752 



THE MONTHLY BULLETIN. 



that they readily became victims of disease. Whether the disease 

 observed among squirrels as early as 1902 can be associated with the 

 infection actually verified in 1908 at the laboratories of the United 

 States Public Health Service as bubonic plague, can not be determined 

 definitely owing to lack of tests. It was suspected, however, by officers 

 of the health service that such a condition existed as early as 1903?. 



Bubonic plague, as a disease, was first observed in San Francisco in 

 1900, and in February, 1901, six out of thirteen suspected human plague 

 cases in Chinatown proved, upon special investigation, to have been 

 that disease. Deaths to the number of 113 brought a cessation of human 

 cases in about four years, but after the earthquake, in 1907, new cases 

 began to appear. Thorough measures were inaugurated to suppress the 

 increase of rats, which were the then known disseminators of the 

 infection, and rigid enforcement of sanitary ordinances was followed. 

 Bounties were even paid on rats, entailing the outlay of a considerable 

 sum annually. Proofing against this rodent, use of poisons and 

 trapping, was continued as before. 



In the fall of 1908, cases of bubonic plague among ground squirrels 

 were isolated from Contra Costa and one ease from Los Angeles. This 

 last-mentioned case was not followed by others, as happened with others 

 in the state. As much information as could be obtained on the life his- 

 tory and habits of rodents was disseminated in the infested areas to keep 

 residents on guard for cases of plague. During the following year 

 plague continued to be found among squirrels, chiefly in Contra Costa 

 County, and a state-wide hunting campaign to learn the extent of 

 plague infection was carried on; at the same time every effort was 

 being made to destroy squirrels locally in Contra Costa. 



A law was approved in March of 1909 1 so modeled as to make the 

 extermination of rodent pests a duty of all landowners. Unfortunately 

 this law was thought unconstitutional, and it was judged advisable to 

 await action of a later legislature before the legal phase should be 

 again put in suitable shape. 



CAMPAIGN OP U. S. PUBLIC HEALTH SERVICE. 



After an intensive search over a large portion of the state, many 

 counties were found to harbor plague-infected squirrels in regions where 

 the safety to human health was seriously jeopardized. Consequently, 

 during the fall of 1909, a general campaign of eradication was to be 

 conducted, especially in Contra Costa County. Free poisoned grain 

 was distributed, as well as carbon disulphid, to the residents of the 

 above county, with the agreement that it be judiciously and economically 

 used. Results of a successful nature were reported, and as a safeguard 

 against a possible influx of plague infection the idea of a " squirrel-free 

 zone" was carried out by actual operations, which zone reached its 

 highest point of efficient protection in 1913. Toward the end of 1911 

 the hunting had been .extended to 45 counties of the state, but cases of 

 plague among squirrels were discovered in only 12. Infected squirrels 

 killed east of the San Joaquin River began to cause anxiety in that 

 the ground squirrels were ranging to the mountain passes, the altitudes 

 of which were lower than were the highest elevations at which the 



statutes and Amendments to the Codes, California, 1909, extra sessions 1907, 

 chap. 204, p. 311. 



160 



