The Ten Plagues from the Point of Evolutionary Biology of Infectious Diseases
The story of Ten Plagues in Egypt provides meaningful and functional principles for comprehending evolution and manifestation of epidemics of zoonotic infections such as plague. Etiological agent of plague is a bacterium Yersinia pestis existing under specific ecological conditions within endemic areas. Previously scientists believed that Y. pestis co-evolved with its mammalian hosts for millennia. Recent bacterial genome analyses demonstrated that a relative Y. pseudotuberculosis clone acquired properties of plague pathogen only few thousands year ago. Likely, it happened in Middle East or in Central Asia. Plague, as a disease, is not just a collection of individual cases due to appearance of a particular etiological agent. There are complex processes that precede massive epidemics. Modern research of evolution of zoonotic diseases may consider specific parameters driving epidemics, but the Ten Plagues’ narrative provides an unprecedented picture of plague evolution in its complexity. Each plague described in Exodus represents a specific stage (phase), which is necessary and sufficient for plague evolution. The ten stages include (1) dramatic environmental disruption – ‘Dam’; (2) sudden change of ecological niche for a principal animal species – ‘Tsefaredeim’; (3) presence of insect vectors for infection transmission – ‘Kennim’; (4) critical level of diversity (mixture) of wild animals – ‘Arov’; (5) epizooty among wild and/or domestic animals – ‘Dever’; (6) microbial evolution leading to specific pathogenesis – ‘Shkhin’; (7) rapid climate change – ‘Barad’; (8) invasion of alien biological species – ‘Arbeh’; (9) social disturbance – ‘Hoshekh’; and finally (10) epidemics manifested with a high incidence of fatal cases – ‘Makat Bechorot’.