Lungworm Infection in Pigs

Lungworm infection in pigs is a parasitic disease most often caused by Metastrongylus species, including M. apri and M. pudendotectus. These worms live in the bronchi and smaller airways, where they irritate lung tissue and can trigger coughing, airway inflammation, and reduced breathing efficiency.

The parasite has an indirect life cycle. Eggs are coughed up, swallowed, and passed in manure. Earthworms then act as the intermediate host, and pigs become infected when they root and eat those infected earthworms. Because of that, lungworm is seen more often in pigs with outdoor soil access than in pigs raised in well-managed indoor systems.

Some pigs have mild signs, especially early on. Others develop a harsh cough, poor weight gain, exercise intolerance, or pneumonia-like illness. Young pigs and pigs with other respiratory problems can be affected more noticeably. If your pig is coughing or breathing harder than normal, your vet can help sort out whether parasites, infection, environment, or more than one issue is involved.

The direct cause is infection with Metastrongylus lungworms. Unlike many intestinal parasites, these worms need an intermediate host to complete their life cycle. Earthworms pick up the eggs from contaminated manure, the larvae develop inside the earthworm, and pigs become infected when they eat those earthworms while rooting.

That means risk is tied closely to environment and management. Pasture-raised pigs, backyard pigs with soil access, and pigs kept on ground that has housed infected pigs before are more likely to be exposed. Wild pigs and feral swine can also help maintain parasite pressure in some areas.

Not every exposed pig gets equally sick. Younger pigs, pigs under stress, and pigs with concurrent bacterial or viral respiratory disease may show more obvious illness. Heavy parasite burdens can also make secondary pneumonia more likely, which is one reason a cough in pigs should not be brushed off.

Your vet will usually start with history and exam findings. Important clues include outdoor access, rooting behavior, coughing in multiple pigs, poor growth, and whether the problem is seasonal or recurring on the same ground.

Fecal testing is often part of the workup. Depending on the stage of infection and the lab used, your vet may recommend fecal flotation, sedimentation, or a Baermann-type test to look for parasite eggs or larvae. In herd situations, your vet may also suggest testing several pigs rather than only one animal.

If signs are more severe, your vet may also evaluate for bacterial pneumonia, swine influenza, PRRS, roundworm migration, or environmental causes such as dust and ammonia. In some cases, lungworms are confirmed at necropsy, where adult worms may be found in the bronchi. Because coughing in pigs has several possible causes, diagnosis works best when parasite testing is paired with a full clinical picture.

Prevention focuses on reducing exposure and lowering parasite pressure over time. Because pigs usually get lungworm by eating infected earthworms, outdoor systems need especially thoughtful management. Rotating ground, avoiding overcrowding, and limiting buildup of manure in high-traffic areas can help reduce exposure.

Good herd health matters too. Pigs under nutritional stress or dealing with other respiratory disease may be more affected by parasites. Quarantining new arrivals, reviewing deworming history, and working with your vet on a parasite-control plan can help protect both pet pigs and small production groups.

Routine deworming should be tailored to the pig's environment, age, and local parasite pressure rather than done blindly. In some settings, your vet may recommend strategic fecal monitoring and treatment at key times, especially for pigs with pasture access. If coughing keeps coming back, ask your vet to reassess both the parasite plan and the housing setup.