The Liver fluke parasite (Fasciola Hepatica) is a major cause of chronic wasting in both cattle and sheep in New Zealand. Infection can occur at any time during the year but is most prevalent during the spring and wet summers, with effects seen during the rest of the year.
The immature stages of this parasite require an intermediate host to develop. In New Zealand, the main host is a snail called Lymnaea columella, which inhabits ponds and marshes and even on irrigated pasture. Stock eat the immature parasite from pasture where it can survive for over a year. Once in the animal, the immature fluke migrates through and feed off the liver, before developing into adult fluke in the bile ducts. This causes massive inflammation of the liver, with loss of blood and protein, resulting in production loss through ill-thrift, anaemia and anorexia.
Most white drenches will kill the mature flukes, but the immature flukes will survive and continue causing damage. It is important to use a product the kills immature flukes during the maximum risk period in autumn and early winter e.g. Flukecare oral or Fasinex 10 oral in sheep and Flukecare oral or Nitromec injection in cattle. If treatment is given after temperatures drop consistently below 10C, when the snail becomes inactive, then the effect of the drench will be prolonged. Some properties with high levels of fluke, or in wet years may need to treat at the end of summer as well as in winter. In countries with high levels of fluke and a wet climate, fluke treatment need to be given to all animals four times a year.
Ref; Flukecare & Se technical bulletin, Jan2016
Image description: Liver damage caused by immature fluke migrating through liver tissue and bile ducts.