Small Intestinal Worms of Sheep and Goats

Small intestinal worm is mostly found in the cooler parts of Australia. It is 10–15mm long and is found coiled close along the wall of the small intestine. It is not a major parasite of sheep but is frequently seen in cattle as well as in goats or sheep that co-graze with cattle. The adult female in the small intestine lays eggs that are passed out in the dung. Under ideal environmental conditions, development from egg to L3 (third stage larvae) takes around seven days, but can take as long as five weeks.

Further ecological information on worms and their control:

• Roundworm life cycle
• Grazing management
• Factors contributing to paddock contamination with worms
• Larval survival of barber’s pole worm
• Scour worm larvae on pasture

Location

The small intestine.

Signs

The small intestinal worm does not usually cause disease or any characteristic signs in sheep and goats, but may contribute to the severity of disease in mixed parasite infections and may worsen the effects of the brown stomach worm and black scour worm.

Diagnosis

The only accurate way to diagnose worm infections before productivity losses have occurred is to conduct a WormTest (worm egg count). The results allow you to make the best choice of drench for the situation.

Signs in sheep and goats only occur after significant production loss has already occurred. Also, these signs can occur with other parasites and diseases.

At post mortem examination, numbers of small intestinal worms are usually small and the worms do not cause any specific lesions in the intestinal lining.

Treatment

There are many options to treat for this worm and your choice will depend on:

• the current size of the burden of this worm
• which other worms are also present and in what proportion
• which drenches are effective on your property and the length of protection you are seeking
• the likely worm-risk over the next few months
• the likely level of worm contamination on your pastures
• the class of sheep or goat affected and their susceptibility to worms
• the last drench group/s you used on this (and other) mobs
• the time until these sheep or goats are sold/slaughtered and the withholding period and export slaughter interval of drenches you might use

Your decision can be assisted by using the Drench Decision Guide, a simple tool that considers some of the points above, including your property’s region.

You can also review the pages under the ‘Treat’ tab on this site to find out specific information about drenches, including:

• Choosing and using drenches,
• drench groups and actives and which worms they treat,
• Resistance status of drench groups,
• Withholding periods for worm, lice and fly treatments for sheep

Note: only a few drench types are registered for use in goats.

The negative impact of this worm can also be reduced through browsing and grazing management strategies and by using one of the integrated worm control programs that have been developed for different regions across Australia.

All broad-spectrum drenches are effective against small intestinal worm. No drench resistance has been reported.