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South Australia worms, flies and lice update - December 2018

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





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

Weather patterns have been predictably unpredictable in recent weeks with regular cold fronts interspersed with warm to hot weather almost as if worms have had all their prayers answered!!

Rainfall ranging from 20–60 mm on repeated occasions in parts of the state during December have not only disrupted harvest, but set up ideal conditions for Haemonchus (barber’s pole worm) and flystrike. Both could easily catch sheep producers off-guard at a time when treatment products may be hard to come by, i.e. Christmas/New Year. Drenching at this time of year needs to be broad spectrum, but repeated rainfall events may warrant the inclusion of the chemical closantel to provide 4–6 weeks sustained action against Haemonchus. Few “multi-active” drench products include closantel, and so it may need to be ordered in at a time when supplies are limited. In addition, monitoring worm burdens can also be problematic through the holiday period as testing laboratories are often closed.

The unique characteristics of Haemonchus are that it relies on blood sucking for survival and has a capacity for a rapid population explosion. Scouring is not a feature—but lethargy and “bottlejaw” or submandibular oedema are—so closely monitor these signs. In as little as three weeks following 20+ mm rain, Haemonchus 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 (inside the lower eyelid) or gums of sheep showing lethargy or sudden death without scouring at this time of year. Pale or white gums are almost diagnostic for Haemonchus and indicate that urgent action is required. The stress of yarding anaemic sheep can be sufficient to kill them, and so early diagnosis and treatment are critical. Refer to specific information on the ParaBoss website for more detail.

Worm egg count monitoring in recent weeks has indicated relatively low worm burdens in most parts of the state except the fortunate areas that have had a good spring. However, recent rainfall will have changed the risk considerably. Always consider Haemonchus where worm egg counts have risen rapidly to exceed 500 eggs per gram during summer. A larval culture can be useful to determine whether a Haemonchus-specific product is required. However, where counts exceed 500 epg it would be sensible to simply include closantel or levamisole in the treatment, but don’t forget scour worms (which closantel does not treat, and which may be resistant to levamisole).

A refinement to the traditional worm egg count and culture procedure is the 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 takes about 3–4 days to get a result and 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.

The tough year in many parts of southern Australia has significantly reduced the sheep population, further underpinning the market price for sale sheep as well as meat and wool. This also heightens the need to monitor their health closely so that the New Year can bring new prosperity. I wish you all a happy festive season and New Year.

For December 2018 state outlooks, please follow the links below:
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