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Parasites that infest cattle, sheep and goats include internal parasites, such as worms, flukes and protozoa, and external parasites, such as flies, ticks, lice and mites.

Of the endemic diseases that affect livestock in Australia, parasitic diseases have the largest financial impact on farm productivity.

A recent MLA project that assessed the financial impact of endemic diseases on farm productivity found that five of the eight highest cost diseases of cattle and sheep are caused by parasites (worms, flystrike and lice in sheep and cattle tick and buffalo fly in cattle).

Important considerations in the management of parasites in livestock are:

  • Identification
  • Control
  • Chemical resistance and residues

Impact on animal health and welfare

Parasites can have a negative impact on the health and welfare of animals:

  • Some parasites cause blood loss which, if substantial, can lead to anaemia and death.
  • Other parasites cause diarrhoea which, if severe, can lead to death.
  • Infestation with parasites can reduce the appetite of animals, resulting in debilitated animals that are more susceptible to other diseases.
  • Parasites can also act as vectors, transferring diseases from one animal to another.
  • External parasites like flies cause open sores on the skin of livestock.
  • Flies can also annoy animals, causing them to reduce grazing behaviour or, in severe fly waves, become very agitated (fly worry).

Impact on livestock productivity

These harmful effects can have a negative effect on the productivity of livestock by:

  • Reducing growth rates.
  • Reducing reproductive rates.
  • Causing condemnation of carcase parts at slaughter.
  • Reducing milk production.
  • Reducing fleece weight, fibre diameter and staple strength.
  • Damaging hides and fleeces.

Parasites of livestock can also be zoonoses, meaning humans can become infected as well eg hydatid tapeworm found in sheep and dogs.

Some parasites of cattle, sheep and goats are not found in Australia, for example screwworm fly and some types of mites. It is important to keep these parasites out of Australia, industry biosecurity helps ensure this.

Parasite problems and floods

Following flood events (or significant amounts of rain), the populations of biting insects (buffalo fly, midges, mosquitoes and stable fly) and ticks can increase dramatically.

Producers need to be aware of this and implement proper control measures to prevent animal welfare issues and losses in productivity.

More information on parasite problems in animals after floods can be found on the QLD Primary industries and fisheries website