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Queensland worms, flies and lice update - June 2018

Brisbane: Maxine Murphy, Veterinary Parasitologist (maxine@paraboss.com.au)

Worm control efforts at this time of the year should centre on the pre-lambing ewes. 

  • Will they have a worm-safe paddock with sufficient good quality feed for lambing?
  • Will they have worm burdens that could spell trouble during lactation?
  • Will they need drenching before lambing?

During winter, barber’s pole development slows, especially if pastures are cold and dry. However, black scour worms are more resilient to these conditions and their numbers slowly build—although not usually to extreme levels in south and south east Queensland. An exception is goats in coastal tropical regions during the dry winter season and whose pastures are being irrigated—scour worms can build rapidly in these.

Ewes just prior to lambing temporarily lose some of their immunity to worms and this continues until about 6 weeks after lambing. As a result, worms in lactating ewes and does can produce more eggs than usual. If temperatures on pastures reach at least 18°C and there are heavy dews or rainfall, these worm eggs can hatch into infective larvae that in turn can become a source of infection for the very worm-susceptible lambs/kids-at-foot.

It takes at least 3 months to prepare a safe paddock for lambing/kidding over the winter period. For the majority of sheep or goat regions in Queensland maximum daytime temperatures are mostly about 18°C or above so pasture spelling, grazing with adult cattle, and/or cropping until August/September are your best practice options. In the colder tablelands areas of southern Queensland, the paddock preparation may take up to 6 months—if you are in such an area some of those months will be cold enough to prevent worm eggs hatching. You need to actively prevent contamination (as described above) in the weeks where the maximum daytime temperatures are mostly 18°C or above. (More information).

If you are in a ‘cold zone’ you can happily graze wormy stock on the paddocks ear-marked for lambing for a few weeks when daily maximums are below 18°C as barber’s pole worm eggs won’t hatch at such low temperatures.

If your WormTest results indicate that you have mobs of sheep or goats that need to be drenched, and you intend to use a drench tested to be effective against the worms on your property, then an additional grazing option for you is to graze these animals on the future lambing/kidding paddock, not only while the drench is active, but also for an additional 21 days after the protection (persistence) period of that drench has expired. Why? Because any infective larvae picked up after the expiry of the persistence period will take 21 days to mature and produce eggs back onto grass.

The protection period of a drench is the time the drench is actively killing worms in the host animal. It is about 1–2 days for short-acting drenches, and weeks, or months for persistent products. (This page describes how/when to check the persistence of drenches on your property.)