THE RAT IN RELATION TO INTERNATIONAL SANITATION. 



By Asst. Surg.-Gen., JOHN W. KERR, 

 Public Health and Marine-Hospital Service. 



Rats, like man, had their origin in Asia, from which continent 

 they have finally become disseminated throughout the world. They, 

 too, like man, are great travelers, and therefore prey on the com- 

 merce of the ships in which they are carried. For this reason, and 

 on account of the fact that they are subject to plague and may 

 transmit the disease from one country to another, these animals have 

 an influence on international policy, and their control aboard ships 

 is an international problem. 



It has been estimated that there are as many rats as there are 

 human beings, and that each rat causes each day a loss by the de- 

 struction of material of at least half a cent. 



Assuming that the rat population aboard ships is as great as the 

 human population and my experience gained during the fumigation 

 of ships to kill rats convinces me that on the whole it is greater 

 some idea may be had of the enormous migrations of rats and the 

 toll they exact for food from international commerce. Some idea 

 can also be had of the danger of rats in transmitting plague when 

 it is remembered that 51 countries have been infected with the 

 disease since the present pandemic began in Canton, China, in 1894, 

 and when it is known that at least 146 ships have had plague infection 

 on board during that time. 



During the International Sanitary Conference of Paris in 1903 

 the influence of the rat in transmitting plague was borne in mind, 

 and the international sanitary agreement, which was signed ad 

 referendum December 3, 1903, requires the destruction of rats aboard 

 plague-infected ships, recommends it on ships suspected of being 

 plague infected, and permits it on ships indemne from plague. The 

 ship is considered indemne from plague which, although coming 

 from an infected port, has had neither death nor case on board 

 either before departure, during the voyage, or at the moment of 

 arrival. 



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