BSC 201 Lecture Notes - Lecture 9: Smallpox, Group Selection, Peaceful Coexistence
Document Summary
Evolutionary ecology of virulence: pathogen/parasite populations are evolving entities, natural selection determines parasite traits, parasite trait values will depend greatly on ecology. What is virulence: harm done to a host by an infecting parasite. Decrease in fecundity: caused by parasite exploiting host to reproduce, capacity of a parasite to inflict damage and reduce host fitness, parasite property, but measured in host. What do we mean by virulence: infection attaches to host, parasite multiplies and grows. Survival/reproduction (host fitness: and then transmission, avirulence: lacking virulence to virulence is the spectrum. Variation of virulence: rhinovirus mild, dengue more severe, west nile strain variation. Relevant in some situations: traditional adaptive view (avirulence theory) Misses important facets: adaptive virulence and the trade-off hypothesis. Non-adaptive virulence: coincidental virulence in dead-end hosts, accidental infections, with no/limited further transmission, virulence is due to traits evolved in natural host, ex: echinococcus (fox tapeworm), rabies, ebola. Evolutionary fitness of parasites: depends on the spread: transmission, basic reproductive number.
