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For all districts

Control of liver fluke

UPDATED NOVEMBER 1985

By Dr Ken Coghill, veterinary officer

Liver fluke causes loss of production and sometimes death in sheep and cattle throughout Victoria, except in areas that are too dry or are otherwise unsuitable for the snail which passes them on to the stock.

Life-cycle of liver fluke



Sheep

Acute fluke disease causes sudden weakness and death. It occurs when stock swallow very large numbers of fluke cysts (see diagram).

Chronic fluke disease is the most common form. Animals lose condition, produce poorly, and "bottle-jaw" is commonly seen. Some sheep may die.

Black disease may be precipitated by immature flukes that damage the liver; this causes sudden death.

Control of liver fluke

Control is often very hard and eradication is almost impossible because it is usually not practical to prevent reinfestation of pastures and animals.

Three basic methods of control are used and each must be adapted to the individual farm. They come under the headings of treatment, management, and control of snails.


Cattle

The acute form is similar to that in sheep. The chronic disease in cattle rarely causes death. It may slow growth and reduce milk production, especially in young cattle. Fluke may also precipitate black disease in cattle.


1. Treatment

The use of drenches or injections to kill fluke in the liver of stock is a useful part of a control program but it is not a practical way of eradicating liver fluke, and it will not prevent reinfestation.

The number and type of treatments used must depend on the degree of liver fluke infestation in the area, and on seasonal conditions and the cost of treatment compared to the value of the losses that may be caused.

The recommendations in the table below must be adapted to your property, preferably in consultation with a veterinarian.




Treatment of sheep and cattle to control liver fluke



Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Winter rainfall

Sheep


T


T




T




TT

Cattle




TT




TT





Winter rainfall and summer irrigation

Sheep


TTT


TT


T



T



TT

Cattle




TTT




TT





Year-round rainfall

Sheep


TTT


TT


T


T




TT

Cattle




TTT




TT





TTT: Fluke treatment essential in infected areas.

TT: Fluke treatment usually necessary.

T: Fluke treatment desirable in heavily infected areas.


Which drench?

The traditional drenches such as carbon tetrachloride and hexachlorethane are relatively effective against adult liver fluke but have lower efficiency against immature fluke, and sometimes kill the animal.

2. Management

If your property has some areas free of liver fluke and others which are infective, you can use grazing management in your control of chronic fluke disease.

Stock may be placed on infective pasture (where they will swallow fluke cysts) for up to three months. At three months the fluke will start laying eggs. The stock should then be returned to snail-free areas so that the life-cycle of the liver fluke is not continued. After a further three months, when all the liver fluke will have matured, the stock should be drenched again and returned to the infected area.

Outbreaks of acute fluke disease can still occur when this program is being used.

3. Control of snails.

The snails are about 6mm long and the shell has a clockwise or "right hand" thread. If you can drain swampy areas or convert them into deeper, quickly-moving water, the snails cannot survive, and the life-cycle cannot continue. It is often very difficult and expensive to do this but it may be practicable to fence off areas which are known to harbor snails. Planting of trees in wet areas could also be considered, as the fluke snail doesn't live in areas which have a dense cover of vegetation.

In irrigation areas, the snails breed in the channels, particularly drainage channels, and they can be spread over the pasture during irrigation. This habitat is nearly ideal for the snail but it cannot be changed.

Chemicals available for control of snails are very long-lasting and can kill other forms of life, including fish. Their use cannot be recommended.

Vaccination

Black disease is a bacterial disease which may be precipitated by liver fluke. All stock in liver fluke areas should be vaccinated against black disease.

© 2000 Vic. Dept. Ag.