Over the past 15 years, our lab has diagnosed many cases of barber’s pole worm (Haemonchus) in sheep and cattle. Long regarded as a subtropical worm, Haemonchus has a life cycle that is favoured by warm, wet weather. In fact, the eggs of barber’s pole worms die in 5 days if the weather is dry or cold. However, if they do get through the difficult egg stage and hatch, the larvae will contaminate pastures for many months, even over winter.
The past 5 years have given us plenty of summer rain, even in southern areas. As a result, barber’s pole worms have spread far and wide and even become established in cooler inland areas where they were previously rarely seen.
This year at Dawbuts, we have had many tests showing winter Haemonchus in both sheep and cattle, including some which were tested post-drench with a long-acting product, within its label protection period.
An example is a sheep sample from Yass, NSW tested in late June 2024 with an average worm egg count of 1053 per gram and larval culture of 96% Haemonchus and 4% Teladorsagia. This mob had been drenched in mid-April 2024 with Zolvix and Moxidectin Long-Acting.
A similar case came from a farm located at about 800m altitude in the Southern Tablelands. A mob of Merino hogget ewes that had been treated only 4w previously with a double treatment of a long-acting closantel with abamectin, along with a combination levamisole and BZ had a WEC (Worm Egg Count) of average 730 eggs per gram (range 200 to 1,850) with 81% Haemonchus.
A third case came from cattle in the NSW Central Tablelands, tested in mid-May with a 72 eggs per gram average, positive fluke result and larval culture displaying 32 % Haemonchus and 68% Cooperia. This mob had been drenched with Moxi LA + a triclabendazole-oxfendazole combination in mid-March 2024. This not only shows that barber’s pole and Cooperia worms were re-appearing within the label protection period of the long-acting product, but that the liver fluke on that property appeared to have survived a treatment with a combination flukicide.
The above cases happened after producers used ‘best-practice’ techniques, i.e. using the long-acting moxidectin injection or closantel with a ‘primer’ treatment. However, the re-appearance of barber’s pole worms within the protection period indicates advanced resistance in this parasite.
This presence of Haemonchus in the colder months could be a result of an increase in climate temperatures, high worm burdens on pastures and/or increased worm resistance to drenches. Regular testing even in the colder months is key to monitoring your livestock for parasites on your property.
By Lauren Hughes BNatSc(AnSc), BSc(Zool)
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