Detection of Mycoplasmopsis (Mycoplasma) bovis in formalin-fixed, paraffin-embedded bovine lung sections by immunohistochemistry and in situ hybridization.

The bovine respiratory disease complex (BRDC) is a multifactorial disease of economic importance in cattle involving viral and bacterial agents and several environmental and host-associated predisposing factors. Mycoplasmopsis (Mycoplasma) bovis is frequently detected in BRDC cases, but the role of this bacterium in the pathogenesis of BRDC is not completely understood. We explored the utility of routine histopathology and compared immunohistochemistry (IHC) and in situ hybridization (ISH) in pneumonic bovine lung tissue samples for the detection of M. bovis infection. Samples were analyzed for M. bovis using mycoplasma bacterial culture (screening test), H&E staining, IHC, and ISH. We found that "compatible histologic lesions" are not entirely predictive of the presence of M. bovis on culture, IHC, or ISH, and also that there was no statistical difference between IHC and ISH for detecting M. bovis. We conclude that IHC and ISH can be used interchangeably to detect M. bovis infections in pneumonic bovine lung.