Haemonchus contortus, also called Barber's pole worm because of the red/white striped occurrence of the female, is a roundworm that can infect goats and sheep.
Females may lay over 5,000 eggs a day, which are secreted form the animal via the faeces. After hatching from their eggs, H. contortus larvae molt several times, resulting in a L3 form that is infectious for the animals. They can take up these larvae when eating grass leaves. The L4 larvae, formed after another molt, suck blood in the abomasum of the animal, potentially giving rise to anaemia and oedema, which eventually can lead to death.
The infection, called Haemonchosis, causes large economic losses for farmers around the world, especially for those living in the warmer climates. Antihelmintics are used to combat these, and other, worm infections for a long time, but resistance of the parasites against these chemicals is growing.