Closantel overdose can lead to blindness in sheep

Sheep farmers are strongly advised to exercise caution when using deworming agents (flucicides) containing the active ingredient closantel.

Giving an animal too much closantel can lead to permanent blindness, the UK-based Organization for Sustainable Control of Sheep Parasites (SCOPS) has warned.

There have been reports of overdose on some sheep farms across the UK in recent months, according to the animal health authority.

Closantel, an important active element in the fight against internal parasites, is contained in Supaverm and Flukiver, Solantel, Closamectin and Closiver.

Speaking on behalf of SCOPS, independent sheep consultant Leslie Stubbings says that animals should be given closantel strictly according to their weight: is to ensure that the animals receive the correct dose.”

The current industry recommendation is to dose the anthelmintic or flucicide by separating sheep into weight groups and adjusting the dosage accordingly. “This is safer than giving the same dose to all sheep and compromising animal health with lighter weight excess closantel. Any adverse reactions to closantel should also be closely monitored. This is not advice to avoid the product at all - just a reminder of the risks associated with sheep farmers not weighing animals and giving them too much internal parasite medication," Stubbings concluded.