Lungworms (Respiratory Nematodes)
Lungworms are parasitic roundworms that live in the respiratory system, rather than the digestive tract. They affect a range of grazing animals, including horses, donkeys, cattle, sheep, and goats.
Instead of causing digestive problems, lungworms irritate the airways and lungs, leading to coughing, breathing difficulties, and reduced performance. Because the signs often resemble common respiratory infections or allergies, lungworm infections are frequently overlooked.
Why Lungworms Matter
Lungworms cause inflammation of the airways and lung tissue. This reduces the animal’s ability to breathe efficiently and deliver oxygen to the body.
Over time, this can lead to:
Persistent coughing
Nasal discharge
Increased breathing effort
Reduced exercise tolerance
Lethargy
Weight loss
Poor growth in young animals
Reduced productivity
In severe or untreated cases, lung damage can become long-term.
Lungworms in Different Animals
Equines (Horses & Donkeys)
True lungworm infections are uncommon in horses but do occur, especially in donkeys, which can carry lungworms without showing obvious signs. Horses grazing alongside donkeys are therefore at higher risk.
Affected horses may show:
Chronic coughing
Nasal discharge
Exercise intolerance
Poor performance
Because these signs mimic other respiratory conditions, lungworms are often not considered until other causes have been ruled out.
Livestock (Cattle, Sheep & Goats)
Lungworms are far more significant in livestock.
In cattle, Dictyocaulus viviparus is a major cause of parasitic bronchitis.
In sheep and goats, several lungworm species can infect the airways and lung tissue.
Infected animals may show:
Persistent coughing
Rapid or laboured breathing
Weight loss
Reduced appetite
Poor growth
Weakness
In young or heavily infected animals, lungworms can cause severe respiratory distress and, in extreme cases, death.
How Lungworms Spread
Lungworms have a direct life cycle, closely linked to grazing.
Adult worms in the lungs lay eggs that hatch into larvae. These larvae are coughed up, swallowed, and passed out in the manure. On pasture, they develop into infective stages.
Animals become infected when they graze on contaminated pasture. Once ingested, larvae migrate from the intestine to the lungs, where they mature and begin the cycle again.
Moist, cool grazing conditions allow larvae to survive longer on pasture, increasing infection risk.
Signs of a Lungworm Burden
Lungworm infections usually show up as respiratory signs rather than digestive ones.
Common signs include:
Chronic or persistent coughing
Nasal discharge
Laboured or rapid breathing
Reduced stamina
Lethargy
Weight loss
Poor growth in young animals
Reduced productivity
Because these signs can look like pneumonia, allergies, or viral infections, proper detection is essential.
Detection
Lungworms are not always detected using standard faecal egg counts.
Detection may involve:
Specialised faecal tests for lungworm larvae
Clinical examination
Review of grazing history and exposure risk
Response to targeted treatment
In equines, especially those grazing with donkeys, lungworms should be considered in cases of unexplained chronic coughing.
Treatment & Long-Term Control
Lungworms usually respond well to appropriate antiparasitic treatment, but reinfection can occur if pasture management is not addressed.
Long-term control includes:
Targeted treatment based on detection
Strategic pasture management
Avoiding overstocking
Mixed grazing management
Quarantine and testing of new animals
Regular monitoring
In livestock systems, lungworm control is often closely linked to grazing rotation and stocking density.