In 1911, McCoy and Chapin,1 while investigating a fatal epidemic of what was supposed to be bubonic plague in the California ground squirrels, isolated a small, gram-negative, nonmotile and nonsporebearing pleomorphic organism, which they named Bacterium tularense, since it was found in Tulare County, California.
During their investigations two of the laboratory workers contracted what was later found to be the human form of this infectious disease. These are the first proved cases of tularemia in man to be recorded.
Tularemia is only secondarily a human disease, being primarily a fatal bacteremia of wild rodents. In nature it has thus far been found in the ground squirrel, wild rabbits and hares, wild rats and wild mice. It is transmitted to man by the bite of an intermediate host, by the bite of contaminated animals or by self-inoculation. The intermediate hosts include horse-flies, wood-ticks, bedbugs and fleas. In most