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Tips on effective control of liver worms in animals

By Dr Joseph Othieno

Liver flukes have a complex life cycle involving snails. Adult liver flukes lay eggs in the bile ducts of the liver, the eggs are passed out through faeces. Under warm and humid environmental conditions, they hatch into a stage that requires snails for further multiplication.

As the name suggests, this worm attacks the liver. A liver fluke’s life cycle is dependent on water and snails. Liver flukes colonize and destroy the liver tissue of ruminants.

They grow into the next infective stage, patch on grass blades to be fed on by livestock. Once ingested by livestock, they penetrate through the intestines then into the blood and eventually the liver. It is important to understand the basics of this life cycle as the control strategies are derived from it.

Signs of liver fluke

The severity of this condition is determined by the number of parasites ingested. The migration of the flukes widens the bile ducts and causes them to bleed and later calcify therefore impairing the proper functioning of the liver. In sheep, sudden death is common and normally caused by liver failure, internal bleeding and secondary infection with Clostridia bacteria.

Liver fluke infestation results in reduced feed conversion efficiency and subsequently loss of body weight and diarrhea. Due to reduced feed conversion reduction in milk yield is often common.

Anemia is a common feature of liver fluke infestation. Liver flukes increase the susceptibility to other infections due to compromised immunity.

The most characteristic clinical sign is the swelling or accumulation of fluid just below the jaw a condition commonly referred to as bottle jaw especially in sheep. In cattle the fluid or edema tends to occur in the lower abdomen. In slaughter houses liver infested with liver flukes will be condemned.

Prevention

We noted earlier that the control and prevention of the liver fluke is tied to its life cycle. The modification of the environment can help create unconducive conditions that can cut the life cycle of liver flukes. Because the environmental stages and its intermediate hosts (the snail) all require water; draining of stagnant waters is a control and prevention strategy.

Fencing off such areas can also help in creating a barrier between the environmental stages and livestock. Avoid grazing in areas that have stagnant waters.

Biosecurity measures can also be practiced by avoiding introduction into your farm of infected animals. Strict quarantine treating with flukicides and monitoring of new animals should be practiced as a biosecurity measure.

Strategic deworming of the herd in another control strategy. This should be done in animals that graze freely. Deworming is normally done monthly for three months. This helps in reducing the amount of eggs shed through faeces. Preventive or prophylactic administration of flukicides can reduce the occurrence of the disease.

Liver fluke infestation is prevalent during dry seasons when animals are grazed close to stagnant water masses that are infested with snails. The other control strategy is to eliminate the intermediate host – snails. There are chemicals that can kill snails; there is some research on plants that can kill snails but this is yet to be tried out.

Treatment

Fortunately, this condition is treatable using dewormers. Triclabendazoles, Fenbendazoles, nitroxynil, oxyclozanide are effective against liver flukes. Manufacturer’s instructions and veterinary advice should be followed for effectiveness. Effective treatment is based on keen observation of the clinical signs.

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