• Delivers the chemical under the skin into the subcutaneous tissues where it enters blood capillaries which deliver it to the site where the parasite resides.
  • Requires a recommended applicator with specialised short needles.
  • Animals should be restrained in a crush.
  • Needles can be used on multiple animals; replace when blunt or damaged.
  • Injection volume is based on the weight of the cattle being treated.
  • Injection site is usually the subcutaneous tissue high on the neck (behind the ear); follow label instructions for each product as they can differ.
  • Follow label instructions for recommended needle gauge (width) and length, as these will vary with the viscosity of the solution and age of the animal (thickness of the skin).


A parasite population can develop resistance to a chemical through:

  • repeated use of the same active.
  • repeated overuse of a chemical (unnecessary treatments).
  • wide-spread under-dosing of a chemical (e.g. under-estimating the weight of animals being treated, poor application technique, uncalibrated dosing).
  • unintentionally exposing non-target parasites to chemicals (e.g. products to treat tick or lice can also affect worms).

What is resistance?


  • Ease of application.
  • Accurate dosing.
  • Efficacy is completely independent of weather conditions and animal behaviour following treatment.


  • May cause adverse reactions at the injection site.
  • May transfer microorganisms between animals.
  • May leave excessive residues at the injection site.
  • May not be approved for use in some classes of stock due to long withholding period (WHP).


  • Low risk of inadvertent chemical exposure If used according to label directions.

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

How it works

Chemicals administered by injection are formulated for introduction under the skin and to be absorbed into the capillary system of the subcutaneous tissues.

Secondary parasite effects

Some broad-spectrum actives, such as macrocyclic lactones, can affect both internal parasites (worms) and external parasites that feed on blood, such as ticks, buffalo flies, stable flies and sucking lice. This unintentional exposure of non-target, secondary parasites to chemical actives can lead to these populations developing resistance.