Swine Enzootic Pneumonia

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Swine Enzootic Pneumonia

Swine Enzootic Pneumonia: Confluent consolidation of cranioventral lung lobes

Confluent consolidation of cranioventral lung lobes

"Swine Enzootic Pneumonia is one of the most important contributors to respiratory diseases in pigs."

Swine Enzootic Pneumonia is one of the most important contributors to respiratory diseases in pigs.

M. hyopneumoniae interacts with other infections, damaging the cilia and epithelia of the airways of the lower respiratory tract, making way for invasion by secondary pathogens. Viral infection can complicate the picture even further.

Interactions with other pathogens

  • Pasteurella multocida
  • Streptococcus suis
  • Glasser Disease
  • Porcine pleuropneumonia
  • PRRS virus
  • Porcine Circovirus (Associated) Disease (PCVD) type 2 (PCV2)

About M. Hyopneumoniae

  • Pathogenesis
  • Clinical signs
  • Diagnosis
  • Treatment and prevention

  • Pathogenesis

    Transmission of Swine Enzootic Pneumonia occurs via nose-to-nose contact between pigs. Transmission between herds is unlikely due to this organism’s incredibly slow growth and limited ability to survive in the environment. The organism is passed from sow to piglet, but the frequency of pathogen shedding by the sow decreases with increased parity: 73% of parity 1 sows, 50% of parity 6-7 sows, and only 6% of parity 8-11 sows can be found to shed the bacteria. Early weaning at 7-10 days of age can decrease the transmission of pathogen to young suckling piglets. While signs of infection with M. hyopneumoniae are not generally seen in pigs less than 6 weeks of age, any age of pig can become infected with this pathogen. Clinical symptoms of the disease tend to occur in pigs around 2-6 months of age.

    The incubation period is dose-dependent. For high doses, the incubation period is 11 days, and for moderate doses, it is approximately 4-6 weeks. Low doses cause subclinical chronic infections.

    The organism attaches to the cilia in the airways. This causes clumping of cilia, loss of cilia and excessive production of mucous. The mucociliary apparatus is thus impaired, causing reduced clearance of inhaled particles and making the respiratory tract more susceptible to opportunistic infections. M. hyo infection is often found in conjunction with other viral (especially PRRS and PCV2) infections and bacterial infections (P. multocida, B. bronchiseptica, S. suis, H. parasuis, A. pyogenes) as part of PRDC.

    M. hyo also modulates the immune response of the host. It is both immunosuppressive and stimulatory to lymphocytes. M. hyo induces 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 mycoplasmal pneumoniae.


    Clinical signs

    The severity of the clinical signs and the degree of economic loss depend on the agents involved, secondary bacterial and/or viral infections, as well as environmental and management factors.

    In uncomplicated infections, Swine Enzootic Pneumonia causes:

    • Mild chronic pneumonia with a non-productive cough
    • Rough hair coat
    • Reduced growth rate and feed efficiency

    With secondary bacterial infections and/or viral infections, clinical signs are more severe, including:

    • Increased coughing
    • Labored breathing
    • Anorexia
    • Fever
    • Prostration


    Diagnosis of M. hyopneumoniae infection

    Diagnosis is based on:

    • Clinical signs - chronic, non-productive coughing

    • Lung lesions upon necropsy

      1. Lungs are meat-like and purple-grey in color.
      2. Lesions are typically located in the cranio-ventral regions of the lungs, although swine influenza virus and other pathogens can cause similar lesions.
    • Laboratory tests

      M. hyopneuminiae - micro

      1. Histopathology of lung tissue infected with M. hyopneumoniae
      2. ELISA for detection of antibodies has limited use as antibodies may only be present 6 weeks after infection and test results need to be evaluated on a herd basis.
      3. PCR testing is done on lung tissue or lung flushes to demonstrate the M. hyopneumoniae antigen.
      4. Histological examination of lung tissue can reveal alveolar inflammation and peribronchiolar accumulations of lymphocytes.
      5. Sampling of colostrum for antibodies can support diagnosis in the early stages of the disease, but the sample must be collected within 2 hours after farrowing.

    To accurately diagnose M. Hyopneumoniae infection a combination of diagnostic tests is advised.

    mycoplasmae hyopneumoniae infection

    Macroscopic lung lesions in a pig infected with M. hyopneumoniae

    cross section M.hyopneumoniae infection

    Cross section of lung lobe - multiple pale foci within the affected lobules indicating bronchiolar orientation of the pneumonia.

    For more information about diagnosis and lung scoring in the slaughterhouse see:


    Treatment and Prevention of M. Hyopneumoniae infections

    • Prevention is very dependent on good management that provides an optimal environment for the pigs and thus decreasing pig susceptibility to M. hyopneumoniae. Attention to air quality, ventilation, temperature, stocking density, age segregation, and a strict all-in-all-out policy are very important in preventing the spread of this pathogen between pigs. In addition, segregated early weaning, multi-site production operations, and closing of the herd can further help to eliminate this pathogen.
    • Antibiotics are effective in the treatment and prevention of M. hyopneumoniae infections, timing is a real problem. Treating too late or too early is ineffective, so it often needs to be continued over an extended period. Medicated Early Weaning can produce litters free of M. hyopneumonia.


    Vaccination of piglets before the infection occurs can be an efficient strategy for preventing damage from M. hyopneumoniae infections.


procilis circumvent

Porcilis M Hyo