Prevention, management and control

Parasites are a natural part of the ecology in which cattle, sheep and goats have evolved.

Parasites need a host to survive, so most successful parasites do not commonly kill their host. Instead, there is usually an equilibrium between hosts and parasites and the incidence of disease due to parasite infestation is low.

Human management, production requirements or environmental manipulation alter this equilibrium by preventing migration of animals, increasing population density (stocking rate), and allowing parasites to flourish. Successful and sustainable parasite control can only be achieved when the impact of these factors on parasites is recognised.

Relying on chemical control options alone may produce only short-term results and will probably be unsustainable, partly because of the inevitable emergence of resistance to the chemicals in the parasites.

Principles of parasite control

For the best chance of success, a parasite control program needs to integrate the judicious use of chemicals with grazing management and the exploitation of host factors of resistance and resilience (age, breed, nutritional and physiological status), while taking into account environmental factors.

Parasite control approaches

By the time animals are showing clinical signs of parasite infestation, substantial productivity losses will have already occurred.

To minimise the likelihood of parasite infestation and to avoid the consequential impacts on animal health, animal welfare and productivity, a planned preventative program must be considered and implemented.

With prevention being better than cure, below are some possible approaches to consider.

• Planning as part of a farm animal health or biosecurity plan

This should include planning how to control parasites in livestock already on the farm, as well as options for treating and quarantining introduced livestock prior to releasing them onto the property.

Always request an animal health statement when purchasing livestock to verify the disease status level of assurance that is being provided by the livestock vendor.

• Knowing the parasites that occur in the region

Some parasites are adapted to the tropical and subtropical regions of northern Australia, whereas others occur mainly in the temperate southern regions. Know the parasites that have adapted to your region and have a suitable prevention strategy in place.

• Reducing the parasite challenge

This is particularly important in more intensive production systems in high rainfall regions where substantial numbers of parasites can accumulate on pastures. The Wormboss website has information on preparing low worm-risk paddocks and grazing management to reduce the reinfestation of parasites.

• Improving nutrition

Animals affected by drought or on a low plane of nutrition are more susceptible to parasites.

Parasite levels in these animals must be carefully monitored, especially if environmental conditions favour parasite development.

• Protecting susceptible livestock

Some livestock will be more susceptible to parasites through factors such as genetics, age, status or health and extra protection measures should be implemented for these animals.

Examples of this include having low-worm pastures available for young and pregnant livestock and not introducing tick-naïve animals to tick-infested pastures unless they can be carefully monitored.

• Using breeding to improve parasite control

This includes activities such as using breeds more resistant to cattle ticks in tick-endemic regions or integrating selection for resistance to worms into sheep breeding objectives.

• Monitoring livestock and only using chemicals when required

Some parasite infestations only need to be treated when they reach certain levels. For example, in regions where buffalo fly is a problem for cattle, monitor fly numbers and only treat when there are more than 200 flies per beef animal (100 per side) or more than 30 per dairy animal. Similarly in sheep, worm egg count monitoring determines when drenching is, or isn’t, required.

• Using drenches, pour-ons and other chemicals strategically as part of an overall parasite control program

When using drenches, pour-ons and other chemicals, only apply products registered for use in the livestock being treated.

Read the label thoroughly before use and follow all label directions or restrictions, including directions for dose rates, safety precautions, personal protective equipment, withholding periods (WHPs), export slaughter intervals (ESI), re-handling intervals and disposal of empty containers and unused product.

Record the appropriate information and include on the LPA NVD/Waybill if the livestock are sold.