More than a third of NZ sheep farms are resistant to triple combination drenches, which is costing the average farm $70,000 a year in lost production.
The problem is growing with the latest drench efficacy test survey from animal diagnostics company Techion revealing 34% of farms are resistant to triple active drenches, up from 30% last year.
Techion founder and managing director Greg Mirams estimates that nationally the annual cost of lost production to the sheep industry from drench failure is $110 million.
He said the problem has reached such a scale that it requires a united industry approach.
“The industry needs to look at this issue. We need everybody to realise what we have got here.”
Every year Techion analyses more than 50,000 faecal egg count (FEC) tests at its Mosgiel laboratory through its network of FECPAK users, and Faecal Egg Count Reduction Test (FECRT) tests through its DrenchSmart service.
Results for the first seven months of this year reveals that triple drenches Benzimidazoles (BZ), Levamisole (Lev) and Abamectin (Aba), were failing on 34% of NZ sheep farms.
Mirams said other common drench options fared no better with BZ-Lev combinations failing on 47% of properties and Lev-Aba combinations failing on 39% of properties tested.
“Another significantly worrying trend in this year’s results is that drenches including Monepantel-Abamectin, sold as Zolvix, and Derquantel-Abamectin, sold as Startect, are showing signs of diminished efficacy on a growing number of properties.”
Mirams said it is unclear why this is happening, but there appears to be an increasing failure of the Abamectin active on properties that have a parasite population that is highly resistant to other drench actives.
Until now the newer novel active drenches, such as those containing Monepantel and Derquantel, have been considered the gold standard for quarantine drenching livestock or an effective option when farmers have widespread drench resistance.
He said these actives are expensive and, at times, challenging to source but without access to effective drenches, farmers have limited options.
Also of concern is the growing resistance to triple drenches of the trichostrongylus parasite in autumn, which could result in lower conception rates for hoggets and two-tooth ewes.
Without access to effective drenches, Mirams said, farmers may need to consider integrated parasite management systems such as using novel forages, genetics and grazing management.
He said the issue need not be a disaster but requires a change in mindset to first establish if there is a problem and, if so, what management options they have.
Mirams said with a one-in-three chance that bought-in stock are coming from a farm with triple resistance, it is essential farmers have strict quarantine procedures so imported animals do not bring resistant parasites with them.
Given low product returns, Mirams said paying for and using drenches without checking they are working could be wasting time and money.
