What to look for
- Weakness, anaemia, weight loss
- Fluid accumulation under the jaw, known as “bottle jaw”
- Severely infected animals are depressed, anaemic and may have diarrhoea
Cause - a liver parasite (Fasciola hepatica)
Adult liver fluke are flat, oval organisms ~ 25mm long, that live in the bile ducts of cattle, sheep, goats and other animals. Liver fluke have a complicated life cycle:
- adult fluke lay eggs that are passed out in cow manure
- tiny larvae hatch out and infect a specific sort of snail
- several life stages occur in the snail and then a tiny organism emerges and forms a cyst on a blade of grass
- the cysts are then eaten by a cow , hatch into larvae and migrate around the body to the liver, where in large numbers they can damage the liver tissue
- larvae reach the bile ducts and grow into adult liver fluke
- damage to the bile ducts of the liver, causes loss of appetite, lower growth rates and reduced milk production
Specific types of snail are critical to the distribution of liver fluke. These snails are found in areas that tend to be permanently damp such as irrigation channels or slow moving streams or springs. The snails can survive periods of drought but do not move very far from these permanently moist areas.
Animals likely to be affected
Young adult cattle are more susceptible, but liver fluke can occur in any age group especially if susceptible cattle are introduced into liver fluke-infested areas.
Risks to people
There is no risk from cattle. People have been infected with liver fluke by eating plants such as water cress from areas where the relevant snails are present.
Confirming the diagnosis
The location of the farm and the access of cattle to areas harbouring the specific types of snails should be considered. Cow manure and bulk milk can be laboratory tested to help determine if liver fluke are present in a herd but these tests are less accurate for individual animals.
- history of liver fluke in the area
- presence of the intermediate host (relevant snail species)
- access of cattle to permanently damp areas
Liver fluke treatments should be chosen on the basis of the age of the affected animals, whether they are lactating and the stage of the disease. If liver fluke occurs on your farm, consult with your vet to devise a suitable liver fluke control program. Some flukicides may have milk withholding periods after treatment or be less effective against fluke larvae. If liver fluke is not causing serious disease in lactating cows it may be best to treat them after drying off. An effective strategy in some areas is to treat dry cows with a drug that is effective against both mature and immature fluke and then use another drug without a milk withholding period during lactation.