A product that can treat both lice and worms at the same time is a great convenience, but it could make worm control harder in the long term if precautions are not taken to minimise the development of “drench resistance”.
Maverick®, from Coopers Animal Health, is a unique product for sheep, containing abamectin—a macrocyclic lactone—that is applied as a pour on backline to kill lice, but it is also absorbed into the bloodstream and kills susceptible roundworms.
Fortunately, no lice resistant to abamectin have been found, but that’s not the case with worms.
Resistance of black scour worm to the macrocyclic lactones has been reported in Australia, but confirmed cases are still uncommon and likely to exist on few properties. However, many properties in Australia have resistant brown stomach worm. Resistance by barber’s pole worm to this group occurs on most properties in summer rainfall regions and on many properties in other regions.
If a lice treatment is your first priority, consult the LiceBoss Treatment Guide and then decide whether your sheep really need to be treated for worms by referring to the Drench Decision Guide for your region.
If a lice treatment is needed, but a worm treatment isn’t necessary, consider an alternative product to avoid giving an unnecessary ‘drench’. Each time a drench is used it provides the opportunity for resistant worms to survive, reproduce and build up on your property.
For properties in the pastoral or rangelands regions that very seldom drench, but do require a lice treatment, it is likely that your sheep will have low numbers of worms and the drench resistance impact of using a single-active product such as Maverick needs to be managed. However, if drenches are not used, then using Maverick for a lice treatment should not create any problems for worm control.
Where a concurrent worm treatment is required, WormBoss recommends 3 strategies that are equally important and highly effective at reducing the development of drench resistance:
Maverick ticks the box as a short-acting treatment, but it is not a combination product, as it only contains abamectin, and you need to know if it is effective on your property.
A Drench Resistance Test of single-active products is the best method to determine effectiveness of any drench, but this can also be done, albeit with less accuracy, with a DrenchCheck-Day10 (follow the links to find out how they are done). Calculate the efficacy of combination products from single-active DrenchTest results and then choose products that are most effective.
So, if Maverick is a good fit for your lice and worm control, WormBoss recommends that you concurrently give another highly effective oral drench (from a drench group other than the MLs) so that sheep receive 2 or more unrelated drench actives.
In summary, if you require drenches to control worms, and you plan to use Maverick for lice control: