Mystery illness kills 16 horses in Qld

SYDNEY (AAP) - Oct 07 - A mystery illness has killed 16 quarter horses on a property west of the Gold Coast, and vets and Biosecurity Queensland are trying to pinpoint why so many healthy animals died so quickly.
With Hendra virus ruled out as the cause on Friday, scientists and local vets are leaning towards the possibility the animals may have fallen victim to some type of toxic weed.
Devastated owner Steve Hogno says his horses started dropping dead on Thursday.
Mr Hogno, who was working at a mine site in Western Australia, returned to his home at Kooralbyn near Beaudesert on Friday morning.
"They appear to have died quickly. They just dropped, and that was that," he told AAP.
"The Hendra tests have come back clear. That still leaves it a mystery as to what caused the problem, but at least it does put the local community's mind to rest a little bit, knowing there's not Hendra in the area."
Autopsies have been performed on some of the dead quarter horses, but Dr David Ahern from Scenic Rim Veterinary Service says results won't be known until Monday or Tuesday.
"Samples of brain, lungs, spleen and other organs have been taken, and they have to be fixed in formalin for a few days before thin slices can be taken and examined under a microscope to see if an infectious disease or a toxin has killed the horses," he said.
Queensland's chief vet Rick Symons said there was no sign of foul play and the RSPCA has ruled out neglect.
Locals noticed five dead and three sick fillies and mares, which were infested with ticks, in a paddock near Kooralbyn on Thursday.
The three sick horses were euthanased, but the death toll increased to 12 on Friday morning. By late afternoon four more had been put down, lifting the death toll to 16 with only nine surviving.
"We've moved those last horses out of the paddock and I think they'll be all right," Mr Hogno said.
"There's no guarantees for a couple of days, but I'm fairly hopeful they'll be okay."
Dr Ahern said he doubted speculation that paralysis ticks may be responsible for killing the horses, with some kind of toxin a more likely cause.
"The progression of the illness is not typical of what you'd expect from paralysis ticks," he said.
"Paralysis ticks very infrequently cause paralysis in adult horses. In the last five years I've seen two in this district, and in the five years before that I saw none, so the deaths of so many horses from ticks would be possible but extremely unlikely."
Mr Hogno said weeds were the most likely cause.
"It's looking very much like a poisonous weed that was in the paddock that nobody knew about," he said.
Amanda Scoble, who lives nearby, said locals were very relieved the cause was not Hendra.
"It's a massive relief. We didn't go and feed our horses yesterday, fearing it could be in the air, but now we can go back and check them to make sure they're all right.
Heather Mackay from Galloping Hooves Equine Rescue said Mr Hogno's horses had been in good condition and well looked after.
"I've never known a case where ticks have brought down so many horses.
"To bring down one is an event, but to kill this many, I don't know, I think poisoning of some kind is more likely."
Doug Wilson said he saw three of the horses lying in the paddock near the side of the road on Thursday morning.
"When you see horses down you usually try to spook them to make them get up, so you know they're all right, but this lot didn't so I went into the paddock and they were in quite a bad way.
"It's distressing to watch a beautiful horse die in front of you, choking to death, and there's nothing you can do."