Cushing’s disease is now well recognised worldwide. It appears in older animals and causes retention of the winter coat, increased thirst, muscle wastage, weight loss and depression.

There has also been some suspicion that Cushing’s cases suffer more from intestinal worms than other horses, although until recently this has not been proved.

Vets at Oklahoma State University have studied the worm burdens of Cushing’s horses and their response to worming with ivermectin.

The Cushing’s disease animals were matched with healthy horses of similar type and age on the same premises.

The vets measured faecal worm egg counts from all the horses before treatment and then measured the faecal worm egg counts every two weeks for the next 12 weeks. The study showed no evidence of worm resistance to ivermectin.

The horses and ponies with Cushing’s tended to have higher worm egg counts before the treatment than their healthy counterparts but, significantly, the Cushing’s animals developed significant worm egg counts again more rapidly after worming than the healthy horses.

The research showed that age alone did not increase the susceptibility of a horse to worms, but having Cushing’s did.

The scientists concluded that horses with this problem should be more carefully monitored for worms and may need more aggressive worm control measures than healthy horses of the same age. Consult your vet before taking any action.

This is an extract from a feature on the latest veterinary research and developments, first published in Horse & Hound (9 September, ’10)