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South Australia worms, flies and lice update - December 2017

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (

Many parts of South Australia received in excess of 20 mm rain in late November/early December, which had mixed blessings. Regardless of location, it has increased the sheep worm and more immediate flystrike risk for the next few weeks.

The predictions of periodic rainfall interspersed with warm to hot spells associated with a weak La Nina appears to be the case so far this summer. This makes predictions of worm risk quite variable and leads to a greater reliance on worm egg count monitoring (with WormTest) to improve risk assessment.

A common risk for many areas will be Haemonchosis or barber’s pole worm infection. This will normally take 3–5 weeks to emerge following significant summer rain and so worm egg counts done in several mobs 4 weeks after 20 plus mm rain can give a good assessment of worm risk.

The unique characteristic of Haemonchus is that it relies on blood sucking for survival and has a capacity for rapid population explosion. In as little as 3 weeks after ingestion of infective larvae, it can be killing sheep of any age due to anaemia. It prefers warm moist conditions and so is renowned for causing stock losses in wet summers—especially in paddocks with soakage areas and sandy soils that retain moisture.

It is worthwhile checking the colour of the conjunctiva or gums of sheep showing lethargy or sudden death without scouring at this time of year. Pale or white gums is almost diagnostic for Haemonchus and indicates urgent action is required. Fortunately, most drench groups are effective against Haemonchus in southern Australia, and some are specific to Haemonchus and have 4–6 weeks benefit. Refer to specific information on the Paraboss website for more detail.

Always consider Haemonchosis where worm egg counts have risen rapidly to exceed 500 eggs per gram during summer, especially following significant rainfall. A refinement to the traditional worm egg count procedure is a relatively new faecal qPCR test that checks for worm DNA in faecal samples allowing the number of Haemonchus and other roundworm species present to be quantified. It costs $75+ but the additional information is worth it. This test is only available through certain laboratories and so contact your animal health advisor for details.

There is always plenty happening on farms at this time of the year and no one needs more distractions. Most people plan to minimise flystrike risk at harvest time, but not many will be thinking about worms. However, given the value of sheep and wool, a few timely worm egg counts now could be money very well spent.

For December 2017 state outlooks, please follow the links below:
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