Rapid and sensitive detection of viable mycobacteria in bovine faeces and blood by a novel phagomagnetic separation (PhMS)-qPCR assay

Mycobacterium avium subsp. paratuberculosis (MAP) and Mycobacterium bovis are slow-growing mycobacterial pathogens that cause Johne’s disease (Paratuberculosis) and Bovine Tuberculosis, respectively. The potential of a new Phagomagnetic separation (PhMS)-qPCR assay to detect viable MAP and/or M. bovis in bovine faeces and blood within 24 h was investigated. Following careful optimization of sample preparation protocols, faeces samples (n=376) from calves and adult cattle on several Johne’s affected farms, and blood samples (n=174) from TB skin test reactor and routine slaughter <30 month old cattle collected at point of slaughter, were tested by PhMS-qPCR and culture. Results of faecal testing demonstrate that the novel PhMS-qPCR assay can quickly detect calves or cattle shedding viable MAP, i.e. infectious animals. Results of blood testing revealed that viable MAP and/or M. bovis mycobacteraemias were readily detectable in cattle at slaughter in Northern Ireland, with co-infections (both MAP and M. bovis detected in same blood sample) frequently encountered. Collectively, results indicate that the novel PhMS-qPCR assays may represent new diagnostic tests for Johne’s disease and bovine Tuberculosis in the future.