Keep sheep parasites at bay

Page last updated: Wednesday, 21 March 2018 - 11:15am

Please note: This content may be out of date and is currently under review.

When you have farm animals, unfortunately worms, lice and flies are sure to follow. Insect pest and parasite infestations will make members of your flock unwell and even cost them their lives. Regular monitoring of animals is essential. This will ensure the early detection and the subsequent effective management of common pests.

If you have yet to buy your sheep, you should carefully consider the breed of sheep and why you want to get them. In Australia there is a wide variety of sheep breeds currently produced.

Different breeds are bred for specific reasons; shedding sheep like Wiltshire Horn and hairy sheep like Dorpers are bred for meat production and usually require no shearing or crutching. Merino sheep on the other hand produce thick woollen coats which require routine shearing and crutching.

Before you bring any livestock onto your property give them a good look over. If there are any signs of scouring, pulled wool or general unwell symptoms, consider getting your vet to give them a check up. This might save problems further down the track with poor performers.

It is also very important to quarantine any new animals brought onto your property. New animals should be kept in a quarantine area to ensure that they are not carrying any parasites which can be passed onto your existing stock. This also allows foreign weed seeds to be excreted in this area rather than spread all over your farm.


Flystrike is the insect pest condition that everyone associates with sheep. It is a painful condition that, if not treated promptly, can result in death.

Flystrike is caused by blowflies which are attracted to smelly, warm, moist environments such as faeces build ups (dags); sweaty, moist skin folds; or open wounds.

Animals will often become flystruck around their anus, although this is not the only region prone to flystrike. Rams can become flystruck in between their horns or on their pizzle.

Flies are more abundant during humid times of the year.

Flystrike is caused when adult blowflies lay eggs on the skin of the sheep, which hatch into maggots. The maggots feed on the sheep’s flesh while they grow, before they drop to the ground and pupate, to hatch eventually into adult flies and begin the process again.

While the maggots are living on the sheep, it develops from being extremely irritating to painful, and sheep can die through shock or infection if the condition is allowed to persist for a number of days.

Once sheep are infested you will need to shear the affected area and expose the maggots. You will then need to treat with one, or more, chemical application(s) to kill the maggots, and disinfect the wounds.

Prevention is far kinder than cure and needs to be part of your normal management routine.

People who own Merino and other long wool sheep should implement tailing and crutching of their stock. Tailing and crutching of animals reduces the amount of wool in the anus region, resulting in less area for dags to form.

You can apply chemicals to repel the flies and keep incidents of flystrike to a minimum. Even after the use of chemicals, it is still necessary to regularly monitor sheep at risk. Treat individually affected sheep, as the effectiveness of chemicals will reduce over time.

Details of current chemical treatments are available from Managing flystrike in sheep, or the FlyBoss website.

Hairy sheep such as the Dorpers or shedding sheep such as the Wiltshire breeds are less likely to be affected but can have some problems and will need monitoring. One or more flystruck sheep in a flock indicates that there are likely to be more incidents.

All sheep need to be observed at least every two days and affected sheep should be treated immediately.

If an animal cannot stand unassisted due to the severity of flystrike injuries, it should be examined by a vet or humanely destroyed.

Animals which have died, or had to be destroyed, need to be deep buried to prevent access by scavenging animals and the development of fly larvae.