The House-fly as a Carrier of Disease 155 



Tuberculosis is one of the diseases which it is quite conceivable 

 may be carried occasionally. The sputum of tubercular patients 

 is very attractive to flies, and various workers, notably Graham- 

 Smith, have found that Musca domestica may distribute the bacillus 

 for several days after feeding on infected material. 



A type of purulent opthalmia which is very prevalent in Egypt 

 is often said to be carried by flies. Nuttall and Jepson (1909) 

 consider that the evidence regarding the spread of this disease by 

 flies is conclusive and that the possibility of gonorrhceal secretions 

 being likewise conveyed cannot be denied. 



Many studies have been published, showing a marked agreement 

 between the occurrence of typhoid and other intestinal diseases 

 and the prevalence of house-flies. The most clear-cut of these are 

 the studies of the Army Commission appointed to investigate the 

 cause of epidemics of enteric fever in the volunteer camps in the 

 Southern United States during the Spanish- American War. Though 

 their findings as presented by Vaughan (1909), have been quoted 

 very many times, they are so germane to our discussion that they 

 will bear repetition: 



"Flies swarmed over infected fecal matter in the pits and fed 

 upon the food prepared for the soldiers in the mess tents. In some 

 instances where lime had recently been sprinkled over the contents 

 of the pits, flies with their feet whitened with lime were seen walking 

 over the food." Under such conditions it is no wonder that "These 

 pests had inflicted greater loss upon American soldiers than the arms 

 of Spain." 



Similar conditions prevailed in South Africa during the Boer War. 

 Seamon believes that very much of the success of the Japanese in 

 their fight against Russia was due to the rigid precautions taken to 

 prevent the spread of disease by these insects and other means. 



Veeder has pointed out that the characteristics of a typical fly- 

 borne epidemic of typhoid are that it occurs in little neighborhood 

 epidemics, extending by short leaps from house to house, without 

 regard to water supply or anything else in common. It tends to 

 follow the direction of prevailing winds (cf . the conclusions of Hindle 

 and Merriman). It occurs during warm weather. Of course, when 

 the epidemic is once well under way, other factors enter into its spread. 



In general, flies may be said to be the chief agency in the spread of 

 typhoid in villages and camps. In cities with modern sewer systems 

 they are less important, though even under the best of such condi- 



