The banning from sale of two commonly used slow-release anthelmintic animal boluses is a symptom of a much greater risk from growing internal parasite resistance in livestock.
AgResearch scientist Dave Leathwick said by some calculations a third of New Zealand sheep farms have worms resistant to all three drench families, and it is a problem that is quickly spreading.
“For decades we have had an obsession to use drench to solve all our problems,” Leathwick said.
“Now we have a situation where it doesn’t work anymore and our farming philosophy has to change.”
Leathwick was responding to news that NZ Food Safety Agricultural Compounds and Veterinary Medicines (ACVM) has banned the sale of Boehringer Ingelheim’s Bionic Plus and Bionic Plus Hogget slow-release animal boluses.
It has also announced an investigation into 16 other anthelmintic slow-release ruminal boluses registered for use in sheep and cattle.
Leathwick said farmers have continued to buy and use these products even though they are increasingly not working.
“The future for NZ sheep farming is not which drench or capsule do they use, but how to run a farm without the need to use them because they are not working.”
The sales ban of the two products follows an incident last year when treated animals in multiple flocks were found with high parasites levels due to the release of sub-therapeutic levels of active ingredients.
An estimated 200,000 capsules were implicated.
Boehringer Ingelheim placed a voluntary stop sale on sales last November and subsequently asked vets to notify farmers not to use the products.
Concerned about residue, ACVM imposed a withholding period of 154 days for treated stock, up from the standard withholding period of 126 days.
Sales have now been banned while the products are reassessed in terms of risk to animal welfare and trade.
Ginny Dodunski, a sheep veterinarian and manager of the Beef + Lamb New Zealand-funded Wormwise programme, fears farmers may continue to use stored stocks despite growing resistance issues.
“Farmers who have relied on these products are reluctant to stop using them, either because of their farming system or the type of stock they are running,” she said.
As farmers head into winter and lambing, she said they need to do what they can to get through, but in the long term they will need alternatives.
One cost-effective option is to use nitrogen to boost ewe body condition score to above 2.5 as lighter conditioned sheep are twice as likely to be culled, dead or missing by weaning.
Dodunski said the unavailability of bionic boluses is both a threat and an opportunity.
“To farm successfully when these products are withdrawn from a system involves a strong focus on improving ewe body condition and setting up the farm to feed ewes properly coming into lambing and early lactation.”
Bionic Plus is distributed by Boehringer Ingelheim but manufactured in Auckland by Argenta. Phil Huse, Argenta’s chief commercial officer, said in a statement that these and similar products have offered long-term parasite control in the NZ market for more than 20 years.
On receiving notification from the ACVM, Argenta, with Boehringer Ingelheim, contacted all vet customers to advise them of the requirements and request they contact farmers to immediately stop using the products until further advice.
Huse said Argenta has set up a research team that is actively working with Boehringer Ingelheim and the ACVM to investigate the cause of the product variability and identify the actions required to update the registration and return the product to market.