The presence of the disease can be detected in two ways: detection of the causal organism in affected tissue, and detection of serum antibodies to the organism.
The causal organism, MmmSC, can be demonstrated in the fluid present in the chest and in diseased lung by culture, by antigen detection tests (interface precipitin test or agar gel immunodiffusion test) and by a polymerase chain reaction (PCR) test.
The rapid slide agglutination test using whole blood or serum for antibody detection can be a useful test to detect infected herds; it can be used in the field to give rapid results. It is performed by mixing a drop of a suspension of killed and stained MmmSC organisms with a drop of serum or blood on a glass slide. In a positive result, aggregates form within one minute.
At present, the laboratory test of choice for detecting serum antibodies is the complement fixation test (CFT). Great care is needed in collecting and storing sera to be used for this test. The competitive ELISA test is equally sensitive and useful as a herd test. Histopathology of affected lung fixed in 10% formalin can also help in confirming the diagnosis. The peroxidase-antiperoxidase (PAP) test is an excellent test.
Samples required for successful confirmation of CBPP are chest fluid, diseased lung, and regional lymph nodes, kept on ice during transportation to the laboratory. Additional samples may be fixed in 10% formalin solution for histopathology.
Serum used for antibody tests is obtained by allowing blood to clot at room temperature and collecting the clear liquid when the clot contracts. This usually takes a few hours and during this time the blood samples should be kept at ambient temperature. Separated sera should be kept on ice, and transported quickly to the laboratory.
Culture and antigen detection tests provide conclusive confirmation of CBPP diagnosis.
It is important to note that Pasteurella spp. bacteria can frequently be cultured from any pneumonic lung (and even from normal lung). Thus, their isolation does not indicate a diagnosis of pasteurellosis nor does it rule out the diagnosis of CBPP.
The slide agglutination test can give false-positive results in uninfected animals, and also antibodies become undetectable by this test as the disease progresses. Therefore it can not be used reliably for individual animals.. It is useful in detecting infected herds early in the course of the disease. The CFT is the most reliable test currently available, but it should be noted that false-negative results could be found early and late in the course of the disease.
