Mycoplasmal Pneumonia in Pigs: Enzootic Pneumonia Symptoms and Control

Mycoplasmal pneumonia, also called enzootic pneumonia, is a chronic respiratory disease of pigs most often caused by Mycoplasma hyopneumoniae. It is one of the most important bacterial respiratory diseases in swine and is found worldwide. In many herds, the disease is mild on the surface but still causes meaningful production losses through coughing, reduced average daily gain, and more days to market.

A classic pattern is a persistent dry cough in growing pigs, especially when they are stirred up or moved. Mortality is often low in endemic herds, but the infection damages the respiratory tract and can make pigs more vulnerable to other respiratory pathogens. That is one reason enzootic pneumonia is often discussed as part of the broader porcine respiratory disease complex.

This condition can also be subclinical, meaning pigs may not look dramatically sick even while lung lesions are developing. At slaughter or necropsy, affected lungs often show cranioventral consolidation, especially in the apical and cardiac lobes. Because of that, herd monitoring matters even when signs seem mild.

If you are caring for pet pigs, small farm pigs, or a backyard herd, it helps to think of this as a management-sensitive disease. Treatment can help, but long-term control usually depends on a combination of veterinary guidance, housing improvements, pig flow, and vaccination planning.

The main cause is infection with Mycoplasma hyopneumoniae, a bacterium that spreads primarily through close pig-to-pig contact and respiratory secretions. Coughing helps move the organism through a group, and infected pigs can keep transmitting it for extended periods. In herd settings, replacement animals, mixing age groups, and movement of pigs between sites can all contribute to spread.

This organism targets the cilia that help clear the airways. When those defenses are damaged, the lungs become more vulnerable to other pathogens. That is why mycoplasmal pneumonia often becomes more severe when pigs are also dealing with viruses such as PRRS or swine influenza, or with secondary bacterial infections.

Environmental and management stressors matter a great deal. Poor ventilation, crowding, temperature swings, dust, ammonia buildup, and inconsistent pig flow can all increase disease pressure. Season, transport, regrouping, and other stress events may trigger more obvious coughing or respiratory flare-ups.

In practical terms, enzootic pneumonia is rarely only about the bacterium itself. It is usually the result of pathogen exposure plus herd conditions. Your vet can help sort out which factors are driving disease on your farm or in your pig group.

Diagnosis usually starts with the pattern of disease in the group. Your vet will look at age affected, duration of coughing, growth performance, housing conditions, and whether other respiratory pathogens may be involved. Clinical signs and herd history are often strongly suggestive, but confirmation is important because several swine respiratory diseases can overlap.

PCR testing is now the most commonly used confirmation tool. Samples may include nasal, laryngeal, tracheal, or bronchial swabs, oral fluids, and lung tissue. In live pigs, tests are generally more sensitive when samples come from closer to the lower respiratory tract. When necropsy is available, bronchial swabs or lung tissue that includes airways can improve detection.

Serology can be used at the herd level, but it has limits. Antibody tests may be harder to interpret because pigs can seroconvert slowly, and vaccination can complicate results. Culture is not commonly used in routine practice because M. hyopneumoniae is difficult to grow.

For pet parents and small producers, the most useful next step is often to ask your vet which pigs should be sampled and whether a necropsy, if a pig dies, would give the clearest answer. A single test may not tell the whole story, so diagnosis often works best as a herd-level plan rather than a one-pig snapshot.

Prevention works best when it combines biosecurity, pig flow, air quality, and vaccination. Good ventilation, appropriate space allowance, lower dust and ammonia exposure, and reduced mixing of age groups can all lower disease pressure. In many systems, all-in/all-out management is one of the most effective ways to reduce lung lesions and improve growth performance.

Vaccination is a useful control tool, but it has limits. Current commercial inactivated vaccines can reduce coughing and lung lesion severity, yet they do not fully prevent infection. That means vaccination is usually part of a broader plan rather than a stand-alone fix.

For breeding herds and larger operations, your vet may discuss replacement gilt acclimation, prefarrowing management, herd closure, or even elimination strategies. University of Minnesota work has highlighted how timing and sample choice matter when monitoring herds, especially if a farm is trying to identify infection status accurately over time.

For pet parents and small producers, the practical prevention steps are straightforward: avoid introducing pigs of unknown health status, quarantine newcomers, keep housing clean and well ventilated, reduce stress, and call your vet early if coughing starts to spread. Early action often costs less than trying to control a well-established respiratory problem later.