YELLOW FEVER 487 



lives near water, seldom going more than 150 feet from the banks 

 of streams or lakes. The British government has attempted to 

 control the disease in Uganda by moving all the villages at least 

 two miles from the lakes and rivers. Among other diseases that 

 may be due to protozoans is kala azar, a fever in hot Asiatic 

 countries which is probably carried by the bedbug, and African 

 tick fever, carried by a small insect called the tick. In this 

 country many fatal diseases of cattle, as " tick fever," or Texas 

 cattle fever, are caused by protozoa. 



Self-Testing Exercise 



Malaria is caused by a (1) which is carried by the 



(2) (3). It lives part of its life in the body of the (4) 



and part in . . •. (5). When the (6) bites a person, it 



passes the (7) into the (8) with its saliva. Malaria 



can be eradicated by (9) the (10) (11) of 



(12). Other diseases probably caused by protozoans are 



(13), (14) (15), (16), and 



(17) (18). 



PROBLEM VIIL HOW WAS THE CAUSE AND CONTROL OF 

 YELLOW FEVER DISCOVERED? 



Yellow fever and mosquitoes. Another disease carried by 

 mosquitoes is yellow fever. In the year 1878 there were 125,000 

 cases and 12,000 deaths in the United States, mostly in Alabama, 

 Louisiana, and Mississippi. During the French attempt to con- 

 struct the Panama Canal, the work was at a standstill part of the 

 time because of the ravages of yellow fever. Before the war with 

 Spain, thousands of people were ill in Cuba. But today yellow 

 fever has almost disappeared, both there and in the Canal Zone, 

 through proper control of the fever-carrying mosquito Aedes. 



The knowledge that Aedes carries the disease-producing agent 

 that causes yellow fever is due to the experiments in 1900 of a 

 commission of United States army officers, headed by Dr. Walter 

 Reed. One of these men, Dr. Jesse Lazear, lost his life in an ex- 

 periment to prove that yellow fever is transmitted by mosquitoes. 



