· Parasitic gastroenteritis (PGE) continues to be a welfare problem in cattle and sheep, causing ill thrift, loss of production and death, and the disease’s epidemiology continues to evolve in response to changes in climate, animal management and husbandry, and other factors, including drug usage. · The regular use of any chemical to control infective organisms poses the risk of development of resistant populations and a subsequent threat to animal welfare. Resistant nematodes in sheep and goats have been reported and are widespread throughout the main sheep-rearing areas of the world. Anthelmintic resistance in Europe has been slower to develop for a number of reasons, but the threat of loss of effective drugs remains. To counter the development of resistance, control measures have been devised and recommended. However, effective control relies on effective surveillance, using appropriate and sensitive monitoring methods.· Recent reports of increasing incidence of liver fluke, together with suspected flukicide resistance, are of concern, particularly as the parasite can result in death in sheep, and can be zoonotic.· This project proposes to develop new and improved methods for detecting and monitoring the development of anthelmintic resistance in the field and to link their use with systems designed to limit the development of resistance and to provide more effect means of parasite control.