Brown Stomach Worm

These worms used to be called ‘Osties’ or ‘Osters’, short for Ostertagia. However, the worm was reclassified in the early 1990s, with the genus name changing from Ostertagia to Teladorsagia.

While Ostertagia is a name still commonly used for the corresponding worms in cattle, the sheep and goat worms are now called Teladorsagia.

Graphic kindly supplied by Professor Nick Sangster, Charles Sturt University

Brown stomach worm occurs in most sheep and goat areas of Australia and is a major parasite in winter rainfall districts. It is relatively rare in Queensland. The brown stomach worm of cattle, Ostertagia ostertagi is known to infect Angora goats, but not sheep.

It is a small red-brown worm, 10mm in length that is just visible on the lining of the fourth stomach (abomasum). Adult female worms lay 50–100 eggs per day. Adults can become arrested or inhibited inside the sheep or goat for varying periods. They resume activity when environmental conditions become more favourable.

Further ecological information on worms and their control:

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

Location

The fourth stomach (abomasum).

Signs

Brown stomach worms do not feed on blood, but damage and inflame the lining of the stomach as they mature from larvae to adult worms. Sheep or goats with heavy infections rapidly lose condition, become weak and lethargic, develop profuse diarrhoea (scour), and may collapse or die.

Entwined masses of worms are found on the lining of the stomach, which is thickened and red and is also covered with whitish nodules (1–2 mm in diameter). Lesions on the wall of the fourth stomach (abomasum) give it a ‘Moroccan’ leather appearance. The carcass is emaciated.

Animals with a lower worm burden are unthrifty and daggy.

Mixed infections of brown stomach worm and black scour worm are more lethal than infection with only one of the worms.

Most commonly, brown stomach worm causes production loss in the absence of obvious signs of disease. Affected sheep or goats have reduced appetite and protein loss into the gut, resulting in a drop in weight gains by up to 35%.

In sheep, wool growth and milk production can each be reduced by 20% before signs become apparent.

Image: Nodules in the fourth stomach of a sheep caused by brown stomach worm (Source: Dr R Woodgate, Department of Agriculture Western Australia)

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.

Visual signs of infection only occur after significant production loss has already occurred. Also, these signs can occur with other parasites and diseases.

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
• what 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; and/or the Paraboss Product Search Tool (below):

You can also review the many ‘Treat’ pages located on the banner at the top of this site to find out specific information about drenches, including their drench active, drench group, length of protection, which worms they treat, dose rate, withholding period, export slaughter interval and manufacturer.

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.