Thursday, April 25, 2024

Concerns over increase in drench resistance

Neal Wallace
Sheep farmers risk inflating a current $48 million annual drench resistance problem into a $128m financial burden, unless they closely manage the efficacy of remaining drenches.
Reading Time: 2 minutes

That is the conclusion of Techion founder and chief executive Greg Mirams, who has analysed 15 years of data which shows 40% of sheep farms could soon be resistant to triple combination drenches unless there is careful management.

He says in 2005, resistance was low to non-existent but tests now show double combination drenches are failing on between 20% and 43% of farms and triple combinations on 15%.

“We’re not trying to be alarmists, we’re simply drawing upon a significant body of data collected over a decade-and-a-half which proves, without a doubt, drench resistance in New Zealand is increasing rapidly,” he said.

“If farmers continue to use drenches the way they have for the past four decades, drench resistance will continue to develop.

“The problem is impacting animal welfare and performance, farm productivity and hurting New Zealand meat exports.”

Undetected or unmanaged drench resistance can reduce carcass returns by 14% which, when extrapolated over prices for the 18 million lambs slaughtered last year, equates to a cost across the sector of $48m, or $71,000 for a farm selling 4000 lambs.

“You don’t see an animal dying or any visual signs, but your lambs are growing at 180 grams a day instead of 270 grams a day,” he said.

Should resistance increase to 40% of farms as Mirams fears, he estimates the loss of productivity for the sector will increase to $128m a year.

He says drench resistance is not the end of the world as it can be managed, but farmers first need to know the extent of any problem by testing for resistant parasites.

Because 95% of parasites live on pasture as larvae, it is the farms that develop resistance with sheep just being carriers of parasites, and that means replacing the flock is not a solution.

Greg Miriams | September 07, 2020 from GlobalHQ on Vimeo.

“It takes a rethink but it’s not the end of the world, farmers can farm through this,” he said.

That rethink requires farmers to be proactive instead of reactive and to focus on managing the larvae not the parasites.

Once farmers know the degree of any resistance, Mirams says solutions include the strategic use of cross grazing sheep and cattle, using high protein forage, such as red clover and plantain which do not harbour parasites to the same degree, and breeding parasite-resistant stock.

He quotes advice from Dr Ray Kaplan, a parasitologist from the University of Georgia in the USA, about how to slow the onset of resistance.

Kaplan recommends testing for resistance every two to three years to determine the drenches that work the best.

Animals new to a farm should be quarantined and treated with the most effective drench available.

They should have faecal egg counts before and after drenching, and only join the rest of the flock if the count is negative after 14 days. 

Techion is a parasite diagnostic and management company and Mirams says having analysed 15 years of data, he was concerned at the pace with which parasite resistance has accelerated in the past four years.

Up to 2008, there was almost no resistance to double and triple acting drenches, but that has changed markedly since 2016.

It costs between $200m and $2.5 billion to develop a new animal anthelmintic, and Mirams says given the limited market and other drug development opportunities, new products are unlikely.

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