Barber's pole worm in sheep

Page last updated: Wednesday, 21 March 2018 - 11:52am

Barber's pole worm (Haemonchus contortus) is a potentially harmful roundworm parasite of sheep which can cause a disease called haemonchosis. It is mainly found in coastal and high rainfall areas of Western Australia. In some cases large worm burdens can develop very rapidly and cause sheep deaths without warning. Whether specific pre-emptive action for barber's pole worm is needed depends on the risk level.

Life cycle

The worms are up to 2.5 centimetres (cm) long and occur in the abomasum or fourth stomach of sheep and goats. Female worms have a red and white striped appearance, hence the name ‘barber's pole’.

Their life cycle is typical of roundworms of sheep (Figure 1). Adult worms lay eggs which pass out in the faeces of the host. Barber's pole worms are the highest egg producers of all sheep worms. The eggs hatch within a few days and microscopic larvae emerge. They migrate on to the pasture, where they may be ingested with the herbage grazed by sheep. In the sheep’s gut, larvae develop into adult worms in about three weeks.

The lifecycle of the barber's pole worm in sheep includes adult worms laying eggs which pass onto the pasture in dung, before hatching. The infective larvae are then eaten by sheep.
Figure 1 The lifecycle of the barber's pole worm in sheep

Distribution

Climatic conditions determine where barber's pole worms occur and when they are most prevalent during the year. The development of eggs and larvae is limited to areas and seasons where pastures are moist during the warm months of the year. However, the larvae can survive on pasture for some time, particularly during cool conditions and can can occasionally affect sheep at other times of the year.

In WA, barber's pole worm is mainly a problem in the higher rainfall areas from late spring to early summer and from late autumn to winter. Where the annual rainfall decreases sharply as the distance from the coast increases, it is significant only in a narrow coastal strip. Elsewhere, such as on the south coast, it may occur more than 60 kilometres (km) inland (Figure 2).

The major areas are along the south coast from Walpole to Albany, where it may occur up to 60km inland, and further east in a narrower (20km) strip. On the west coast, problems are more sporadic and only occasionally occur more than 20km from the coast, but can occur from north of Geraldton and down to the Margaret River district.

Major barber’s pole worm risk areas are along the south coast from Walpole to Albany, where it may occur up to 60km inland. On the west coast, problems only occasionally occur more than 20km from the coast, but can occur from Geraldton to Margaret River.
Figure 2 Major barber's pole worm risk areas of WA (shaded areas)

In general, haemonchosis (the disease due to barber's pole worm) rarely affects sheep in areas where the rainfall is less than 600 millimetres (mm). However, outbreaks do occur in drier areas such as the central west coastal district if there is substantial rainfall during summer. There are occasionally outbreaks on northern pastoral properties, following successive wet years with prolonged heavy rainfall.

Contact information

Jennifer Cotter
+61 (0)8 9892 8421