The owner of 22 horses which died on a southeast Queensland property has questioned a finding that scrub ticks or botulism probably caused the deaths.
Steve Hogno said tests of horse-hair samples sent to a US laboratory had turned up high levels of heavy metals including manganese and zinc, among others.
“They’re saying they’ve got some of the highest levels of heavy metals they’ve even seen,” Hogno told AAP. “Now we’ve got to try and find out where they’ve come from.”
The US laboratory had indicated that ingestion of a toxic weed or outside intervention could have caused the high metal levels, Hogno said, and that he did not know why Biosecurity Queensland had reached such a drastically different conclusion.“The chief pathologist with Biosecurity Queensland is saying what world-class facilities they have, but it seems they’ve drawn a blank and said ‘ticks will do’,” Hogno said.
Twenty-two quarter horses from a herd of 25 died within five days of each other at a property west of the Gold Coast last month, baffling vets and Hogno.
Biosecurity Queensland has said that scrub ticks or botulism were probably behind the deaths, adding that three weeks of lab tests on the animals ruled out such possible causes as Hendra virus, toxic plants, water contamination and deliberate poisoning.
Chief biosecurity officer Jim Thompson said both ticks and botulism could have caused the progressive muscular paralysis seen in the horses, and it was often hard to differentiate between the two.
Botulism is a bacterium that lives in soil and produces a toxin that affects the nervous system if ingested.
Thompson said scrub tick infestations represented the other likely scenario and fatal infestations of scrub tick on adult horses had been recorded.
“Witnesses have reported that the horses first noticed to be in distress on Thursday, October 6, had been carrying large numbers of ticks,” he said.
However he warned test results didn’t always reveal the exact cause of death.
The Biosecurity Queensland tests also ruled out contamination from pesticides and heavy metals, Mr Thompson said.
The first horses began dying in a paddock at Kooralbyn, 90km west of the Gold Coast, on October 6, and within five days just three horses from the herd of 25 had survived.
Speculation followed that noxious weeds, contaminated water and even deliberate poisoning were behind the deaths.