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Tasmania worms, flies and lice update - January 2021

Tasmania WormBoss Worm Control Programs

Tasmania WormBoss Drench Decision Guides





Perth: Paul Nilon, Nilon Farm Health (

There have been patches of decent rain through most areas, but most perennial pastures are now quite dry. The thing is that the substantial dry pasture residue, and coolness provided by the rain, means the double summer drench program may be a bit compromised, depending on how much contamination has been laid down. Unlike last year’s scorched, decontaminated conditions, contamination being laid down now may well survive a time and be back to bite us in the autumn. Recommendations are:

  • Monitor religiously. It is likely that you will reach the trigger for the second summer drench earlier than some years.
  • You may need a third summer/autumn drench, particularly in young Merinos. The decision is aided by how quickly the lambs’ worm egg counts start to rise after the second summer drench.
  • Areas of the state that frequently get away with a single summer drench will almost certainly need two drenches this year. Graziers in the lower midlands and Derwent Valley take note.


Testing for Fluke: Fluke habitat is expanding, and what were once sporadic habitats may be permanent. Last year’s wet conditions, with some half decent floods in the major rivers, may have compounded the problem. Producers in the chronically infected areas are (generally) aware of the potential for fluke to be an issue, but those in expanding habitat may be blissfully ignorant. Therefore, if you have fluke habitat it’s wise to do some testing, particularly if you have ill-thrifty, non-scouring sheep.

Fluke tend not to get going until about November in Tasmania. Marginal habitat may only be supporting a few infectious stages. Given that, and the fact that the time from pickup to egg laying is some weeks, it’s wise to be cautious about negative fluke tests. Therefore:

  • Start fluke testing now. If the result is negative repeat the test in a month or six weeks.
  • Be aware of black disease: this is a sudden death syndrome triggered by immature fluke migrating through the liver tissue. The story books are full of cases of largescale outbreaks. Most of the cases I’ve seen have been sporadic losses, reflecting the fact most sheep have reasonable 5-in-1 vaccination histories.
  • An alternative to bulk faecal sedimentation test is a blood ELISA test. This has the advantage of being positive as soon as the sheep is exposed to fluke (that is, sooner than a faecal test becomes positive). The disadvantage is that you need to collect bloods!
  • Also keep in mind that Tasmania has at least one case of triclabendazole super-resistant fluke. Do not drench and assume all is well.


The problem with goats is that they do not respect fences, so they can be a biosecurity risk. Footrot and resistant worms may be promulgated by goats. One issue you should not worry about is lice. Biting lice on goats are a different species to those of sheep, and neither host supports or multiplies the other’s lice species.

For January 2021 state outlooks, please follow the links below:
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