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Home Chemical Groups and Actives for Cattle Macrocyclic Lactones (ML)

Macrocyclic Lactones (ML)

What do they treat?

√ Roundworm √ Flies √ Ticks √ Lice √ Mites

Warning: When using MLs to target a particular parasite, be aware that they will also treat any other of the parasites mentioned above that are present. You can increase the development of pesticide resistance to all of these parasites each time you use an ML product, including non-target parasites.

Note:  √ Can kill dung beetles

How can they be administered?

A variety of application methods for administering pesticide products to cattle are in use.

√ Oral √ Pour-on √ Injection

  • Pour-on formulations have greater variability in absorption than oral or injection formulations.
  • Regardless of how they are administered effective levels of MLs will reach the gastro-intestinal system, lungs, and skin.
  • Note when applied via oral or injection, MLs are not effective against biting lice.


Reported in: √ Worms √ Ticks (found overseas, so far not in Australia)

What is resistance?


Everyone working in the rural industry has a ‘duty of care’; a legal obligation to provide a safe workplace for everyone on the property.

  • Generally, MLs have a wide margin of safety to mammals.


Withholding periods are mandatory with all registered veterinary products used to treat animals for internal and external parasites.

  • Always check the product label before use for specific withholding periods (WHP) and export slaughter interval (ESI) periods. Current ESI periods can be confirmed on the APVMA website.

Types of macrocyclic lactone

A guide to the different chemical actives and the pests they affect are in Table 1. See the Products Search Guides for FlyBossLiceBoss, WormBoss and TickBoss for the appropriate formulation and application method for your target pest. Note that combinations and mixtures of actives may improve treatment efficacy.

Table 1. Macrocyclic lactones, their actives, combinations and mixtures and a summary of the targeted parasites for which formulations are registered. Boxed check marks indicate the pest targeted by multiple actives.

Chemical Pests targeted (may vary with formulation)
Worms Flies Cattle tick Lice Mites
Round worm Intestinal tapeworm Liver fluke Buffalo fly Stable fly
Combination (all actives target boxed parasite)
Abamectin and levamisol
Ivermectin and fluazuron
Moxidectin and levamisole
Abamectin, levamisole and oxfendazole
Mixtures (multiple targets)
Macrocyclic lactone and triclabendazole
Ivermectin and clorsulon
Mixtures and combinations (multiple targets, primary target of actives boxed)
Ivermectin, nitroxinil and clorsulon

What are they?

Macrocyclic lactones are products or chemical derivatives of soil microorganisms belonging to the genus Streptomyces.

How do they work?

MLs have a potent, broad antiparasitic spectrum at low dose levels.

MLs are fast-acting compounds that block nerve transmission in many parasites but have little effect in mammals. They bind to glutamate-gated chloride channel receptors in nerve cells. The resultant sustained channel opening allows influx of chloride ions and paralysis of the parasite neuromuscular system. This reduces the motor capacity of nematodes and causes paralysis, eventually resulting in de-attachment and expulsion from the animal.

MLs become extensively distributed throughout the body and concentrate particularly in fatty tissue. The route of administration and formulation may affect drug absorption, distribution, metabolism, and excretion.

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