Diagnosis of Bovine Respiratory Disease Complex (BRDC)

A definitive diagnosis of the pathogens involved in respiratory disease in cattle requires laboratory testing.

Diagnostics in respiratory disease is based on a combination of:

• clinical examination
• laboratory testing
• post mortem examination

Clinical examination

Recording of respiratory rate and type, rectal temperature and observation for clinical signs. Additionally, non-invasive methods like chest radiography and ultrasonography or lung function testing with the forced oscillation technique may be used for a more detailed diagnosis. Clinical signs and gross pathology in respiratory disease are rarely pathognomonic, which makes it difficult to identify the causative agent(s) exclusively based on the clinical examination. Moreover, mixed infections are the rule rather than the exception. Therefore, laboratory testing is often required for a proper diagnosis.

Laboratory testing

Most veterinary diagnostic laboratories offer methods for antibody testing for the common respiratory pathogens. Antibody testing should be done on paired blood samples, because detection of antibodies in a single sample has little diagnostic value. Isolation of viruses or bacteria or detection of specific nucleic acids in nasal or naso-pharyngeal swab samples is technically very demanding. While detection of the viruses BRSV, PI3 or BoHV‑1 in the upper respiratory tract justify the statement, that they are the cause of the disease, M. haemolytica are a common bacterial inhabitant in the upper respiratory tract of healthy cattle. Therefore, broncho-alveolar lavage fluids or lung tissue are more suitable samples for isolation of detection of M. haemolytica and P. multocida.

Pneumonia seen in a lung lobe at post mortal examination.