Mycobacterium avium subsp. paratuberculosis in a captive wood bison herd: diagnostics and disease dynamics overtime
Date
2024-01-23
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Abstract
Mycobacterium avium subsp. paratuberculosis (Map) has been identified in a wide range of domestic and wild ruminants. Captive wildlife can experience JD-related epidemiological scenarios similar to those in cattle. In wood bison (Bison bison athabascae), an iconic and keystone species in Canada, Map DNA has been reported in fecal samples from clinically healthy animals. However, there is apparently no published information regarding clinical presentation of JD and its significance in wood bison. The objective of this study was to determine to what extent Map can affects a captive bison herd located in northeastern Alberta, Canada. The first part of the study was the detection and isolation of Map in clinical cases. Necropsies were performed on six wood bison and 24 samples were collected from each bison. The highest frequency of positive samples was observed with tissue culture 62.5% (90/144) followed by F57/IS900 qPCR 43.1% (56/130), and histopathology 29% (38/131). Distal jejunum and its associated lymph nodes were the most reliable tissue samples for detecting Map, irrespective of tissue autolysis or absence of visible lesions. Strain typing revealed a type II (cattle) strain, second clade. The second part of the study focused on Map status in the herd by obtaining within-herd prevalence, evaluating the impact of a test and cull strategy and potential risk factors associated with Map. At the outset, within-herd prevalence was 4.7% based on IS900/F57 qPCR and 6.8% with IS900 qPCR with culture confirmation. The following year, after we calculated a 56.3% of culling rate of positive animals, the within herd prevalence observed by IS900/F57 qPCR was 4.2% and 9.9% by IS900 qPCR with culture confirmation. Bison in the age group ≥ 6-9 years were more likely to be Map positive. Furthermore, the location with the higher number of animals was significantly associated with being Map positive. Information from this study can contribute to control strategies in the bison herd studied, by obtaining the appropriate tissue samples selection at the necropsy and by targeting the age group most likely to be Map positive. Additionally, based on the prevalence obtained in this study, sampling size calculations can be performed to carry out studies at a herd level. However, it is important to understand that the best strategy to reduce the prevalence of JD depends on specific objectives and characteristics of each bison herd.
Description
Keywords
Paratuberculosis, Wood bison, Johne's disease
Citation
Hernandez Reyes, A. L. (2024). Mycobacterium avium subsp. paratuberculosis in a captive wood bison herd: diagnostics and disease dynamics overtime (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.