Matt Colston, Elanco Ruminant Technical Consultant. In recent years there has been a lot of information produced around how to manage worm burdens in sheep in an efficient and sustainable way. Much of the data we now have shows there is an urgent need to change some of the tried and tested, traditional worm control routines, and that this needs to be done BEFORE there is a visible failure of the old system.
Why? Worm populations in sheep have the ability to, and already have, developed resistance to the wormer treatments we currently use. This creeps up slowly, reducing the productivity of the flock little by little, so that it goes unnoticed unless measures are in place to monitor growth rates, sales patterns, product and supplementary feed use. It’s an invisible problem until the wheels fall off completely.
Myth No 1 – I don’t have resistant worms on my farm.
As we’ve said, it’s an invisible problem until the wheels fall off, so you won’t know unless you’re checking to see what’s left behind after treatment. The data we have shows we’d find worms that were resistant to one or more of the wormer groups on 98%1 of farms if we looked for them, and on 77%1 of farms there would be worms resistant to two or more wormer groups.
Myth No 2 – My wormers are working as well as they’ve always done.
A recent survey2 showed that 86% of farmers thought their wormers were working as well as they always had. The same survey showed that the majority of farmers judged this on “the look and condition of the sheep”. Again, the data we have shows that lamb performance/growth rate will be reduced by up to 50%3 by a worm burden (e.g. resistant worms left behind after treatment), with no visible sign that the lambs are unhealthy. As we’ve said above, unless your checking, it’s an invisible problem until the wheels fall off.
Myth No 3 – I need to save the newer wormer groups to use if the older, cheaper wormers fail.
This is what we do with antibiotics, true, but this is NOT the same for wormers. Frequent use of the same active is one of the main drivers for worms to develop resistance. If we let the older three groups fail, we end up relying entirely on the newer group 4 (Zolvix™) and group 5 products. Over-use of these then makes their failure inevitable. Alternatively, integrating the newer actives now, as part of the worm control strategy for the farm will prolong the useful life of the older three groups, maintain effective levels of worm control, and not overuse the new actives.
Myth No 4 – The newer wormers are expensive, I can’t afford to use them.
You can’t afford not to!
What to do now?
If you don’t believe you have resistant worms on your farm or in your lambs, there are two ways you can make this invisible problem visible. Either do a drench check (mob samples for worm egg count) after each wormer treatment to see what’s been left behind (see www.farmanimalhealth.co.uk/sheep/sheep-worms or www.scops.org.uk for information on how to collect the samples) or use one of the newer wormers, eg Zolvix™ (Monepantel, Grp 4, Orange) as a break dose in the lambs in the latter part of the grazing season and see the difference for yourself.
References:
- Wales Against Anthelmintic Resistance Development (WAARD) Final Report 2015
- Attitudes to sheep wormers. Jan 2021, National Farm Research Unit
- www.scops.org.uk
For further information call Elanco Animal Health on +44 (0) 1256 353131 or write to Elanco UK AH Limited, Bartley Way, Bartley Wood Business Park, Hook RG27 9XA. ZOLVIX™ 25 mg/ml oral solution for sheep. Legal category: POM-VPS in UK. Information regarding the side effects, precautions, warnings and contra-indications can be found in product packaging and leaflets; further information can also be found in the Summary of Product Characteristics. Advice should be sought from the medicine prescriber. Zolvix, Elanco and the diagonal bar logo are trademarks of Elanco or its affiliates. Use medicines responsibly (www.noah.co.uk/responsible). © 2021 Elanco or its affiliates. PM-UK-21-0526. Date of Preparation: May 2021