FAECAL EGG COUNTS & EFFECTIVE WORM CONTROL

This article is one in a series on techniques and technologies which farmers can use to increase profit through better managing animal health

E-mail contact: Dr Ray Batey

Sheepvet Australia veterinarians are contactable through: frontdesk@austbreed.com.au

The eggs produced by worms inside a sheep are passed out in the dung, and a faecal egg count is a measure of the number per one gram weight of faeces. It may also be possible to determine the type of worm(s), but this usually requires additional laboratory testing.

Are faecal egg counts always an effective measure of worm numbers?

No. Worm egg counts can be difficult to interpret in many classes of sheep.

• Correlation between the number of worms present and egg count, is poor in older sheep.
• Worm egg count results are generally best applied to a flock rather than individuals.
• Worm egg counts can vary throughout the year.
• Most species of worms cannot be distinguished on the appearance of their eggs under a microscope
• Some important parasites such as liver fluke and thin-necked intestinal worm do have characteristic eggs
• Some species of worms produce more eggs per individual worm than others, and therefore, a significant egg count for one species does not necessarily relate to another. This is particularly so for the barbers pole worm (Haemonchus contortus). Some species may also produce eggs intermittently.
• When scouring is due to immature worms (those not yet producing eggs) there may be few or no eggs in the dung, even though there is a significant parasite problem.

It is important to get good professional veterinary advice when considering the application of worm egg count data in your flock.

Why perform group egg counts?

There should always be a clear objective when undertaking worm egg counts. Sheepvet Australia can assist you to develop or refine the objective(s) for your flock.

1. To assist in deciding whether to treat a flock of young sheep (lambs or weaners).
2. To provide information on the presence of residual worms in adult sheep during summer-autumn.
3. To measure the effectiveness of a worm control program.
4. To enable an estimate of the levels of contamination of a paddock.
5. To indicate whether scouring is due to ADULT worms.
6. To determine whether a particular drench is (or has been) effective (10-14 days after drenching).
7. As a preliminary test to determine whether there are sufficient eggs being produced for a drench resistance (or some other) test to be performed.
8. As individual counts for special purposes, such as assisting in the selection of hogget rams for resistance to parasites.

Why is testing such an important part of worm control?

In simple terms, it's about profitability and sustainability.

• Sustainable worm control is critical to maintaining profitability from sheep.
• There is substantial profit to be obtained from an effective worm control program.
• Ineffective parasite management strategies cause significant losses to farmers.
• Monitoring is the only way of knowing that a program is working.
• Correct timing of treatments requires a knowledge of parasite activity in the flock.
• Resistance to chemical control has become widespread in parasites, involving ALL drench groups.
• The choice of the most appropriate chemical determines profitability of individual sheep operations and it is important to get it right. Drench resistance testing is critical to managing worm parasites.

When is the right time to measure faecal egg counts?

The time to monitor egg counts will vary according to:

• type or class of sheep- including age, sex & breed
• production objectives- meat or wool production
• production objectives- lambs sold or breeding replacements kept
• period of rainfall- and whether mainly summer, winter or throughout the year
• whether sheep are grazing irrigated pastures
• grazing management- rotational or set stocking
• stocking rate
• time of lambing
• time of strategic management practices- shearing, crutching & weaning
• seasonality of local worm or fluke parasites
• worm interactions with other diseases including blowfly strike and nutritional deficiencies

We urge you to obtain independent and competent advice on worm parasite control. A veterinarian experienced in sheep medicine can provide this advice,

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Contact Sheepvet Australia to request a copy of the specimen collection and submission protocol which we provide by e-mail, fax or as a website address.

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Telephone 61 8 9642 1311 or from rural Western Australia 1800 651 226