Swine Enzootic Pneumonia

Swine Enzootic Pneumonia or ‘Mycoplasma hyopneumoniae’

Swine Enzootic Pneumonia is caused by the bacteria Mycoplasma hyopneumoniae and is one of the biggest contributors to respiratory diseases in pigs.

On its own, in a controlled environment, the bacteria would not cause many problems. However, Mycoplasma hyopneumoniae interacts with other infections or viruses (for example the PRRS virus  to aggravate the pneumonia and cause severe damage to the lining of the lungs.

Transmission of Mycoplasma hyopneumoniae occurs via direct contact with affected pigs. It is transferred from sow to piglet and it typically affects pigs aged six weeks and older.

Signs of Mycoplasma hyopneumoniae infection
The severity of the infection depends on whether there are other infections present. In uncomplicated infections Mycoplasma hyopneumoniae causes:

• Mild, reoccurring pneumonia with a dry cough
• Rough hair coat
• Reduced growth rate and feed efficiency

With secondary bacterial infections clinical signs are more severe:

• Increased coughing
• Laboured breathing
• Elevated temperatures
• Prostration

Diagnosing a Mycoplasma hyopneumoniae infection

Diagnosis is usually based on the following:

• A chronic dry cough
• PCR testing on lung tissue or lung flushes
• ELISA testing – however antibodies may only be present six weeks after infection, so this test is limited
• Historical examination of lung tissue to show inflammation
• Lung lesions at autopsy: lungs are meat-like and purple-grey in colour with lesions, though the Swine Influenza virus can cause similar lesions

Treatment and prevention of Mycoplasma hyopneumoniae infections

Preventing Mycoplasma hyopneumoniae depends on good management. Optimal conditions for pig health and immunity should be prioritised: attention to air quality, ventilation, temperature and stocking density. Age segregation and a strict all-in, all-out policy are also very important.

M + PAC - one or two shot vaccination programme

Antibiotics can be used in the treatment of Mycoplasma hyopneumoniae infections, but timing is difficult. Treating too late or too early is ineffective, so it often needs to be continued over an extended period. Medicated Early Weaning will produce litters free of Mycoplasma hyopneumoniae bacteria.

Understanding the bacteria

The Mycoplasma hyopneumoniae bacteria attach to the cilia (protective lining) in the airways. This causes clumping of cilia, loss of cilia and excessive production of mucus. This damage makes the respiratory tract more susceptible to infection. This is why a Mycoplasma hyopneumoniae infection is often seen in conjunction with other viral infections (frequently PRRS  and PCV2) and bacterial infections (Pasteurella multocida, Bordetella bronchiseptica, Streptococcus suis, Haemophilus parasuis/Glassers disease and Arcanobacterium pyogene) as part of the wider Porcine Respiratory Disease Complex.
Mycoplasma hyopneumoniae also affects the immune response of the pig. It is both immunosuppressive and stimulatory to lymphocytes. The bacteria induce the production of pro-inflammatory cytokines, including IL-1 TNF and IL-6, which are responsible for much of the inflammation and chronic nature of Mycoplasma hyopneumoniae infections.