Abstract
Control of bovine tuberculosis (bTB), caused by Mycobacterium bovis , in the Republic of Ireland costs €84 million each year. Badgers are recognized as being a wildlife source for M. bovis infection of cattle. Deer are thought to act as spillover hosts for infection; however, population density is recognized as an important driver in shifting their epidemiological role, and deer populations across the country have been increasing in density and range. County Wicklow represents one specific area in the Republic of Ireland with a high density of deer that has had consistently high bTB prevalence for over a decade, despite control operations in both cattle and badgers. Our research used whole-genome sequencing of M. bovis sourced from infected cattle, deer and badgers in County Wicklow to evaluate whether the epidemiological role of deer could have shifted from spillover host to source. Our analyses reveal that cattle and deer share highly similar M. bovis strains, suggesting that transmission between these species is occurring in the area. In addition, the high level of diversity observed in the sampled deer population suggests deer may be acting as a source of infection for local cattle populations. These findings have important implications for the control and ultimate eradication of bTB in Ireland.
Highlights
Bovine tuberculosis, caused by Mycobacterium bovis, affects cattle populations around the world [1,2,3,4]
All the M. bovis genomes sourced from infected cattle, badgers and deer in the Wicklow area were within 35 single nucleotide variants (SNVs) of one another (Fig. 4)
There were multiple instances of M. bovis genomes sourced from cattle and wildlife being less than three SNVs apart, a distance that, in the human field, is indicative of recent transmission of Mycobacterium tuberculosis [51]
Summary
Bovine tuberculosis (bTB), caused by Mycobacterium bovis, affects cattle populations around the world [1,2,3,4]. In many countries with endemic bTB, wildlife play a role in the spread and persistence of M. bovis infection in cattle, complicating bTB control [3, 5,6,7,8]. Populations of the European badger (Meles meles) can maintain M. bovis and act as a source of infection for cattle [10, 11]. Badger populations across the country are managed as part of the national bTB control programme [12]. While deer are susceptible to infection, their role in M. bovis spread and persistence is uncertain due to
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