Are worms a problem on your farm this year?
December 2018

With large parts of Victoria experiencing a drier than average spring or ongoing drought conditions, worms seem the lowest priority, but they can be real issue if left unmonitored.

To manage the risk of worms in your flock this summer, be mindful of the following issues:

Sheep in light condition (Condition Score 2 or less) and on short pasture are especially vulnerable to the effects of worms. In spring we try to put as much condition on stock as possible by utilising the abundant high quality feed available but condition can be hindered by appetite suppression, the main effect of subclinical infections of scour worms.

The other risk for worms after a dry winter is that with storms and heavy rain, large numbers of worm larvae are released from faecal pellets or pats and become concentrated in the short green grass. With every bite stock get a mouthful of larvae and if they are in poor condition they will also have low immunity. 

Most farms will have fewer worms in the system than an average or wetter year but unless you’re monitoring, you may have little idea what’s going on.

Worm control is always a balance between suppression of worm numbers and selection for resistance. Monitoring the worm egg count on your farm can prevent unnecessary drenching and in turn the development of resistance. After extended hot and dry conditions or when restocking after an extended destock, a drench can be highly selective for resistance. Worms that survive a drench are resistant and will form the basis of the future worm population on your farm. Considering these factors before drenching will help to control the development of resistance.    

If you experienced barber’s pole worm (BPW) in your sheep last year, there is a chance that you still have some in the system. BPW can survive over winter in Victoria as larvae on pasture and as adults in sheep. Generally there is a 90% reduction in larvae over winter, however the surviving larvae are enough to continue the infection and reinfect sheep over winter. Moisture levels over summer will determine whether BPW will be a problem, as numbers can quickly multiply with the right conditions.

When you do your worm monitoring ask for a ‘larval differential’ to identify if BPW is a problem.

Summer drenching is still the main pillar of our worm control program in Victoria. The summer drench is designed to reduce the accumulation of eggs over summer which can go on to cause worm problems after the autumn break. The time to drench is usually based on when pastures begin to hay off, as this will mean reduced larval pickup after drenching.  

Remember no Christmas dinner if you haven’t given your first summer drench!

Want to know more? Check out these websites:


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