Diagnosis of M. hyo infection

Diagnosis is based on

  • Clinical signs – chronic, non-productive coughing
  • Lung lesions upon necropsy
    • Lungs are meat-like and purple-gray in color.
    • 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
    • Histopathology of lung tissue infected with Mycoplasma hyopneumoniae (M. hyo)
    • Enzyme-linked Immunosorbent Assay (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
    • Polymerase Chain Reaction (PCR) testing is done on lung tissue or lung flushes to demonstrate the M. hyo antigen
    • Histological examination of lung tissue can reveal alveolar inflammation and peribronchiolar accumulations of lymphocytes
    • 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. hyo infection, a combination of diagnostic tests is advised.

Macroscopic lung lesions in a pig infected with M. hyo
Cross section of lung lobe – multiple pale foci within the affected lobules indicating bronchiolar orientation of the pneumonia
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