Both isolation and PCR tests are available but both suffer from a lack of sensitivity. Samples for isolation can be obtained from the oropharynx (swabs) or through transtracheal wash/ broncheo-alveolar lavage. Cytological analysis of tracheal washes show polymorphonuclear leucocytes, macrophages and bacteria [Welsh 1996].
For isolation, swabs should be placed into charcoal Amies transport medium, although ordinary Amies transport medium can also be used. Bb should be cultured on an appropriate selective medium such as charcoal/cephalexin agar, which reduces overgrowth by other respiratory flora. The identification of Bb form bronchoalveolar lavage samples from cats with lower respiratory signs can be considered to be diagnostic. Interpretation of the significance of the identification of Bordetella in oropharyngeal swabs from cats with predominantly URT signs is less clearcut but will usually be considered as an indication for appropriate antibiotic treatment. Positive culture from oropharyngeal swabs from cats from multicat households have to be interpreted with the awareness that the prevalence of infection is higher in cats from crowded environments and that the bacterium may simply be present co-incidentally and other causes of presenting clinical signs must be considered.
Sensitive real-time PCR assays have been described that are capable of discriminating between different bordetella and detecting less than 10 genome copies of Bb per µl [Koidl et al., 2007]. Some laboratories have developed multiplex assays that allow the detection of all common feline respiratory pathogens in one assay. Unfortunately, such assays often have a negative impact on the sensitivity of such assays [Helps et al 2005].
Serological diagnosis is of limited diagnostic use due to the high seroprevalence in the general cat population.