THE HOUSE FLY AND DISEASE 79 



Tuberculosis. — It has been known for many years that flies 

 carry the bacillus of tuberculosis (Fig. 48, B), and everything 

 seems to point to the conclusion that the disease is at least to 

 some extent spread by them. Flies are attracted by sputum, 

 and when they chance to alight on that of tuberculous persons, 

 they take the bacilli into their intestines. Here the germs may 

 remain for days, during which the flies distribute them in their 

 excreta. The chief danger is from carelessness in the disposal 

 of sputum from tuberculous patients, since flies may easily carry 

 the germs to food. Some idea of the losses from tuberculosis 

 in this country may be judged from the following statistics. 1 



In 1906, 138,000 persons died from tuberculosis in the United 

 States, or at the rate of 164 per 100,000 population. Based 

 upon these facts, it is estimated that about 5,000,000 of those 

 now living in the United States will die of the disease. It is 

 claimed that the disease alone costs the United States from 

 $400,000,000 to $1,000,000,000 each year (Fisher). 



It is estimated by the United States Bureau of Animal Indus- 

 try that 2 per cent of hogs in the United States are tubercular, 

 and that losses of stock in the United States, due to tuberculosis, 

 amount to $23,000,000 annually. Of 400,000 cattle tested in 

 the United States 9.25 per cent were tubercular. 



Asiatic Cholera. — Asiatic cholera is a disease common in 

 India, from which place it frequently spreads throughout the 

 world. Several epidemics have occurred in America, and New 

 Orleans and other seaports are often threatened. The germ 

 that causes cholera is a spirillum bent in the form of a comma 

 (Fig. 48, C.) It gains entrance to the human body in food or 

 drink and lodges in the intestines. The method of spreading 

 cholera germs is therefore very similar to that of the typhoid 

 bacilli. The house fly is an important carrier and preventive 

 measures should be taken accordingly. 



Other Diseases. — Not so much is known about the other 

 diseases that may be caused by germs distributed by flies. Cer- 



1 Marshall, C. E., Microbiology. 



