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. The larval stage can multiply up to 500 times in the snail! Stock ingest the immature parasite from forage, on which it can survive for over one year! Once in the animal, the immature fluke migrates through and feeds 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 that 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 10ºC, 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.
The real prevalence of this parasite in NZ is unknown, although we do know it appears to be increasing. We do have some funding available to look at antibody levels in blood, which is a good indication of exposure. Sheep and cattle do not develop immunity to fluke as they do to worms so treatment of all stock classes, including adults, is vital to limit production losses. If you are worried about liver fluke in cattle or sheep contact your local clinic to discuss with your Vet, the best way to investigate and treat this issue.
Reference: Flukecare and Se Technical Bulletin, January 2016