The most common tapeworm of sheep in Australia is Moniezia expansa. This has the structure of a flat ribbon-like tube of functional units called proglottids with a neck and head at one end.

Find out more about tapeworms of sheep:

• Life cycle
• Location in the sheep
• Effects on the sheep
• Diagnosing tapeworms of sheep
• Treatment

 Life Cycle

Tapeworms have what is known as an indirect lifecycle. Adult tapeworms are found attached, using muscular suckers on their head (or scolex), to the lining of the small intestine.

The head is joined to a neck and proglottids (the functional unit of the tapeworm, also known as segments) grow in a chain structure from the neck.

Each proglottid (segment) is a complete functional unit, including sets of male and female reproductive organs, and thus can fertilise itself or other nearby proglottids as necessary.

Mature proglottids (segments), full of tapeworm eggs, break free from the body of the worm and pass out of the sheep's gut into the environment via the sheep’s dung. They look like grains of rice in the dung. Eggs are released from the proglottids into the environment and can remain potentially infective for several months.

To become infective to sheep the eggs need to first be eaten by a mite that lives in the soil or on pasture (oribatid mite). These mites are more active during the summer months.

To complete the lifecycle mites containing tapeworm eggs are eaten by sheep.

The mites get digested in the sheep's gut and the eggs are released to go on and develop into adult tapeworms in the sheep's gut.

 Location in the sheep

The preferred site of adult tapeworms in the sheep is the small intestine, where it attaches to the inner surface using strong, muscular suckers found on the head of the worm. Mature proglottids (segments) full of eggs break free from the body of the worm and pass out of the sheep's gut into the environment via the sheep's dung.

 Effects of tapeworm on the sheep

There is no definitive and confirmed evidence in scientific literature that tapeworms cause any ill effect to sheep or that removing them gives a beneficial effect.

Folklore blames tapeworms for all manner of problems, but none of it is substantiated.

 Diagnosing tapeworms

Tapeworm segments can be visible in sheep dung with a white rice grain-like appearance. Adult worms, often up to a metre or more in length, can also be seen on post-mortem or, when expelled, as passed in the environment, typically in yards or other areas where sheep are concentrated.

Tapeworm eggs in sheep dung samples can be detected using the standard worm egg count procedure.

 Treatment of tapeworms

It is not possible to justify the treatment of sheep solely for tapeworm as there is no definitive and confirmed research that shows tapeworms have any negative impact on sheep, even very young lambs.

If you feel you must remove tapeworms, use a drench containing praziquantel. Albendazole aids in the removal of tapeworm segments but will not kill the head of the worm.