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South Australia worms, flies and lice update - July 2017

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides





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

July has seen modest rainfall across the peninsulas, mid-north and Murray Mallee, while the excellent season continues in the south east.

Worm egg counts have also been modest with the only significant counts being in lactating ewes. These counts have been in the drier areas where feed has been scarce in recent months, which inevitably leads to higher worm larvae intake. It highlights the need to monitor worm counts in lambs from marking onwards as restricted ewe feed intake will reduce lactation and correspondingly lead to increased worm larvae pickup in grazing lambs.

Drier seasons can provide good years for doing drench trials as higher egg counts in lambs provides more favourable circumstances for these investigations. Keep this in mind before drenching lambs as drench effectiveness is ideally monitored at least every three years.

Scouring is often a feature of mid-winter, but don’t assume worms cause them.  Worm burdens tend to steadily increase in lambs and kids and can be in the 1000s of eggs per gram (epg) of faeces before scouring will become apparent. Conversely, adults will often scour due to worm challenge without having significant worm burdens. This is due to their immune response to worm larvae intake causing more rapid feed throughput.

Several bacteria (Campylobacter, Yersinia, Salmonella) as well as a protozoan parasite (Coccidia) are recognised as potential causes of scours in lambs and kids and so a correct diagnosis is advised before attempting treatment. Twenty dung samples at random are best to assess the level of worm or coccidial burden while 3–5 scour samples for microscopic examination and bacterial culture is desirable to diagnose the cause of bacterial scours. Ten blood or liver samples to assess trace element status can also be beneficial in late winter spring where ill-thrift is also evident.

Lice populations generally increase steadily over winter and so if sheep are yarded it is also a good opportunity to part the wool at least ten times on twenty sheep to check for their presence. This can be useful forward planning to coincide treatment if necessary with a spring shearing.

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