Lungworm in Cows: Coughing, Breathing Trouble, and Treatment
- Lungworm in cows is usually caused by the parasite *Dictyocaulus viviparus*, which irritates and blocks the airways.
- Common signs include frequent coughing, faster breathing, reduced exercise tolerance, and open-mouth breathing in more severe cases.
- See your vet promptly if a cow is breathing hard, stretching the neck, or the whole group starts coughing on pasture.
- Diagnosis often combines herd history, pasture exposure, clinical signs, and fecal testing for larvae with a Baermann test.
- Treatment usually involves a dewormer chosen by your vet, and some cows also need anti-inflammatory care, antibiotics for secondary pneumonia, or hospitalization-level support.
What Is Lungworm in Cows?
Lungworm in cows is a parasitic disease of the lower airways, most often caused by Dictyocaulus viviparus. The worms live in the bronchi and smaller air passages, where they trigger inflammation, mucus production, and coughing. In heavier infections, the airways can become so irritated that breathing becomes difficult.
This disease is often called "husk" in cattle. It is seen most often in grazing animals, especially calves and youngstock in their first grazing season, but adults can get sick too if their immunity is weak or if they have not had recent exposure. Bought-in cattle and animals moved onto contaminated pasture can also be at risk.
Some cows show mild coughing at first. Others can worsen quickly, especially if there is a heavy parasite burden or secondary bacterial pneumonia develops. That is why a coughing cow on pasture should not be brushed off as a minor issue. Your vet can help sort out whether lungworm, pneumonia, or another respiratory problem is most likely.
Symptoms of Lungworm in Cows
- Frequent dry or harsh coughing
- Faster breathing rate at rest
- Breathing harder after moving or handling
- Reduced grazing, poor weight gain, or drop in milk production
- Nasal discharge or moist cough if secondary infection develops
- Open-mouth breathing, neck extension, or obvious distress
- Weakness, collapse, or sudden death in severe outbreaks
Mild coughing in a few grazing cattle can be the first clue, but worsening breathing effort is the sign that matters most. See your vet immediately if a cow is open-mouth breathing, standing with the neck stretched out, or struggling after only light movement. Herd-level coughing, especially in first-season grazers, also deserves prompt attention because lungworm can spread through contaminated pasture and severe cases may develop secondary pneumonia.
What Causes Lungworm in Cows?
Lungworm disease starts when cattle eat infective larvae while grazing contaminated pasture. After being swallowed, the larvae migrate through the body and eventually reach the lungs, where they mature into adult worms. The adults lay eggs that hatch into larvae, which are coughed up, swallowed, and passed in manure, continuing the cycle on pasture.
Outbreaks are most common in grazing cattle because pasture contamination is central to transmission. First-season grazers are usually the most vulnerable, but adult cows can also become ill if they have little protective immunity. This can happen in animals with limited prior exposure, cattle brought in from another farm, or herds where parasite control has reduced natural exposure enough that immunity is incomplete.
Weather, stocking density, pasture history, and grazing management all affect risk. Lungworm can be unpredictable from year to year, so a farm with little recent trouble can still have a significant outbreak. Your vet will also consider other causes of coughing and breathing trouble, including viral or bacterial pneumonia and noninfectious pasture-associated lung disease.
How Is Lungworm in Cows Diagnosed?
Your vet usually starts with the pattern of disease in the group. Coughing cattle on pasture, especially young animals in the grazing season, raise suspicion for lungworm right away. A physical exam helps assess breathing effort, lung sounds, fever, dehydration, and whether secondary pneumonia may also be present.
Fecal testing is often part of the workup. The Baermann technique is the standard test for detecting lungworm larvae in manure. That said, a negative result does not always rule lungworm out. Larval shedding can be intermittent, and cattle in some stages of infection may test negative even when lungworm is still the problem.
In some herds, your vet may also use antibody testing on serum or bulk tank milk, or recommend postmortem examination if an animal dies. Diagnosis is often a combination of history, season, pasture exposure, clinical signs, and test results rather than a single perfect test. Your vet may also rule out bacterial pneumonia, viral respiratory disease, and toxic pasture-related lung conditions.
Treatment Options for Lungworm in Cows
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or herd-level consultation with your vet
- Targeted deworming plan for affected or exposed cattle
- Common options your vet may consider include ivermectin, doramectin, moxidectin, eprinomectin, fenbendazole, albendazole, or oxfendazole
- Move cattle off heavily contaminated pasture if practical
- Close monitoring of breathing effort, appetite, and response over 24-72 hours
Recommended Standard Treatment
- Veterinary exam plus fecal Baermann testing or other herd diagnostics
- Dewormer selected by your vet based on age, production status, withdrawal times, and herd history
- Anti-inflammatory treatment when indicated to reduce airway inflammation
- Antibiotics if your vet suspects secondary bacterial pneumonia
- Recheck plan for nonresponders and guidance for the rest of the group
Advanced / Critical Care
- Urgent veterinary assessment for severe breathing trouble
- More intensive supportive care such as oxygen access where available, fluids, and repeated monitoring
- Treatment for secondary pneumonia or severe inflammation as directed by your vet
- Additional diagnostics or necropsy on herd mates if the diagnosis is unclear
- Detailed herd outbreak plan covering treatment, pasture risk, and follow-up prevention
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Lungworm in Cows
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look most consistent with lungworm, pneumonia, or another cause of breathing trouble?
- Which cattle in the group should be treated right now, and should exposed herd mates be treated too?
- Which dewormer makes the most sense for these cattle based on age, milk status, and meat or milk withdrawal times?
- Do we need fecal Baermann testing, serum testing, or bulk tank milk testing on this farm?
- Is there evidence of secondary bacterial pneumonia that changes the treatment plan?
- Should these cattle be moved off this pasture, and when is it safe to return?
- What signs mean a cow needs urgent recheck or emergency care?
- What prevention plan makes sense for next grazing season on this farm?
How to Prevent Lungworm in Cows
Prevention starts with knowing your farm's risk. Lungworm is mainly a pasture-acquired disease, so first-season grazers, bought-in cattle, and animals with uncertain immunity deserve extra attention. Work with your vet before turnout to build a parasite plan that fits your herd, grazing system, and local history.
Pasture management can help, but it is not always enough on its own because lungworm outbreaks are unpredictable. Rotational grazing, avoiding heavily contaminated fields for high-risk groups, and paying attention to coughing in the herd can all reduce risk. If a pasture has been linked to a clinical outbreak, your vet may advise keeping susceptible cattle off that ground for the rest of the season.
Strategic deworming may be part of prevention, but timing matters. Overusing dewormers can complicate immunity patterns and broader parasite control goals, so herd plans should be individualized. In some countries, oral vaccination is used on farms with a history of lungworm, but product availability varies by region and may not be an option in the United States. The most practical prevention step for many US herds is early recognition, prompt veterinary guidance, and a season-by-season grazing and parasite control plan.