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Victoria worms, flies and lice update - May 2020

Dr Lexie Leonard
Dr Lexie Leonard

Hamilton: Lexie Leonard, Veterinary Consultant, Livestock Logic (l.leonard@livestocklogic.com.au)

Very adequate rainfall over autumn in the south-west region has seen some amazing pasture growth, with the season looking very favourable for autumn and winter lambing ewes. The rain and sun has also been favourable to worm growth on pastures, and we are still seeing high WEC results come through the lab. 

Sounding like a broken record; monitoring of all stock should be done regularly over winter to ensure production-limiting worm burdens are not missed. Winter is the major time of year we see stock deaths related to poor body condition and low nutrition. Worm control now will help minimise pasture contamination over winter when worm pickup is often increased due to low feed.  While this may not appear to be the case now; very wet, cold pastures have limited growth. 

Ewes should be WEC tested prior to lambing and then again just prior to lamb marking time. Don’t be afraid to spot drench lighter or daggy ewes, or the bottom third of mobs if a bulk WEC comes in low but there appears to be a tail. Often these ewes do better if separated and put in paddocks with less grazing pressure. 

We are seeing higher than usual WEC results in weaner calves, so if you haven’t checked yours recently make sure you do so! All calves should have been drenched at weaning, and should have continual monitoring every 4–6 weeks until the spring flush. Drenches to weaner calves should ideally be with a combination drench; backliners and single action drenches may be more conducive to drench resistance development.  Drench resistance is becoming more common in cattle, and if a complete drench resistance test is too difficult to do, a smaller trial can be done by individually testing 10–20 samples 14 days post drenching to ensure the drench you are using is 100% effective.  WEC is useful in cattle up to 18–24 months old; adult cattle often have intermittent worm egg shedding so false negative results are common.  Blood testing adult cattle can be done to test for stomach worms, but first talk to a veterinarian regarding the necessity and benefit. 

Lice are still rearing their ugly heads around the district. If you are finding lice in your sheep now, a careful control and eradication program needs to be implemented to minimise disruption to your wool and lambs until shearing. Lice issues in lambs can cause significant decrease in growth rates and wool appearance, which can affect the sale of terminal lambs. 


  • WEC results have been varied across regions and mobs
  • ensure you WEC prior to drenching, there’s no point drenching mobs with a WEC of 0 epg!
  • higher than usual WEC results in weaner calves this year.

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