Roadmap for development of disease control strategies for bTB

What are we trying to achieve and why? What is the problem we are trying to solve?

To understand the evolution and epidemiology of M. bovis, surveillance, methods, and data have essentially two
applications:

1. To investigate important aspects of bovine TB epidemiology – transmission dynamics, phenotypes using descriptive, analytical and disease modelling studies
2. To inform outbreak investigations, case studies and contact tracings (test, track-and-trace – risk pathway assessment)

What are the scientific and technological challenges (knowledge gaps needing to be addressed)?

• Due to test and lab confirmation sensitivity issues, not all TB cases yield an isolate for molecular typing.
• Challenge to undertake structured surveillance over time, at herd- or animal-level.
• Transmission dynamics (phylodynamic) modelling is challenging with such a slowly evolving pathogen.
• Wildlife likely to be significantly under sampled compared to cattle.
• Currently expensive – SNP-based testing might provide a “triage” and sequencing directly from tissue samples would be desirable.

What approaches could/should be taken to address the research question?

• Whole-genome sequencing provides significantly improved information content, functionality, and resolution.
• Much has been learned about TB epidemiology from previous molecular epidemiology tests and studies; need to understand the extent of correlation between tests.

What else needs to be done before we can solve this need?

Most reference labs are proficient in these techniques.

Existing knowledge including successes and failures

• Molecular typing provides “Information for action” – tools to help understand bovine TB spread and persistence, to rule TB herds and/or animals in or out of clusters, and evidence to help identify where transmission can be interrupted.
• Due to low rates of molecular evolution, outbreak settings can be very genetically homogeneous. So source tracing with molecular data needs to be supported by animal and herd level data on movements, test histories etc.