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Australia's resource for control of worms, flies and lice in sheep,
and worms in goats

The Quick Quiz

This quick quiz tests your knowledge of sheep and goat parasites and their control. 

1. There are two common species of black scour worm, which one is more pathogenic and in what environments is it more common?

2. How can you use a paddock while it is being made low worm-risk?  

3. When hand jetting, what is a good indicator that the jetting fluid is being applied effectively?

4. Describe the withholding periods that apply to fly treatments.

>> Check the answers.

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State Outlooks for March 2019

From the editor

Much of the country is continuing dry with the prospect of an El Niño weather pattern during autumn and winter.

Producers in the eastern states contending with dry conditions might find value in the NSW state comments of the NSW district veterinarians Charlotte Cavanagh (Bourke), Jillian Kelly (Coonamble) and Erica Kennedy (Nyngan) regarding the correct diagnosis and treatment of scouring, or poor-doing sheep.

You may also like to revisit this article on worms in drought, as well as note the warning below.

Warning: drenching in drought is a leading cause of drench resistance!

Producers who need to drench sheep during these drought conditions should strongly consider using a 100% effective “quarantine drench” protocol, but also avoid drenching a whole adult mob (except where barber’s pole is an issue)—where possible, do not drench about 10% of the mob—make this judgement as you drench based on body condition and strength.

Why? After months of hot dry conditions with little pasture cover to protect larvae there is likely to be negligible worm larvae on the pasture; most worms on a property will be in the sheep! If the sheep are drenched before it rains, only drench-resistant worms will be in the sheep to reproduce and then contaminate the pasture when it next rains. Drenching under these conditions can therefore rapidly increase drench resistance on your property.

If a 100% effective drench is used, no resistant worms will be left in the sheep and only the odd ones from before (more susceptible worms) will be on the pasture. If not all sheep are drenched, the more susceptible population of worms those sheep are carrying will be the ones to start a new population rather than a highly resistant population left after a less than effective drench. Aim to leave a maximum of about 50 eggs per gram after treatment of these less-resistant worms—this won’t affect the sheep, but will help manage drench resistance.

[To calculate the number of sheep to leave undrenched based on a worm egg count: 5000 divided by your pre-drench worm egg count. example 1: 5000/200 epg = 25% to leave undrenched; example 2: 5000/450 epg = 11% to leave undrenched.]

If drenching is being considered, do a WormTest first, as worms may not be the problem. If drenching is indicated, choose an appropriate combination drench (or concurrently use more than one drench) with at least 4 highly effective components—one of these, if not two, should be monepantel (Zolvix®) or derquantel (Startect®).

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New South Wales
>> full report

With the prolonged drought conditions, producers are advised to worm test before giving the ‘routine’ drench.

>> full report

Worm test weaners and hoggets 4 weeks after the autumn break or after letting stock out of containment. Reducing worm egg levels in sheep now is the key to keeping pasture contamination levels low.

>> full report

Worm test mobs 4 weeks after storms, and worm test any individual animals that are doing poorly.

Western Australia
>> full report

Worm counts in sheep should now be very low or close to zero. If not, drench. By next month, a drench will have a limited effect in preventing winter worm burdens. Do a pre-lambing worm egg count 3–4 weeks before lambing.

>> full report

Give a second summer drench if you have not already done so. Fluke test any stock that has grazed fluke-prone paddocks since the beginning of December.  

South Australia
>> full report

Worm testing has indicated that many sheep mobs will need to be drenched despite negligible rainfall since mid-December.