The withdrawal of Trodax from the animal health market has meant one less active ingredient is available to NI farmers for liver fluke control.
Trodax was the only nitroxynil-based flukicide which was licenced for use in NI. The injectable product killed liver fluke that were over six weeks of age and was most effective on larvae over nine weeks old.
With Trodax no longer being manufactured, it means there are only four active ingredients now licensed for liver fluke control in sheep in NI, with five active ingredients available for use in cattle.
At this time of year, triclabendazole-based flukicides are recommended for use on sheep farms. This is because these products kill all stages of liver fluke, provided there are no resistance issues on the farm.
Clostantel-based flukicides can also be used in the autumn, although these products will not kill fluke under two weeks of age, and they are most effective on larvae over four weeks old.
The other two active ingredients which are available to NI sheep farmers for liver fluke treatments are oxyclozanide and albendazole.
While oxyclozanide is effective against mature liver fluke, it is the only active ingredient that can be used for rumen fluke control. For this reason, it is generally advised not to use oxyclozanide for treatments that only aim to control liver fluke in livestock.
As well as being effective against mature liver fluke over nine weeks of age, albendazole-based products can be used for the control of roundworm, lungworm, and tapeworm.
The optimal time to use these products in sheep is in the spring or summer.
Farmers in the Republic of Ireland have access to rafoxanide-based flukicides, and these products can be used in NI and the rest of the UK under a special import certificate.
However, vets have warned against only using rafoxanide and closantel-based products on farms, especially where there are already resistance issues with triclabendazole. This is because rafoxanide and closantel are closely related and so developing resistance to one of these active ingredients could also create resistance to the other.
Triclabendazole, closantel, albendazole and oxyclozanide are all licenced for use in both sheep and cattle in NI. The fifth active ingredient which can be used for liver fluke control in cattle, but not sheep, is clorsulon.
This injectable flukicide is effective against mature liver fluke and most clorsulon products on the market also contain ivermectin for the control of other parasites such as roundworms and lungworms.