Sources of bovine tuberculosis in the United States

• Published in: Infection, genetics and evolution genetics and evolution, 2014-12, Vol.28, p.137-143
• Main Authors: Tsao, Kimberly, Robbe-Austerman, Suelee, Miller, Ryan S., Portacci, Katie, Grear, Daniel A., Webb, Colleen
• Format: Article
• Language: English
• Subjects: Animals; bovine tuberculosis; Cattle; Cervidae; Clonal complex; disease transmission; Evolution, Molecular; genetic relationships; geographical distribution; Host-Pathogen Interactions; imports; Mexico - epidemiology; Mycobacterium bovis; Mycobacterium bovis - classification; Mycobacterium bovis - physiology; Phylogeny; Phylogeography; Reservoir; Spillover; strain differences; Tuberculosis, Bovine - epidemiology; Tuberculosis, Bovine - microbiology; Tuberculosis, Bovine - transmission; United States - epidemiology; wild animals
• ISSN: 1567-1348; 1567-7257
• DOI: 10.1016/j.meegid.2014.09.025

•Analyzed Mycobacterium bovis population structure from national reports.•Cattle from US and Mexico carried closely related M. bovis strains.•Transmission from farmed cervids to US cattle supported.•Farmed cervids and wild cervids act as epidemiologically distinct host groups.•Multiple sources contributed to overall M. bovis maintenance in US cattle. Despite control and eradication efforts, bovine tuberculosis continues to be identified at low levels among cattle in the United States. We evaluated possible external sources of infection by characterizing the genetic relatedness of bovine tuberculosis from a national database of reported infections, comparing strains circulating among US cattle with those of imported cattle, and farmed and wild cervids. Farmed cervids maintained a genetically distinct Mycobacterium bovis strain, and cattle occasionally became infected with this strain. In contrast, wild cervids acted as an epidemiologically distinct group, instead hosting many of the same strains found in cattle, and the data did not show a clear transmission direction. Cattle from Mexico hosted a higher overall richness of strains than US cattle, and many of those strains were found in both US and Mexican cattle. However, these two populations appeared to be well-mixed with respect to their M. bovis lineages, and higher resolution data is necessary to infer the direction of recent transmission. Overall patterns of both host and geographic distributions were highly variable among strains, suggesting that different sources or transmission mechanisms are contributing to maintaining different strains.