title: Sources of bovine tuberculosis in the United States.
abstract: 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.
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, CO 80523, USA. Electronic address: kim.tsao@colostate.edu.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Tsao
authors.affiliation: USDA APHIS Veterinary Services, Science Technology and Analysis Services (STAS), National Veterinary Services Laboratories, Ames, IA, USA.
authors.forename: Suelee
authors.initials: S
authors.lastname: Robbe-Austerman
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, CO 80523, USA; USDA APHIS Veterinary Services, STAS, Center for Epidemiology and Animal Health, Fort Collins, CO, USA.
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Miller
authors.affiliation: USDA APHIS Veterinary Services, STAS, Center for Epidemiology and Animal Health, Fort Collins, CO, USA.
authors.forename: Katie
authors.initials: K
authors.lastname: Portacci
authors.affiliation: USDA APHIS Veterinary Services, STAS, Center for Epidemiology and Animal Health, Fort Collins, CO, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Grear
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Colleen
authors.initials: C
authors.lastname: Webb
mesh_terms: D000818:Animals; D002417:Cattle; D019143:Evolution, Molecular; D054884:Host-Pathogen Interactions; D008800:Mexico / Q000453:epidemiology; D009163:Mycobacterium bovis / Q000145:classification* / Q000502:physiology*; D010802:Phylogeny; D058974:Phylogeography; D014380:Tuberculosis, Bovine / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission*; D014481:United States / Q000453:epidemiology
keywords: Clonal complex; Mycobacterium bovis; Reservoir; Spillover