Real-time PCR demonstrates a higher prevalence of Mycoplasma bovis in Northern Ireland compared with sandwich ELISA

Mycoplasma bovis has come to be recognised as a major contribution to calf pneumonia worldwide, with very few countries being free of its impact (Nicholas 2012). Its contribution to the disease is complex, and yet to be fully determined (Caswell and Archambault 2008). Since its arrival in Northern Ireland in 1993, it has featured in up to 25 per cent per annum of all cases submitted to the Veterinary Sciences Division for diagnostic investigation (Brice and others 2000, Blackburn and others 2007). The routine diagnostic detection of M bovis at this laboratory, has been done using a capture/enrichment sandwich ELISA (sELISA) on pneumonic lung samples (Ball and others 1994b). This assay utilises a culture stage to confirm sELISA-positive results, and only confirmed results are reported as positive. The failure to detect/confirm M bovis in samples may be due to the presence of therapeutic antimicrobials and other bacteria present in the tissue. Antimicrobials can inhibit mycoplasma growth during the enrichment stage of the assay preventing the organism reaching detectable levels for the sELISA, and other bacteria can overcome the selectivity of the mycoplasma media, and mask positive results when present in high numbers (Blackburn and others 2008). Real-time PCR (qPCR) assays have been developed in recent years for the detection of M bovis in milk samples and from nasal and conjunctival swabs (Cai and others 2005, Clothier and others 2010, Sachse and others 2010). This diagnostic approach is not directly affected by the presence of antimicrobial agents and other bacteria, and in this study, was applied to the detection of M …