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Queensland worms, flies and lice update - January 2020

QLD WormBoss Worm Control Programs

QLD WormBoss Drench Decision Guides





Brisbane: Maxine Murphy, Veterinary Parasitologist (

The wet season has finally arrived in tropical, coastal and hinterland regions of north Queensland where predominantly goats are reared. For sheep and goats though, the wet season also means barber’s pole infections.  

This roundworm is a prolific egg producer laying up to 10000 eggs per female worm per day and is the worm most likely to cause deaths of stock during hot, wet weather. Most larvae on grass would have died during the ongoing dry conditions in early summer when the relative humidities were well below 60%. Initially, worm burdens may seem to be slow to take off, but in three weeks, the situation could rapidly change as eggs on grass can develop into infective larvae in this time.

Typically, drenches have helped out with the worm problem, but the degree of control achieved through drenches now depends on the level of drench resistance in this worm, and resistance in barber’s pole to drenches is widespread. Careful selection of drenches becomes important and very restricted for goats due to few available registered products. For sheep, the long-acting drenches may be available for sustained controlled of heavy reinfections.

So the thing about barber’s pole during the wet season when pasture coverage is good is that;

  • populations can develop explosively because of high reinfection rates (in turn due to the high egg production rates and high larval survival rates).
  • not only do the adult worms feed on blood, but also do the immatures.
  • the developing immatures are not detected on a WormTest, so repeat testing needs to become a routine.

So how do you interpret a low to moderate WormTest result from stock 4 weeks after a drench? Is it due to continuous reinfection or an inefficient drench? Or both?

A WormTest taken 10 days after the drench can give some clues. If the drench was good, then the WormTest result should be zero (100% kill) eggs per gram OR no more than 2% of the original number of worm eggs present (98% kill). 

So, as prevention is better than cure, try three WormTests between now and April:

WormTest and Drench, if counts are high

WormTest day 10 after the drench—looking for a zero worm egg count to indicate that the drench gave a 100% kill. If this is not the case, then you know what level of worm burden is left in your sheep.

WormTest day 28 after the drench—to determine if another drench if needed.

If a drench was not needed at the first test, WormTest again in 3–4 weeks to pick up any larvae that were present in sheep at the first test, but were undetected by the test.

For January 2020 state outlooks, please follow the links below:
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