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Queensland worms, flies and lice update - May 2021

QLD WormBoss Worm Control Programs

QLD WormBoss Drench Decision Guides





Brisbane: Maxine Murphy, Veterinary Parasitologist (

Barber's pole will continue to cycle reasonably well under the current conditions of green growth on pastures and milder temperatures, although it could be a bit cold at night for some. Recently hatched larvae will remain viable over winter and into early spring to form the basis of next summer's worm population.

Currently, sheep are likely to be carrying varying levels of infection depending on many factors such as the amount of rainfall over the last few months, the level of drench resistance in worms, the degree of stock crowding onto pastures, and the class of sheep with younger, more susceptible ones carrying more worms than older sheep. 

Remember the 20/80 rule. In any mob or class of sheep, 20% of the individuals will harbour 80% of the worm burden.

At this time of the year, worm build-up is usually not the explosive build-up seen over summer when the intake of larvae is high and continuous. This means the classic sign of bottle jaw, a fluid-like swelling under the jaw indicating severe anaemia that allows fluid to leak from the bloodstream into the tissues, is  less likely to be seen. Instead, the build-up is expected to be slower, but nonetheless significant coming into lambing and weaning.

Stock with medium worm burdens will suffer some degree of anaemia. Early and consistent monitoring of stock with WormTests will identify at-risk mobs before severe blood loss occurs and well before obvious signs of anaemia.

The sweet spot for worm testing to keep track of any worm build-up under current weather conditions is every 5-6 weeks. A developing burden can be missed by monitoring at shorter intervals as immature adults don't lay eggs and the WormTest relies on detecting eggs in dung. Monitoring at intervals longer than six weeks could miss the rise in adult worm numbers.

A good multi-active drench rather than the usual single-active drench should better cope with any drench resistance in worms and give a better kill. Maybe this year, on some properties, using a long-acting product can be justified. Or perhaps keep the long-acting drench on hand in case of further rain in June when typically, in some years, rain has forced sheep to be stranded on higher ground and that’s when barber's pole can get out of hand.

Earmarking paddocks for lambing is one of the tasks to do this month. Ewes should be carrying the lowest possible worm burdens when they lamb. The pre-lambing drench is usually given about two weeks before lambing. Worm egg counts typically increase after lambs are born due to a temporary loss of immunity to worms in the ewes. This suppression of immunity continues into the early weeks of lactation.

If a significant number of worms survived at the last drench due to drench resistance, paddocks could now be relatively wormy or even quite wormy at the start of lambing. Measures to create low-infectivity paddocks include excluding sheep or goats (and alpacas) from paddocks during the preparation period. If this is not the best use of the paddock, where possible, utilise feed by grazing with cattle or horses (not sheep, goats or alpacas); or use the paddock for growing a crop or making hay.


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