Correlation between bacterial culture and IS 900 qPCR to detect Mycobacterium avium subsp. paratuberculosis in the feces of sika deer

Mycobacterium avium subsp. paratuberculosis (MAP) infection in deer causes paratuberculosis (PTb; Johne disease), a slowly progressive chronic granulomatous enteritis. Accurate and rapid detection of MAP shedding by subclinical animals is essential for effective control of infection in deer herds. The VetMAX MAP 2.0 qPCR assay targeting IS 900 was developed for cattle, sheep, and goats. However, the performance of the assay in sika deer ( Cervus nippon ) has not been evaluated. Here, we describe the use of the VetMAX MAP 2.0 qPCR assay on fecal samples from sika deer for the detection of MAP and its correlation with bacterial culture. DNA was extracted from fecal samples from 115 sika deer with known culture results (79 from a PTb-endemic herd and 36 from a PTb-free herd), using the QIAamp PowerFecal Pro DNA extraction kit. Diagnostic sensitivity and specificity were 100% (76 of 76) and 92.3% (36 of 39), respectively, with an overall accuracy of 97.4% compared with bacterial culture. A strong positive correlation was observed between culture time to detection and the qPCR Cq-value ( r = 0.70, area under the curve = 0.96). Our findings offer correlation between bacterial culture and VetMAX MAP 2.0 qPCR assay results in feces of farmed sika deer and highlight the quantitative value of the qPCR assay as a rapid indicator of bacterial load and shedding intensity.