Common worms in sheep

Meet your enemies! Learn about the important worm species of sheep – effects on the animal, seasonal pattern, diagnosis, treatment and prevention strategies.

Inside the animal 

Sheep worms most often live in the abomasum (4th stomach) and the small intestine. Some worms can exist in both. Sheep almost always carry a mix of worm species.  

diagram of worms in sheep

Where and how bad? 

Most worm species are found throughout New Zealand – with some regional differences. 

For example, Haemonchus (Barber’s Pole worm) is more common in the warmer, northern parts of the country. Whereas Nematodirus mostly only causes problems in the deep South – it’s eggs require winter chilling to hatch and challenge young lambs in spring. 

Barber’s Pole worm and Nematodirus can cause sudden, severe illness and death – though they might not be an issue at your place, depending on location. Trichostrongylus can cause serious disease in autumn throughout NZ if not well managed. The others would typically be part of a mixed worm infection and not a cause of disease on their own. 

Worm species

For information on lungworm and liver fluke, please see: Tapeworm liver fluke and lungworm.

image of Coccidiosis egg and text description