PLAGUE ERADICATION IN CITIES BY SECTIONAL 

 EXTERMINATION OF RATS AND GENERAL RAT 

 PROOFING. 



By Victor G. Heiser, 

 Passed assistant surgeon, U. S. Public Health and Marine-Hospital Service, chief quaran- 

 tine officer and director of health for the Philippine Islands. 



The health officials of the city of Manila, P. I., for the five-year 

 period from 1900 to 1905 made most valiant efforts to destroy the rats 

 of the city; approximately $15,000 were paid in rat bounties and 

 $325,000 in salaries and wages and other expenses for rat catching, 

 but at the end of that time the rats were apparently as plentiful as 

 before and the plague was still present. The experience in Tokio 

 and Osaka had been practically the same. Professor Kitasato 

 expressed the opinion that a given city could only have up to a certain 

 number anyhow, because further increase was limited by the amount 

 of available food, and when the limit had been reached the rats 

 commenced to eat one another, which prevented more than a certain 

 number ever being present, and that the increase by breeding was 

 about as rapid as any method of destruction which had yet been tried. 



The following plan was then tried, and the plague among human 

 beings soon disappeared, there being no cases since April, 1906; and 

 it has been eradicated among rats each time that it has made its 

 appearance. 



A list of the places at which plague-infected rats were found was 

 made. Each was regarded as a center of infection. Radiating lines, 

 usually five in number, were prolonged from this center, evenly spaced 

 like the spokes of a wheel. Rats were caught along these fines and 

 examined. Plague rats were seldom found more than a few blocks 

 away. The furthermost points at which infected rats were found 

 were then connected with a line, as is roughly shown in the diagram 

 on page 206 (Fig. 59.) 



The space inclosed by the dotted line was regarded as the section of 

 infection. The entire rat-catching force, which had heretofore been 

 employed throughout the city, was then concentrated along the border 

 of the infected section; that is, along the dotted line. They then 

 commenced to move toward the center, catching the rats as 



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