Your Local Elanco Territory Manager can help you to check the efficacy of your drench with a free DrenchCheck via the Zolvix Plus Challenge.

INTERNAL parasites cost Australian sheep and wool producers an average of $28,000 in lost productivity and a further $5000 in treatment costs every year,(1) yet the majority are unaware of the resistance status of the worm population on their farm or the efficacy of their most recent drench.

Elanco Brand Manager – Sheep, David Rathbone, says drench resistance is one of the biggest challenges facing sheep and wool producers.

“A national study identified widespread single, double and triple resistance to all older active ingredients, including moxidectin,” he says.(2)

“This report was compiled more than a decade ago and there is no reason why this situation would have improved.

“Despite this, most sheep and wool producers do not know the efficacy of their current drench or incorrectly believe it is still fully effective.”

What is ‘resistance’?

A drench is deemed to be ‘resistant’ if it fails to reduce the worm burden by more than 95pc (with appropriate statistical considerations).(3)

“Resistance is not as simple as saying a drench ‘works’ or it doesn’t,” Dave says.

“Some drenches might have 90 percent efficacy; some might have 80pc efficacy, and some might have 50pc.

“All of these drenches are still ‘working’ to some degree, but any reduction in efficacy can impact the health and productivity of sheep.

“Even mild or moderate levels of drench resistance can result in a significant economic loss to the producer and make resistance even worse.”(4)

Concerning results

Elanco assisted 171 lamb and wool producers to undertake DrenchChecks between 2022 and 2024.(5)

A DrenchCheck determines the efficacy of a drench against the worm burden present at the time of treatment by comparing worm egg counts in faeces before and after drenching.

The presence of any worm eggs – even very low counts – 10 to 14 days after drenching may indicate the presence of resistance.

Elanco is committed to helping customers to get the best outcome from their investment in Elanco’s range of animal health products.

This program found that almost half of all single-active, dual-active, three-way and four-way combination drenches did not deliver fully effective worm control.

In 77 of these checks (45pc), the tested drench did not reduce the overall worm burden or an individual worms species by more than 95pc.

Of particular concern, 22 of the 49 checks conducted on abamectin-based triple drenches and 7 of the 18 checks conducted on moxidectin-based triple drenches showed evidence of resistance.

“There is a widespread belief that triple combinations are a ‘silver bullet’ for addressing drench resistance when this is not the case,” Dave says.

“Triple combinations have a very important role in helping to maintain the life of available chemistry – but only if they are known to be effective.”

Free DrenchCheck

Sheep and wool producers who would like to examine the efficacy of their drench are encouraged to undertake a free DrenchCheck via the Zolvix^™ Plus Challenge.

“Elanco is committed to helping our customers to get the best outcome from their investment in animal health products,” Dave says.

“To participate, register online before your next planned drench.(6)

“A DrenchCheck is the first step in helping to determine the efficacy of your current drench,” Dave says.

Zolvix Plus from Elanco is ideal for use if drench resistance status is unknown.

This unique formulation delivers the power of monepantel, the first member of the ‘orange’ drench class(7), in combination with abamectin.

Monepantel’s unique mode of action provides >99.9pc efficacy against a broad spectrum of internal parasites in sheep, including single, double and triple strains.(8-10)

For more information, please contact your local Elanco Territory Manager or visit zolvixplusrewards.com.au

Always read and follow label directions. Good agricultural practice is essential for optimal worm control.

References: 1. Based on estimated production and treatment costs of internal parasites in sheep (Shephard R, et al. (2022). Priority list of endemic diseases for the red meat industry – 2022 update. MLA report B.AHE.0327; 2022. Meat and Livestock Australia Limited) and 20,147 agricultural businesses involved in the sheep industry (Fast Facts – Australia’s sheep meat industry 2024. Meat & Livestock Australia).  2. Playford, M.C. et al. (2014). Prevalence and severity of anthelmintic resistance in ovine gastrointestinal nematodes in Australia (2009-2012). Aust Vet J 92: 464-471. 3. Coles, G. et al. (2006). The detection of anthelmintic resistance in nematodes of veterinary importance. Veterinary Parasitology. 136:167-185. 4. Besier, R.B., et al. (1996). Drench resistance – a large economic cost. J Agric West Aust 37:60–63. 5. Elanco National Drench Check Summary 2022-2024 PM-AU-25-0128. 6. Terms and condition apply. Visit www.zolvixplusrewards.com.au for terms and conditions. 7. Monepantel is a member of the amino-acetonitrile derivative (AAD or ‘orange’) family of anthelmintics. 8. Hosking, B.C. et al. (2010). A pooled analysis of the efficacy of monepantel, an amino-acetonitrile derivative against gastrointestinal nematodes of sheep. Parasitol Res 106:529-532. 9. Refer to registered label. 10. Baker, K.E. et al. (2012). Efficacy of monepantel and anthelmintic combinations against multiple-resistant Haemonchus contortus in sheep, including characterisation of the nematode isolate. Vet Para 186(3–4): 513–517.

Zolvix Plus contains 25 g/L monepantel and 2 g/L abamectin. Zolvix™, Elanco and the diagonal bar logo are trademarks of Elanco or its affiliates. ©2025 Elanco or its affiliates. EAH25225. PM-AU-25-0243.