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Western Australia worm update - December 2013

Nicole Swan, Swan’s Veterinary Services, Esperance (

Harvest is almost finished here. We have had mild weather with some rain but the next week with be hot for us (around 35C).

We have done a number of worm counts this month to date (8 mobs). One mob of weaners had counts up to 3100epg with an average of 1450 epg. These were from a coastal property so most likely Barber's pole.

Most of the ewe mobs tested have had fairly low counts and do not require drenching.

The remaining weaner mobs had average counts between 45 and 225 epg. I have recommended that weaners are drenched with an effective drench onto stubbles. On most farms an effective drench will mean Zolvix or a triple active eg Abamectin /LV/BZ or Moxidectin/LV/BZ.

Have a great Xmas and a safe and happy New Year!

Brown Besier, DAFWA, Albany (

Dry and hot weather has at last come – and it’s what we want for worm control in Western Australia!

After a relatively wormy year and some significant problems in lambs in the last few months, it’s time to ensure sheep are not carrying worms at present, and set the scene for good worm control in 2014.

Weaners and hoggets (2013 and 2012-drops): give summer drenches and run in a crop stubble or a paddock that has dried off.  Paddocks should contain no green plant material before drenches are given, but don’t delay a drench for too long.  Lambs are likely to have worm burdens which may reduce body condition unless removed, but they won’t pick up more worm larvae from dry pastures.

If no dry paddocks will be available before Christmas time, and a drench has not been given for 5- 6 weeks, take a worm egg count to check the urgency for treatment. Alternatively, give a drench and accept that another treatment may be needed once pastures have become as dry as they will (a worm egg count then will indicate).

It is important that summer drenches are as close to 100% effective as possible, as any resistant worms surviving summer drenches are the source generation for the next years’ worm population. We want to keep these to a minimum so they can be diluted by no-resistant worms deliberately allowed to survive in adult sheep.

Adult sheep: Do not drench in summer unless you know these sheep have a significant worm burden – usually it will be well below 200 eggs per gram, and not worth a drench for sheep production reasons. Allowing worms to survive over summer in undrenched sheep means there is some pasture contamination with eggs from less- resistant worms, and once weather conditions allow development to larvae (usually March), they form a valuable population to  mix with resistant worms in summer drenched sheep. The aim is that the resistant worms will be so diluted that they never become a significant part of the total worm population on the farm.

However, it is important that adult sheep don’t carry to many worms into autumn – either drench in early April, or take worm egg counts to see whether this is needed (it usually is).

(See the “Summer-autumn drench” program Farmnote on the DAFWA website, or the WA Regional Worm Control Program on WormBoss.)

Wishing you a very Happy Christmas and 2014!

For December 2013 state outlooks, please follow the links below:
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