Date of this Version At the first Vertebrate Pest Control
Conference in 1964, I traced the history of plague control in
California and outlined a revised approach, based on newer
concepts of plague ecology. In our state of relative ignorance,
this required a number of unproved assumptions about plague
occurrence in California that verged on crystal ball gazing.
These were principally that (1) plague persists in relatively
resistant rodent species in certain favorable locations, (2)
ground squirrels and chipmunks experience periodic epizootics,
but are not permanent reservoirs, (3) plague "foci" of the past
were merely sites of conspicuous epizootics, they did not
necessarily correspond to permanent foci, and could result from
epizootic migrations over considerable distances, and (4) a
number of assumptions about areas of greatest epizootic
potential can be made by analyzing the pattern of recurrent
plague outbreaks in the past. Since then the validity of these
assumptions has been tested by the largest outbre