried on the intermediate host known as the mud snail. The mud snail then deposits fluke cysts onto grass which the livestock consume. Once within the livestock the young fluke hatch in the intestine to then migrate to the liver, the young fluke are now egg laying adults which takeover the bile system. The cycle covers a 6 month period but is very dependent on weather conditions.
Liver fluke affects both sheep and cattle and is mainly seen in western areas of the UK and becoming more common in eastern areas. Over the end of last year liver fluke infestation is increasing in frequency affecting sheep of all ages. The disease has 3 different forms Acute this type is common around August to October; sheep die suddenly from haemorrhage and liver damage. It is the worst type and 10% of sheep are at risk having a massive knock on affect financially. Sub-acute; the sheep become weak; lose their appetite, depressed with rapid loss of body condition as well as poor fleece quality. Chronic; has similar affects as sub-acute seeing severe emaciation which can cause profits to half by reduction of lamb crop and ewe mortality. With the first 2 types; blood samples show raised liver enzymes and chronic liver fluke can be diagnosed by eggs in faecal samples. Liver fluke is treatable though use of triclabendazole and improved nutrition.
Vulnerability of sheep varies; farms with high stock intensity are vulnerable as well as areas prone to flooding. But the key factor affecting vulnerability of sheep in the UK is the weather. At the end of 2012 sheep were ten times more likely to suffer compared to 2011. David Wilson farm vet and spokesman for NADIS (national Animal Disease Information Service) stated “The very wet summer conditions will have resulted in heavy contamination of many pastures with Liver Fluke infective stages during the summer and autumn”. It is these infective stages that are putting livestock at major risks “many infected animals will subsequently suffer from chronic fluke disease, causing ill thrift and poor production if not effectively treated”. As the weather continues to become increasingly moist and wet, the figures of sheep with liver fluke will remain high having potentially a huge burden financially on farmers through not only loss of sheep but the cost of treatment needed.