While use of the two newer wormer groups, 4-AD [orange] and 5-SI [purple] has more than doubled in the last three years, the Sustainable Control of Parasites in Sheep (SCOPS) says sheep farmers could still harness their potential more.
In an open letter to industry, the National Sheep Association (NSA), SCOPS, Moredun and the Sheep Veterinary Society (SVS) is urging more sheep farmers to follow SCOPS advice and integrate the two newer groups into their worm control programmes.
SCOPS advises that the group 4-AD and 5-SI wormers should be used as quarantine treatments for all incoming sheep and as a one-off treatment for lambs, in the latter part of the grazing season. The idea being that the two newer wormer groups are not left underutilised until other groups, 1-BZ [white], 2-LV [yellow] and 3-ML [clear], are no longer effective.
Speaking in a webinar hostes by NSA, Moredun and Elanco, Dr David Bartley of Moredun highlighted a lack of effective quarantine treatment among drivers of resistance.
Mr Bartley said: “If new or returning animals are not effectively treated when returning on-farm, the danger is bringing in resistance or other parasites which were not there before.
“The current advice for returning stock [when it comes to wormers] is to treat with a 4-AD and 5-SI separately, ideally then hold these animals off pasture for 24-48 hours and, if possible, to then turn out on to higher challenge pasture to avoid any potential contamination of lower challenge areas.”
Matt Colston of Elanco later reiterated SCOPS advice, saying that group 4-AD and 5-SI wormers should be included in the worm control plan for all farms now, before there is an obvious failure of the other three groups available.
Mr Colston said: “Groups 1-BZ, 2-LV, and 3-ML have been around for many years and for most sheep farms have been the mainstay of worm control. This has led to a growing, widespread issue of resistance to these actives, but it does not mean they do not have any use on farms now.
“Groups 4-AD and 5-SI should be used, but only at specific times, one being as a quarantine treatment and the other as a mid-late season break dose for lambs. This would include all lambs on the farm in the latter part of the grazing season, the idea being to remove the worms that have been left behind by previous treatments.”
Other measures to improve worm control highlighted by Mr Colston included grazing management, carrying out worm egg counts and monitoring growth rates to identify underperformers for potential targeted treatment.
The mid-late season break dose for lambs and as part of the quarantine treatments are the only generally recommended times to use these newer products. To avoid the risk of resistance developing to the two newer groups, industry bodies said they should not be used at other times without detailed advice from a consultant or farm vet.