DISEASE CARRIERS 



491 



Cleanliness which destroys the breeding places of flies, the 

 frequent removal and destruction of garbage, rubbish, and manure, 

 the covering of all food when not in use, and especially the careful 

 screening of windows and doors during the breeding season are 

 wise precautions taken to prevent the spread of diseases by flies. 

 Far more important than to " swat the fly "is to remove their 

 breeding places ! 



Practical Exercise 21. What is the best method for destroying flies in your 

 home? Knowing when and where flies breed, when would be the best time 

 to " swat the fly "? How would this method compare with other ways of 

 extermination ? 



Other insect disease carriers. Fleas and bedbugs have been 

 added to those insects proved to carry disease to man. Bubonic 

 plague, which is primarily a disease of rats, is transmitted from 

 infected rats and ground squirrels to man by fleas. Fleas are also 

 believed to transmit from rats to rats a form of leprosy found only 

 in these animals. It 

 is thought probable 

 that bedbugs trans- 

 mit relapsing fevers. 

 Typhus fever is 

 transmitted by body 

 lice. 



Animals other than 

 insects that may 

 spread disease. The 

 common brown rat 

 is an example of a 

 mammal, harmful to 

 civilized man, which 

 has followed in his 

 footsteps all over the 



world. Starting from China, it spread to eastern Europe, thence to 

 western Europe, and in 1775 it had arrived in this country. In 

 seventy-five years it reached the Pacific coast and it is now fairly 

 common all over the United States, being one of the most prolific 

 of all mammals. Rats spread bubonic plague, the " Black Death " 



ground. 

 Scjuirrel 



Boccillusr 



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Explain from the diagram, how the bubonic plague is carried? 



