Pathology and Bacteriology of Plague in Squirrels

THIS report is based upon 70 plague-infected ground squirrels (Citellus beecheyi) which have come under observation in California during the months of June, July, and August, 90o9. During this period approximately 200 squirrels have been reported as plague infected to Surgeon Rupert Blue, Public Health and Marine Hospital Service, commanding the plague suppressive measures. In the case of the majority of these, the diagnosis was based upon the gross lesions alone or upon the gross lesions in addition to the result of the microscopical examination of the smear preparations from the buboes or from other tissues. In the case of 68 of the squirrels, however, tissues were inoculated into laboratory animals and when these animals died, cultures were made from their tissues and the specific bacillus isolated in about 30 cases. In the other cases the postmortem lesions presented by the laboratory animals were so characteristic of plague that it did not seem necessary to make cultures from them. In a few cases the cultures were hopelessly contaminated and the effort to isolate the plague bacillus was abandoned. In two cases the bacillus was isolated directly from the tissues of a naturally infected ground squirrel. Indeed the attempt to recover the plague bacillus in this manner has been made on only about a half-dozen occasions. The reason that the effort was not made to