Back to Other Articles In This Category

Headaches continue for sheep parasite management


With many sheep producing areas across Australia experiencing ongoing wetter-than-average seasonal conditions, headaches continue in terms of managing worm burdens and blowflies.  

The key points to consider in worm control in a season like this, is that:  

  • worm numbers can increase very rapidly with the ongoing moist conditions, and warm temperatures (for Barbers Pole worm, especially)  

  • pasture rotations may not be as effective as usual because worm larvae may persist for longer than normal (which is why you will be seeing sheep reinfected with worms sooner than usual) 

  • there may be less opportunity to avoid heavily contaminated pastures (see point above and consider your pastures to be “dirty”) 

  • preparing “worm-safe” pastures will be less effective with regular falls of rain and milder temperatures. 

This all leads to potentially more headaches, and most likely more treatments than you would administer in an average season.  

With this in mind, the best tool in the toolbox for managing worms in your sheep flock this year is the WormBoss suite of tools, which includes a WormBoss drench decision guide for your area.  

If you are not regularly conducting worm egg counts, then do yourself and your sheep a favour and start doing it today! It’s a cost-effective way of keeping ahead of the game with worms, and avoiding things getting out of control. Here is a link to how to do this!

There are several pillars of effective worm management in your sheep flock: 

  1. Follow a planned annual program aiming to minimise the exposure of worm-susceptible classes of sheep to heavy worm intake. 

  1. Worm test – conduct regular worm egg counts to keep an eye on what worm levels in your sheep are doing (use a WEC QA approved lab). 

  1. Use effective products (“effective” equates to a 95 per cent or higher reduction in worms) that contains at least TWO effective actives and ensure you use the correct dose rate. 

  1. Follow up drenching with another WEC to check that the product has been effective (at least a couple of times per year). 

  1. Continue to monitor your mobs for increases in WECs, and treat as mobs reach thresholds. 

  1. Know the relative susceptibility of the different classes of livestock on your farm and the types of worms that you normally see (a larval culture will determine this). 

MONITORING is the key point here and careful, attentive monitoring can prevent avoidable adverse events, and help keep your stock thriving.  

What about long-acting drenches? Long-acting drenches may seem like a silver bullet – “treat and forget” scenario, but there can be the downside of an increase in drench resistance.  

The key factors to remember are: 

  1. Limit long-acting products to known high-risk worm situations and especially worm-susceptible sheep classes.

  1. Use a primer (any effective drench) at the same time as the long-acting treatment.

  1. Check worm egg counts over the course of the product pay-out period, and give an effective drench if worm egg counts are over about 100 eggs per gram. A “tail-cutter” (exit drench) may be necessary if counts are this high by the time that the product runs out.  

Failing to manage the use of long-acting products will reduce their worm control benefits. In particular, where larval survival this year is high, resistant worms that are not killed by the long-acting treatment will survive in high numbers to contaminate the pasture right through to next spring.  

Sheep blowflies 

The story is similar for the sheep blowfly season this year in many parts of Australia, unfortunately. Many producers have had to retreat animals as the continued wet conditions has put all preventative products under considerable pressure this summer.  

Key points for managing sheep blowflies this summer are: 

  • Know the protective period of your chosen product. 

  • Apply the product at the correct dose for your animals.  

  • Apply product via the prescribed method. 

  • Monitor all animals throughout the period of protection – don’t just treat them and forget them. 

A lot of this comes back to carefully reading the label! 

If your selected product is not lasting the distance, use an alternative method of control/prevention – this may be an earlier crutch or using an alternative product to manage with a protective period that fits tactically within your sheep management program – but be careful not to back yourself into a corner with incorrect product selection when it comes to WHP, ESI, or sheep/wool rehandle periods.  

Some other facets of management that will help: 

  • Burn or bury sheep carcases to dispose of maggots. 

  • Dispose of maggoty wool when treating struck sheep in a way that kills the maggots