Summer worm update warns of 'perfect storm' for internal parasites

"Consistently, internal parasites rank number two in the list of pandemic diseases and they only really run second to perinatal mortality," she said.

"Worms are a really, really costly thing, not only on a farm level but on a national industry level too. The real cost of worms is the production cost, and these might be things you don't realise."

Dr Kelly said the season being experienced in NSW was "the perfect storm" for worms. She said many areas across eastern Australia had, in the past two years, experienced wetter than average conditions, and in some cases, record rainfall totals.

"We have had virtually three wet summers in a row or three years of above average rainfall, which has allowed just enormous larval contamination on the paddocks... we haven't had any extreme heat to knock the larvae around so what we are seeing now is the problem that started three years ago," Dr Kelly said.

Dr Kelly said this was not just about barbers poll worm issue.

"Black scour worm is not a big issue in my part of the world, typically because it doesn't like the heat. So we don't see it every year, but it has been quite wet and mild so we have seen it persisting and hanging around from the winter and causing disease in sheep now," she said.

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Dr Kelly advised that some drenches, particularly those that targeted barbers pole worm, were not effective for black scour worm.

"If you haven't realised black scour worm is a problem and you have used some single action drenches to target your barbers poll, you may have left black scour worms behind," she said.

The black scour worm causes weight loss, damage and inflammation of the gut resulting in scouring, and there can be lethargy, collapse, and death in severe cases.

"You need to drench at much lower egg counts of black scour worm so the key point is, don't guess, get a worm test, and do a larval culture," Dr Kelly said.

Barbers pole worm was already proving lethal in areas like the Central West and Dr Kelly said since it was only November, it was shaping to become a particularly tricky season.

"A female can lay 10,000 eggs per day and the larvae can last a really long time on the paddocks so the issues we are seeing now were probably deposited last autumn or last spring," she said.

Dr Kelly said worm tests that find greater than 500 eggs per gram (epg) meant production loss, greater than 5000epg meant the sheep began to look sick, and greater than 10,000epg resulted in death.

"If you wait until they look sick, not only have you allowed those sheep to experience a production loss but also you've allowed them to be an egg factory that is wandering around your farm that's excreting thousands and thousands of eggs."