He told ABC Radio the horse was unsteady on its feet, blind, had a fever, and pale membranes in its mouth. Its face was swollen and the animal had no gut noises. Its breathing and heart-rate were normal, however.
Pott, who wore protective gear in treating the animal, said he suspected hendra virus and took samples from the three-year-old.
The horse, on a property south of Townsville, died later that day.
It has been isolated from other horses on the property, he said.
Pott said he was worried in such cases about the potential exposure of people prior to the vet's arrival.
"I've arrived at situations in the past where children, or particularly the female members of the horse community, are sometimes cuddling their horse's muzzles or giving their horse a kiss on the chin.
"We discourage that activity these days, particularly if the horse is ill."
Queensland Health said the 10 people being tested for hendra had only low risk of exposure.
Meanwhile, federal independent MP Bob Katter has said he supported people's rights to cull potentially deadly animals on their own property, including bats, which are known to carry the hendra virus.
Authorities have resisted calls for bat culls in the past, amid concerns that stressing the species could result in them shedding even more virus.