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Queensland worms, flies and lice update - September 2020

QLD WormBoss Worm Control Programs

QLD WormBoss Drench Decision Guides

Sheep

Goats

Sheep

Goats

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

The concept of quarantine for sheep coming onto your property is the same for people returning home from COVID-19 hotspots, but there are differences. While there are currently no accepted treatments for COVID-19, there are some treatments for worms, but knowing which ones to use is not always clear.

Sheep purchased from ‘hotspots’ are likely to be carrying worms resistant to at least some of the currently available treatments. This resistance might not be so much a problem if your property has the same type of drench resistance, but the risk is that purchased sheep may be carrying a more severe form of drench resistance.

Most likely, you will not know the severity of the imported drench resistance until after it has spread across your property. You may be faced with an acute worm infection that is not well controlled by drenches and re-emerges soon after treatment. Even if your vendor drenched the sheep before departure, it would be wise to re-drench on arrival to your property, unless of course your vendor has shared the current test results with you.

The quarantine process for sheep is about killing the worms in the host and managing reinfection from the pastures. 

The quarantine drench, to mitigate the risk of severe drench resistance, should be a combination of no less than four unrelated drench actives, one or two being the newest actives on the market, such as Zolvix or Zolvix Plus and/or Startect. There is no denying that extra work and cost is involved and these should be accepted as part of the overall purchase costs. If you are using multiple drench products, you will have to drench up the race with one product, then up the race again with the next. Read the label to determine if drenches are compatible when mixed. If not compatible, don’t mix!

After drenching, quarantine sheep in yards or a secure paddock for at least three days. During this time worm eggs present in the gut at drenching will pass out with the dung. Sheep can then be released onto a wormy paddock. This is tricky to understand. It’s a numbers game, much like flattening the curve, sheep style. If sheep are moved to a clean paddock, they will drop resistant-eggs from the worms that survived the quarantine drench. These eggs/larvae then form the total worm population on the paddock. If sheep are moved to a contaminated paddock, the numbers of resistant eggs / larvae dropped onto the pasture form only part of the worm population, as these ‘newcomers’ will have to compete with the ‘home’ crowd for hosts. Research has shown that this procedure can slow the development and spread of resistance across a property.

Again, to be thorough, WormTest the imported sheep 10–14 days after drenching.  You are looking for a zero or extremely low (if the pre-drench worm egg count was very high) test result. And finally, keep the quarantine yards free of sheep, goats or alpacas for at least three months in summer or six months in winter to ensure larvae die off and the quarantine paddocks are ready for the next lot of newcomers. 

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