Sheep farmers are being urged to incorporate new actives into worming programmes as part of an initiative to support crucial productivity metrics and help slow the rate of anthelmintic resistance.
Wormer resistance is an invisible problem and it can be tempting to continue with a similar worming routine year-onyear in the belief that the existing wormer groups being used are still working as well as they always had.
However, in the last 10 years, the number of reports of resistance to the three older classes of wormer have been increasing.
Some 94 per cent of farms have been found to have resistance to white wormers, 68 per cent to yellow wormers, 51 per cent to ivermectin and 19 per cent to moxidectin, with just 2 per cent of farms with no detectable resistance.1
Not only do these figures suggest that lamb growth rates are inadvertently taking a hit due to the survival of resistant worms, but they also point to an anthelmintic resistance crisis if the industry continues along the same trajectory.
It is therefore crucial that all sheep farmers act now and incorporate a 4-AD, monepantel, Zolvix™ or a 5-SI wormer into annual worming programmes – an approach endorsed by the National Sheep Association, Moredun Research Institute, Sheep Veterinary Society and SCOPS.
Using one of these newer wormer actives will not only support productivity and profitability in your flock by clearing out any resistant worms, but crucially it will slow the development of resistance to the older group 1, 2, and 3 wormers.
 Wales Against Anthelmintic Resistance Development (WAARD) Final Report 2015
While most farmers will have heard of Zolvix (4-AD orange wormer) many are uncertain of how and when it should be incorporated into an annual worming programme.
Matt Colston, vet at Elanco Animal Health, answers some common questions about the use of Zolvix.
It should be used on all sheep farms every year at two key points within a worm control plan - for all incoming sheep as part of their quarantine treatment and as a one-off annual treatment for lambs in the latter part of the grazing season.
A break dose is when the product is used in lambs in the latter part of the grazing season to remove the resistant worms left behind by previous treatments.
As above, use it for one dose during the mid-late grazing season.
Other wormer groups should be used as appropriate through the rest of the grazing season.
No, it is never a good idea to dose lambs (with any wormer) and move them straight to clean grazing.
Doing this will only take worms that have survived the treatment onto the new pasture.
It is best to return to the same field for four to five days before moving to cleaner grazing to avoid the risk of selecting for resistance.
Using any wormer when the worm burden is low is a waste of time and money.
Wait until there are enough worms present in the lambs for the treatment to give a benefit (i.e.
when the worm egg count is higher).
Chances are you do already have resistant worms on the farm, you just won’t see the problem unless you are testing regularly.
But even if testing confirms there are no resistant worms present, including Zolvix in your worming plans now will reduce the risk of resistance developing to the three older wormer groups.
Except for incoming sheep as part of their quarantine treatment, fit healthy adult sheep should not normally need any routine treatment with any other wormer.
This is because adult sheep usually have developed good immunity to gut worms and have the worm burden under control.
On farms with multiple resistance issues and when adult sheep are under stress, treatment of adult sheep may be required.
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 groups.
Over-use of these then makes their failure inevitable.
Alternatively, integrating orange wormers 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.
For further information call Elanco Animal Health on +44 (0)1256 353 131 or write to Elanco UK AH Limited, Bartley Way, Bartley Wood Business Park, Hook RG27 9XA.
ZOLVIX™ 25mg/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.
Anthelmintic resistance is one of the biggest challenges facing the health and profitability of the entire sheep industry, with 98% of farms identifying some level of resistance to group 1, 2 or 3 wormers.
Elanco’s ‘Wake Up to Worm Resistance’ campaign has been launched to raise awareness and tackle this major issue.