Barber’s pole worms (Haemonchus contortus) have been the cause of a lot of goat ill-health, and many goat owners will have suffered losses as a result of this nasty parasite. Adult Haemonchus contortus worms are about 2 to 3 cm long. Their blood-filled intestines spiral from the mouth to the tail end, so the worm can look like a barber’s pole.
Adult Haemonchus worms live in the abomasum, where they mate. The females lay up to 10,000 eggs a day that pass out onto the pasture in faeces. Larvae hatch from the eggs and migrate up the pasture to be ingested by goats as they graze. In the abomasum, the larvae mature and the adults attach themselves to the lining of the stomach to feed on blood.
A heavily infected goat can bleed to death within a few days. Mild wet autumn weather and high stocking rates increase the risk of heavy infestations.
The main signs of infection are weakness and pale membranes. This is because Haemonchus worms live in the true stomach (the abomasum) where they suck blood. When there are many worms this leads to anaemia. There may also be diarrhoea and there may be bottle jaw (a soft swelling) between the mandibles under the jaw. Affected goats will also have lower growth rates and reduced fertility.
A complicating factor in the treatment and control of barber’s pole worm infestations is that the worms may be resistant to some of the most commonly used worm treatments (anthelmintics.
The best control strategies involve three components: Use of effective anthelmintics, Improved herd and pasture management practices and use of pasture species with anthelmintic properties
Anthelmintics are widely used to control worms such as Haemonchus. Some anthelmintics have been officially approved for use in goats and this will be indicated in the instructions for use on the packaging. However, some of the ‘approved’ anthelmintics have become ineffective because Haemonchus has become resistant to them. There are other types of anthelmintic that will be effective but they may not have been officially cleared for use in goats. For these reasons it is important to consult your veterinarian to help you select the appropriate anthelmintic to use, the correct dose to give, the route of administration, duration of effect and possible adverse effects. It’s also very important that you note the withdrawal period – ie the length of time that must elapse before you can use meat or milk from the treated goats.
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