Worms in Sheep and Goats: What Every Owner Should Know

Internal worms are a common health challenge for sheep and goats, particularly in Queensland. Heavy worm burdens can cause poor growth, weight loss, diarrhoea, anaemia and, in severe cases, death. 

One of the most important worms affecting sheep and goats in Queensland is barber's pole worm (Haemonchus contortus). This blood-feeding parasite can become a serious problem when environmental conditions favour the development of worm larvae on pasture. 

Fortunately, good worm management involves much more than simply giving your animals a drench.

Worm eggs are passed in an animal's faeces. Under suitable conditions, these eggs develop into infective larvae on the pasture.

When sheep or goats graze, they can ingest these larvae, allowing the worms to develop inside the animal and produce more eggs.

Warm and moist conditions can allow worm larvae to develop and survive on pasture, increasing the risk of infection. This is particularly important in Queensland, where summer rainfall can create favourable conditions for barber's pole worm.

The risk isn't the same all year or on every property, however. Weather, pasture conditions, stocking rates, animal age and the history of worm control on the property all influence the risk.

Barber's pole worm is one of the most important internal parasites of sheep and goats in Queensland.

Unlike many other worms, barber's pole worm feeds on blood. Heavy infections can therefore cause significant blood loss and anaemia.

Signs can include:

• Pale gums or the inside of the eyelids
• Weakness or lethargy
• Poor growth or weight loss
• Reduced appetite
• A rough coat or fleece
• Swelling underneath the jaw, known as bottle jaw
• Animals separating from or lagging behind the mob
• Sudden illness or death in severe cases

Barber's pole worm can affect animals of all ages and can become particularly dangerous when worm burdens increase rapidly.

Other worms can also affect sheep and goats and may cause problems such as diarrhoea, poor growth and loss of condition.

Importantly, not every animal with diarrhoea or weight loss has worms. Other parasites, nutritional problems and diseases can cause similar signs.

Regular observation is an important part of worm management.

Look for changes in your animals':

• Body condition
• Growth and weight gain
• Energy levels
• Coat or fleece
• Faeces
• Gum and eyelid colour
• Overall behaviour

Bottle jaw and pale eyelids can be warning signs of significant parasite problems, particularly barber's pole worm.

However, waiting until animals are visibly sick isn't the best way to manage worms. By this stage, animals may already have experienced production losses and, in the case of barber's pole worm, severe anaemia can develop.

This is why testing and regular monitoring are important parts of a worm control program.

A faecal egg count (FEC) is a test performed on faeces to estimate the level of worm infection in a group of animals.

Regular testing can help determine:

• Whether worm burdens are increasing
• Whether treatment is required
• Which types of worms may be present when combined with larval culture
• Whether a drench has worked effectively

WormBoss recommends using regional guidelines when interpreting worm egg counts because the appropriate treatment threshold can vary according to the worms present, region and circumstances.

For properties with ongoing worm problems, your veterinarian can help determine an appropriate testing schedule.

This is one of the most important changes in modern worm management.

Drench resistance is a growing problem in Australian sheep and goat production.

When animals are repeatedly treated with drenches, worms that survive the treatment can reproduce. Over time, a greater proportion of the worm population can become resistant to that drench.

This means a product that once worked well may eventually become less effective — or stop working altogether.

Unnecessary drenching, incorrect dosing and relying heavily on persistent drenches can all contribute to the development of resistance.

The aim of modern worm control is therefore not to eliminate every worm from every animal.

Instead, we want to keep worm burdens low enough to protect animal health and productivity while preserving the effectiveness of the drenches available to us.

You may hear your veterinarian or worm control advisor talk about refugia.

Refugia refers to worms and worm larvae that have not been exposed to a drench.

Maintaining some susceptible worms in the population can help dilute worms that have survived treatment and are resistant to the drench.

This is one reason blanket drenching of every animal, every time, isn't always the best approach.

However, refugia strategies need to be used appropriately and are not suitable for every animal or situation. They should form part of an overall worm management plan rather than being applied automatically.

Good worm control is a combination of pasture management, animal management, testing and appropriate treatment.

Manage your pasture

Worm larvae are picked up while animals graze, so pasture management can influence how many larvae animals consume.

Where practical:

• Avoid grazing pasture excessively short.
• Maintain adequate pasture cover.
• Avoid unnecessarily high stocking rates.
• Consider how and when different mobs use paddocks.
• Plan low-worm-risk paddocks for particularly susceptible animals.

Good pasture management can reduce exposure to infective larvae and complement other worm control measures.

Pay particular attention to high-risk animals

Young animals and females around late pregnancy and lactation can be more susceptible to the effects of worms.

Good nutrition is also important. Animals that are well nourished and maintaining good body condition are better able to cope with parasite challenges.

When an animal or mob needs treatment, choosing an effective drench is important.

Not all drenches work equally well on every property. Worm populations can develop resistance to particular drench groups, so the effectiveness of a product should not simply be assumed.

WormBoss recommends using drenches known to be effective on the property and, where appropriate, using combinations of effective drench groups to help slow the development of resistance. Short-acting treatments are generally preferred, with persistent products reserved for particular circumstances.

When drenching:

• Use the correct product for the species.
• Weigh animals where possible.
• Dose according to the heaviest animals being treated.
• Make sure drenching equipment is correctly calibrated.
• Follow the product label.
• Observe meat withholding periods and other relevant restrictions.
• Don't assume that changing between drenches automatically prevents resistance.

Your veterinarian can help determine which treatment is appropriate for your animals and situation.

It's particularly important to remember that goats are not simply small sheep when it comes to worm control.

Goats can metabolise some drenches differently from sheep, and some products or dose rates used in sheep aren't appropriate for goats.

For this reason, don't automatically use a sheep worming product or sheep dose on your goats without veterinary advice.

WormBoss also provides separate worm control programs and recommendations for sheep and goats, including region-specific advice.

If you have been using the same drench for some time, it is worth finding out whether it is still working effectively on your property.

A DrenchCheck can compare worm egg counts before and after treatment to provide an indication of how effectively a drench has reduced the worm burden.

More comprehensive testing can be used when drench resistance is suspected.

Knowing what actually works on your property is much more useful than simply changing drenches every year.

There isn't one worming schedule that works for every flock or herd.

A good program considers:

Your animals + your pasture + your local weather conditions + worm egg counts + previous drench use + drench effectiveness

Rather than automatically drenching the whole flock or herd, your veterinarian can help you develop a plan for monitoring worm burdens and treating animals when treatment is actually needed.

This approach can help protect your animals while also slowing the development of drench resistance.

Contact Vet Cross if your sheep or goats are:

• Losing weight or condition
• Not growing as expected
• Scouring
• Weak or lethargic
• Showing pale gums or eyelids
• Developing swelling under the jaw
• Suddenly becoming unwell
• Not responding as expected to a worming treatment

We can also discuss faecal egg counts, drench effectiveness and developing a worm management program for your property.

Don't wait until your animals are seriously affected by worms. Early monitoring can make worm control much easier.

Sources & Further Information

• WormBoss - information and resources on worm control in sheep and goats
• Queensland Government - sheep and goat worm management
• Australian Small Ruminant Association / relevant veterinary resources

Written by: Vet Cross marketing team

Clinically reviewed by: Dr Amy Cox BVSc (hons)

Last reviewed: October 2026