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Gastrointestinal worms

A range of gastrointestinal worms are commonly found in cattle, sheep and goats in Australia. The types of gastrointestinal worms present on a property can vary between regions, with some worms more suited to hot, humid conditions in northern Australia and others to cooler conditions in southern Australia.

It is important that producers know which gastrointestinal worms are common in their region.

Conditions when gastrointestinal worm infections are likely to occur

  • High rainfall regions with more than 500-600 mm annual rainfall or on irrigation.
  • High stocking rates or set stock grazing situations.
  • Livestock grazing short pastures.
  • Young animals, especially after weaning (cattle up to 15 months of age should be considered higher risk).
  • Rising 2-3 year-old cows (are at higher risk of developing type 2 ostertagiasis in summer and autumn, especially in association with calving or nutritional stress).
  • Bulls and bull beef production systems (are higher risk because bulls have lower immunity to gastrointestinal parasites).
  • Ewes and does around the time of lambing or kidding.
  • Hot and humid conditions for Barber's pole worm (Barber's pole worm is more common in summer rainfall region, while black scour worm and brown stomach worm larvae are more of a problem in winter rainfall regions).

Identifying and diagnosing gastrointestinal worm infections

Identifying and diagnosing gastrointestinal worm infections is usually based on one or a combination of the following:

  • History of poor performance on pasture, with growth rates less than expected with known pasture availability and quality.
  • Clinical signs, which can include scouring, weight loss, pale gums and membranes around the eyes or bottle jaw, depending on the worm type.
  • An increased tail in the mob.
  • Worm faecal egg counts and larval cultures.
  • In cattle, the serum pepsinogen test on blood samples helps detect type 2 ostertagiasis.
  • Field trials to assess the growth response from drenching can be very useful when unsure of the parasitological and economic benefit of worm control. This is particularly relevant in regions where gastrointestinal parasites are not considered to be economically important.

Preventing gastrointestinal worm infections

An integrated approach is important when preventing gastrointestinal worm infections. An approach that relies solely on drenching is likely to produce only short-term results and will probably be unsustainable in the long-term.

An integrated approach to gastrointestinal worm control should include the following:

  • Sheep and cattle develop greater immunity to worms than goats.
  • Developing a property worm control plan, as part of the farm biosecurity plan.
  • Knowing the types of worm that occur on your farm and the seasons of highest risk.
  • Monitoring the worm status of livestock regularly, especially higher risk stock during high risk seasons.
  • Preventing the introduction of new or resistant worms onto the property by quarantining all incoming stock and treating them with a quarantine drench.
  • Requesting an animal health statement when purchasing stock so you are aware of the disease status level of assurance that is being provided by the stock vendor.
  • Improving nutrition.
  • Grazing management to provide young animals that are most vulnerable to worms with pastures with lowest contamination.
  • Timing of management events, for example winter-spring lambing in southern Australia improves worm control because ewes have better nutrition.
  • Strategic use of drenches. Drench resistance is widespread in all sheep growing regions of Australia and is also common in goats. Producers should know the drench resistance status of the worms on their property. This is achieved through the use of regular (every 2-3 years) drench resistance tests.
  • Incorporating selection ASBVs for low worm egg count and dag score with selection for important production traits.

More information