Evaluation of loop-mediated isothermal amplification (LAMP) assay for detection of aprV2 positive Dichelobacter nodosus in-field by secondary users

OBJECTIVE: Dichelobacter nodosus is the primary aetiological agent of footrot in sheep. Ovine footrot causes considerable economic losses and substantial animal welfare issues in the Australian sheep industry. Current methods for detecting D. nodosus are difficult, laborious and time-consuming. Recently, we developed a robust LAMP assay (VDN LAMP) that was able to identify aprV2 positive D. nodosus in-field. A major advantage of LAMP technology is the ability of the assay to be performed by non-specialists with minimal training. We aimed to assess the performance of the VDN LAMP in-field in comparison to a laboratory-based aprV2/aprB2 rtPCR when used by secondary users after training by the authors. RESULTS: Two animal health officers (termed secondary users) from Department of Primary Industries and Regions, South Australia (PIRSA) were trained in the use of VDN LAMP, before carrying out in-field testing on several locations in South Australia. The performance of VDN LAMP assay by secondary user 1 was shown to successfully detect 73.91% (n = 53) aprV2 positive samples, while secondary user 2 detected 37.93% (n = 30) aprV2 positive samples. Overall, the ability to identify virulent D. nodosus by VDN LAMP by secondary users was mixed for various reasons, however, this could be rectified by additional training and commercial production of the LAMP kits to increase stability. We envisaged in the future VDN LAMP will able to be used by non-specialists to aid control programs.