Lungworm in Sheep: Symptoms, Treatment and Prevention

Quick Answer
  • Lungworm in sheep is a parasitic infection of the airways and lungs, most often linked to *Dictyocaulus filaria*, though other lungworms can affect sheep too.
  • Common signs include coughing, faster breathing, reduced stamina, poor weight gain, and in heavier infections, open-mouth breathing or pneumonia-like illness.
  • Your vet usually confirms lungworm with a fresh fecal Baermann test, flock history, and a physical exam. Chest imaging or necropsy may be used in unclear cases.
  • Treatment often includes a prescription dewormer chosen by your vet, plus supportive care when breathing is affected or secondary pneumonia is suspected.
  • Typical U.S. cost range for exam plus fecal testing and treatment planning is about $150-$450 per visit, with higher costs if multiple sheep are affected or hospital-level care is needed.
Estimated cost: $150–$450

What Is Lungworm in Sheep?

Lungworm is a parasitic infection that affects the breathing passages and lung tissue of sheep. The most important species is Dictyocaulus filaria, although Muellerius capillaris and Protostrongylus rufescens can also be involved. These parasites irritate the airways, trigger inflammation, and can make sheep cough or breathe harder than normal.

Some sheep carry light infections with few obvious signs. Others, especially lambs or animals under stress, can develop noticeable respiratory disease, poor growth, and reduced flock performance. In more serious cases, lungworm can look a lot like bacterial pneumonia, which is one reason a veterinary exam matters.

Lungworm is usually picked up on pasture. Infective larvae are swallowed while grazing, then migrate through the body and mature in the lungs. Warm, moist conditions tend to support parasite survival, so risk often rises when pasture contamination and stocking pressure increase.

Because coughing in sheep has several possible causes, including pneumonia, dust irritation, and other parasites, it is best to have your vet sort out the cause before treatment decisions are made.

Symptoms of Lungworm in Sheep

  • Dry or moist cough, especially after moving or handling
  • Faster breathing or increased effort at rest
  • Reduced exercise tolerance, lagging behind the flock
  • Poor weight gain, weight loss, or thriftiness
  • Nasal discharge or noisy breathing
  • Open-mouth breathing, marked distress, or weakness
  • Sudden decline when secondary pneumonia develops

A mild cough in one sheep may not look dramatic, but repeated coughing across a group deserves attention. Lungworm can reduce growth and condition before severe breathing signs appear.

See your vet immediately if a sheep is breathing with obvious effort, stretching its neck, breathing with its mouth open, acting depressed, or refusing feed. Those signs can mean advanced lung disease, pneumonia, or another emergency that needs prompt care.

What Causes Lungworm in Sheep?

Lungworm is caused by parasitic nematodes that complete part of their life cycle in or around the respiratory tract. In sheep, Dictyocaulus filaria has a direct life cycle, meaning sheep become infected by grazing infective larvae from contaminated pasture. Other lungworms, such as Muellerius and Protostrongylus, use snails or slugs as intermediate hosts.

Pasture conditions matter. Warmth, moisture, and close grazing pressure help larvae survive and spread. Young sheep are often more vulnerable because they have less immunity, but adults can still be affected, especially if parasite pressure is high or nutrition and overall flock health are not ideal.

Lungworm problems can also overlap with other parasite burdens. Sheep with gastrointestinal worms may have poorer body condition and less resilience, making respiratory signs more noticeable. New additions to the flock can introduce parasites as well, which is why quarantine and a flock parasite plan are important.

Not every coughing sheep has lungworm. Bacterial pneumonia, viral disease, dust, and environmental stress can cause similar signs, so your vet may need to rule out several possibilities.

How Is Lungworm in Sheep Diagnosed?

Your vet will start with the flock history, season, pasture conditions, age group affected, and the pattern of coughing or breathing changes. A physical exam helps assess how serious the respiratory signs are and whether pneumonia or another condition may also be present.

The most useful routine test is a fresh fecal Baermann exam, which looks for lungworm larvae rather than standard parasite eggs. Sample handling matters. Fresh feces collected directly from the sheep and processed promptly give the best chance of finding larvae. In some cases, your vet may also recommend a fecal egg count for other parasites, because mixed parasite burdens are common.

If the diagnosis is still unclear, your vet may consider additional options such as tracheal wash or bronchial sampling, imaging, or postmortem examination of a sheep that has died. These steps can help distinguish lungworm from bacterial pneumonia, chronic lung damage, or other respiratory disease.

A negative test does not always rule lungworm out, especially early in infection or if samples are old or poorly handled. That is why your vet will interpret test results together with clinical signs and flock risk factors.

Treatment Options for Lungworm in Sheep

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$150–$300
Best for: Mild to moderate coughing sheep that are still eating, standing, and breathing without major distress.
  • Farm or clinic exam for one sheep or a small group
  • Fresh fecal Baermann testing through a veterinary clinic or diagnostic lab
  • Prescription dewormer selected by your vet based on likely parasites, label use, and local resistance concerns
  • Basic nursing care such as reducing stress, easy access to water, and moving affected sheep to a dry, low-stress area
Expected outcome: Often good when treated early and when lung damage is limited.
Consider: This approach keeps testing and treatment focused, but it may miss secondary pneumonia, severe inflammation, or broader flock issues if signs worsen.
Most Common

Recommended Standard Treatment

$300–$800
Best for: Most flock situations with persistent coughing, reduced growth, multiple affected sheep, or concern for mixed parasite disease.
  • Veterinary exam plus fecal Baermann and often fecal egg count for other internal parasites
  • Prescription deworming plan for affected sheep and, when appropriate, a flock-level strategy
  • Assessment for concurrent bacterial pneumonia or dehydration
  • Supportive medications or antimicrobials when your vet believes secondary infection or significant airway inflammation is present
  • Follow-up recheck or repeat fecal testing to confirm response
Expected outcome: Good to fair, depending on parasite burden, age of the sheep, and whether pneumonia or chronic scarring is already present.
Consider: Costs more up front, but it gives a clearer diagnosis and a more complete flock plan. Medication withdrawal times and resistance concerns must be reviewed carefully with your vet.

Advanced / Critical Care

$800–$2,000
Best for: Sheep with open-mouth breathing, collapse, marked weakness, suspected pneumonia, or outbreaks causing major flock losses.
  • Urgent veterinary assessment for severe breathing difficulty
  • Expanded diagnostics such as bloodwork, imaging, airway sampling, or necropsy of a flockmate when needed
  • Intensive supportive care, which may include fluids, oxygen support where available, and close monitoring
  • Targeted treatment for severe secondary pneumonia or complications
  • Detailed flock investigation covering pasture management, quarantine practices, and parasite-control failures
Expected outcome: Guarded to fair in severe cases. Some sheep recover, but chronic lung scarring can limit long-term performance.
Consider: This tier offers the most information and support, but it is more resource-intensive and may not change the outcome if lung damage is already advanced.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Lungworm in Sheep

Bring these questions to your vet appointment to get the most out of your visit.

  1. Does this look more like lungworm, pneumonia, or both?
  2. Which fecal test do you recommend, and how fresh should the sample be?
  3. Should we test one sheep or several from the flock?
  4. Which dewormer options fit our flock, and what resistance concerns matter in our area?
  5. Do any treated sheep need special monitoring for breathing trouble after treatment?
  6. Are there meat or milk withdrawal times I need to follow?
  7. Should we change pasture rotation, stocking density, or quarantine steps to lower reinfection risk?
  8. When should we recheck feces or re-examine the flock to make sure the plan worked?

How to Prevent Lungworm in Sheep

Prevention starts with flock-level parasite management. Work with your vet to build a plan that fits your region, pasture conditions, and resistance risks. That usually means using dewormers thoughtfully, avoiding unnecessary whole-flock treatment when not indicated, and checking parasite burdens with fecal testing rather than guessing.

Pasture management also matters. Rotating grazing areas, avoiding overstocking, and reducing prolonged exposure to wet, heavily contaminated ground can help lower parasite pressure. Quarantining new sheep and reviewing their parasite status before they join the flock can reduce the chance of bringing in new worms or resistant parasites.

Good nutrition and low-stress handling support resilience. Lambs, thin sheep, and animals dealing with other disease challenges may show more severe signs when parasite pressure rises. Watching for early coughing, poor growth, or lagging animals can help your vet intervene before the problem spreads.

There is no widely used sheep lungworm vaccine in U.S. practice, so prevention relies mainly on monitoring, pasture hygiene, quarantine, and a veterinary-guided parasite-control program.

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