Congenerics: What can be learned about pertussis from pertussis-like disease caused by other bordetella?

The evolution of Bordetella pertussis from B. bronchiseptica (or a B. bronchiseptica-like ancestor) occurred primarily through gene loss and genome rearrangement, mediated largely through the expansion in the copy number of insertion sequence element repeats in the B. pertussis genome. B. pertussis is attributed as the main causative agent of whooping cough. However, B. parapertussis and B. holmesii also cause disease that is very similar to that caused by B. pertussis (here termed pertussis-like disease). The evolution of B. parapertussis and B. holmesii displays striking similarities to that of B. pertussis and thus this chapter explores what might be gained from comparative studies of B. pertussis, B. parapertussis, and B. holmesii with regard to the understanding of whooping cough.