Dissemination and Evolution of Cholera on Local and Global Scales

Infectious diseases with complex life cycles or environmental reservoirs are extremely difficult to eradicate. Understanding their evolution (how new variants emerge) and ecology (where they originate and replicate) is therefore key to controlling them. Our goal is to change the way we approach infectious diseases, from a perspective of intervention to one of prevention. This is now possible using modern molecular microbial ecology approaches to monitor populations of human pathogens, both in their host and in the environment. My focus is on cholera, an ancient and often-fatal diarrheal disease with a complex ecology, which still affects 1.4 to 4.3 million people a year, causing between 28,000 to 142,000 deaths. Its causative agent is Vibrio cholerae, a bacterium with aquatic environmental reservoirs. New variants emerge constantly and have so far spread worldwide in three separate waves. We now know that cholera is constantly evolving in its endemic home, the Bay of Bengal, which is the ultimate source of all waves of the current pandemic. We believe that understanding the ecological and evolutionary dynamics of cholera in its natural home will not only save lives locally, but also prevent its spread abroad.

Our main goals

  1. Establish genomic epidemiology as a front-line approach
  2. Make molecular screening easy and cheap
  3. Understand asymptomatic carriage and its role in dissemination
  4. Determine inter-epidemic ecology in environmental reservoirs
Vibrio metoecus , the closest known relative of  Vibrio cholerae  (transmission electron micrograph in false colour by Paul Kirchberger)

Vibrio metoecus, the closest known relative of Vibrio cholerae (transmission electron micrograph in false colour by Paul Kirchberger)

Current projects

  • Cholera in Bangladesh: In collaboration with the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), we are surveying the Bay of Bengal to study the ecology of Vibrio cholerae, the coastal aquatic microbe responsible for the widespread diarrheal disease cholera, in a region where it is endemic.
  • Global Vibrio cholerae genome database: We are sampling Vibrio cholerae strains from around the world and sequencing their genomes to assemble a global reference database. This will allow the quick identification of the origin of new epidemics.
  • Origins of pandemic Vibrio choleraeWe are working on deciphering the geographical origin of the ancestor of strains responsible for causing the last seven cholera pandemics and reconstructing the history of its evolution step by step.
  • Emerging pathogen: We are following the emergence of a novel pathogen in North America, Vibrio metoecus, a close relative of the well-known Vibrio cholerae.
  • Antagonism as a natural population structuring tool: Using the Type VI Secretion System (T6SS) as a model, we explore how antagonistic interactions shape natural populations of Vibrio cholerae and how pathogenic strains may persist in environmental reservoirs.