After three weeks of comprehensive laboratory testing, Biosecurity Queensland believes that either scrub tick infestation or botulism was the likely cause of the deaths of 22 horses at a Kooralbyn property.

Chief Biosecurity Officer Jim Thompson said both conditions caused progressive muscularparalysis, as was seen with these horses, and it was often hard to differentiate betweenthe two.

“Botulism is a bacteria that lives in soil and produces a toxin that affects the nervoussystem if ingested,” he said.

“The other likely scenario is scrub tick poisoning. Witnesses have reported that thehorses first noticed to be in distress on Thursday 6 October had been carrying largenumbers of ticks.

“Fatal infestations of scrub tick on adult horses have been recorded in the past.

“This has been an unusual and complex case. Biosecurity Queensland worked closely with theattending private veterinarian and Queensland Health to test a range of samples from thehorses and the paddock where they were kept.

“Despite carrying out such a thorough investigation, we know from experience that testresults don’t always pinpoint an exact cause of death.

“However based on the circumstances, Biosecurity Queensland believes scrub ticks orbotulism were most likely responsible in this case.”

Test results have excluded:

· Hendra virus
· pesticides
· heavy metals (arsenic, lead, cyanide, nitrate)
· toxic plants
· water contamination
· deliberate poisoning.

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