15 December 2008

Researchers from The University of Queensland have found hairy caterpillars are responsible for causing abortions in Australian mares.

Dr Judy Cawdell-Smith and Professor Wayne Bryden, from UQ’s School of Animal Studies, found mares exposed to processionary caterpillars were likely to miscarry.

"This is an unusual form of abortion that was first reported in Australia in 2004 and is similar to a condition reported in Kentucky in 2002," Dr Cawdell-Smith said.

"Researchers in Kentucky identified Eastern Tent Caterpillars as the cause of the US equine condition, Mare Reproductive Loss Syndrome."

Similar equine abortion cases were reported in the Hunter Valley in 2004.

"Studies conducted by veterinary epidemiologist, Professor Nigel Perkins, suggested the abortions were caused by caterpillars or poisonous plants," Professor Bryden said.

"No poisonous plants were found on any of the stud farms where mares aborted.

"Caterpillars were identified as the cause of the US problem but the same caterpillars don’t exist in Australia.

"However, other related caterpillars were found on the affected Australian stud farms.

"If you’ve ever seen a hairy caterpillar, it is unlikely that a horse would eat a whole one.

"What’s more likely is that the caterpillar’s exoskeleton – which is much harder to see in the grass – is picked up by the horse while it is grazing.

"In our studies, both whole caterpillars and exoskeleton caused mares to abort."

The researchers believe ingestion of the caterpillar changes the permeability of the intestinal wall, allowing bacteria to pass into the horse’s circulation and through the placenta.

"The subsequent infection caused by the bacteria in the fetus results in abortion," Dr Cawdell-Smith said.

"These bacteria are found in the intestine of mares and normally don’t cause a problem.

"Interestingly, mares that abort have no ill effects or evidence of illness."

Funded by the Rural Industries Research and Development Corporation and the Hunter Valley Equine Research Centre, Professor Bryden and Dr Cawdell-Smith have conducted research in this area since 2006.

Media: Dr Cawdell-Smith (0418 631 646), Professor Bryden (0413 808 830) or Penny Robinson at UQ Communications (07 3365 9723)