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Victoria worm update - September 2013

Andrew Whale, Livestock Logic, Hamilton (

Spring conditions have definitely arrived in the South West with some warm sunny days which pastures have responded to. The ground has started to dry out after conditions were very wet in late August early September. We now just require the occasional substantial rainfall over the next 6 six weeks to ensure a great spring. I am sure there are plenty of producers looking to refill hay and grain supplies after the tough Autumn that was hard felt by most livestock producers.

Worm egg counts have continued to rise steadily through winter and spring, a reflection of the growing season and conditions suited to the worm lifecycle. We would expect most WEC levels to start to reduce throughout Spring. As larval ingestion in Spring is reduced with increased pasture volume diluting the amount of worm larvae ingested per mouthful of grass. The increased levels of nutrition also play a big role enabling sheep to better combat the worm and reduced worm burdens. That doesn’t mean you can become complacent with young stock and animals that have not been monitored recently.

Table 1: Livestock logic’s average worm egg counts >200 epg for all mobs for the months from June until September.


% counts >200 epg










For anyone that hasn’t done egg counts recently, this should highlight that now more than anytime over the last 4 months is the most likely time that sheep have required drenching. In particular animals less than 14 months of age are of particular concern and we have seen cases of black scour worm killing weaners as well as maiden ewes at lambing when there has been extending lambing periods. In some instances mortalities have occurred within 28 days of an effective drench, hence the need to monitor young sheep every 3 weeks right through spring to ensure egg counts don’t get to levels that significantly affect production or mortality.

The worm alert sent round by Paul Nilon regarding Tasmania and the Black Scour Worm is in line with what we have seen on some properties in South West Victoria, but probably not to the same degree. Last week for example, in a mob of well grown merino weaners, approx. 12 months of age. 20 lambs died and post mortem of one lamb showed severe gut damage (small intestine), total worm count confirmed 20,000 Trichs (Black Scour Worm) and 3,000 Ostertagia (Brown Stomach Worm).

Key Worm Management Tips for October

  • Perform Drench Resistance Test in 2013 drop lambs at weaning
  • Monitor all stock not WEC’d in last 6 weeks
  • Monitor lambs every 3 weeks right through spring

Tricia Veale, Benalla (

In this area of North Eastern Victoria there was 115 mm of rain in August and 46 mm so far for September. The grass has been growing well.

However the last few months of low to moderate rainfall is keeping worm egg counts at moderate levels generally.

Numbers of worm larvae will most probably continue to increase to their annual peak around October.

It was very interesting to see the report of high drench resistance, which has been identified in some of the oldest classes of sheep drench, written by Nicola Bell, in the Weekly Times recently. This was reported by Novartis Animal Health's technical services manager Dr Justin Bailey.

The study found 96 percent prevalence of drench resistance across Australia to the oldest drench classes, benzimidazole and levamisole, while 54 percent prevalence was found to moxidectin.

Recently the first confirmed case of resistance to Zolvix was noted on a goat farm in New Zealand. This drench is not registered for use in goats.

So, for goat owners… goats continue to exhibit moderate to high worm egg counts on many farms. Please be aware that quite a number of drench products are not registered for use in goats. There is great concern as there is evidence that Ostertagia are becoming increasingly resistant to most of the drench groups. As worms can pass between goats and sheep it is very important that goat owners do not escalate this situation by using routine sheep drench doses on their animals.

It is very important to check the instructions before you drench and… give the correct dose by weight.

It is also essential to check the drench resistance status of your sheep and know which drenches are working on your property. Then use a drench rotation programme using effective drenches only. It's important not to drench animals unless it is needed.

Liver Fluke tests indicate that these parasites are still active on many properties.

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