Risk factors associated with Johne's disease in a captive wood bison herd

Mycobacterium avium subsp. paratuberculosis (Map) has been identified in a wide range of domestic and wild ruminants. Captive wildlife, including Bison spp., can experience Johne's disease-related epidemiological scenarios similar to those seen in cattle. To date, there is no epidemiological information about Map in captive wood bison (Bison bison athabascae) herds. The objective of this study was to examine age, sex, and location-specific density as potential risk factors associated with Map positivity in a captive wood bison herd located in Alberta.

Fecal samplings were obtained from October 2021 to October 2022, DNA was extracted, and qPCR targeting IS900 and F57 followed by liquid culture confirmation was completed. Within-herd prevalence of IS900/F57 qPCR in October 2021 was 4.7%; prevalence of IS900 qPCR with culture confirmation was 6.8%. Regression analysis using 3 different outcomes based on different diagnostic approaches was employed: "base scenario" (positive result by fecal IS900 qPCR with culture confirmation of IS900/F57 qPCR), "scenario 1" (positive result by fecal IS900 qPCR with culture confirmation of IS900 qPCR), and "scenario 2" (positive result by fecal F57 qPCR with culture confirmation of F57 qPCR). Wood bison in the age group ≥ 6 to 9 y were more likely to be Map-positive in all scenarios. Location B (higher animal density) was significantly associated with animals being Map-positive in base scenario and scenario 1.

This study identified risk factors related to Johne's disease in a captive wood bison herd. The findings can be used to initiate more studies in both the commercial and wild wood bison herds.