The research was carried out by Dr Craig Reinemeyer and others at East Tennessee Clinical Research Inc.
In separate studies, the researchers examined the effectiveness of two dewormers against Oxyuris equi (equine pinworms), and Parascaris equorum (ascarids or roundworms) known to be resistant to macrocyclic lactones (the ivermectin-related family).
Equine pinworms rarely causes serious problems for the horse, but does cause irritation when the female lays the sticky eggs on the skin around the anus of the host. It has been assumed that most routine dewormers will control it.
Twenty-one horses with naturally acquired pinworm infections were divided into three groups. One was treated with pyrantel pamoate (at 13.2mg/kg - the dose used for tapeworms); one group received ivermectin (200mcg/kg) and the third group was left untreated.
Fourteen days later, post mortem examination of large intestinal contents showed that both dewormers produced a significant reduction in numbers of pinworms.
Pyrantel pamoate was 91.2 per cent effective, and ivermectin 96.0 per cent effective against the adult worms. Both products were more than 99 per cent effective against the fourth-stage pinworm larvae.
(Editorial) Hard-pressed horse-owners are facing a steep rise in feed-stuff prices