FLIES AND OTHER HOUSEHOLD INSECTS 11 



that during the fly season great attention should be paid to the 

 screening of rooms and hospital wards containing patients with 

 tuberculosis and laboratories where tubercular material is examined.' 



The evidence showing that flies may play an important part in 

 the diffusion of cholera is, according to Dr Nuttall, absolutely con- 

 vincing. He cites experiments showing that cholera bacilli may 

 be found on flies in large numbers, while they may occur in the 

 dejecta within 17 hours after feeding and as late as four days. 

 Infected flies have been given access to milk and cholera cultures 

 made therefrom. 



Dr Nuttall considers that the evidence previously submitted 

 proves that the house fly may carry about and deposit anthrax 

 bacilli, though there may be a question as tO' how generally flies are 

 responsible for the dissemination of this disease. Parke admits the 

 possibilities of flies distributing, in addition to diseases mentioned 

 above, plague, trachoma, septicemia, erysipelas and leprosy. Fur- 

 thermore, there are those who would hold flies responsible for the 

 more frequent new cases which occur in the zone immediately sur- 

 rounding the smallpox hospital and which may be due either to 

 the wafting out of infected particles or their carriage by flies. 

 The latter is considered the more probable. Yaws or framboesia 

 is a tropical infection carried by this household pest. Howe, ac- 

 cording to the statement of Dr Howard, has demonstrated that the 

 purulent conjunctivitis of the Egyptians is spread by the house fly. 

 The experiments of Grassi show that the eggs of Taenia, Tricho- 

 cephalus and Oxyuris pass uninjured through the alimentary tract 

 of flies. 



Methods of carrying diseases. The most common and danger- 

 ous infections conveyed by the house fly are typhoid fever, other 

 intestinal disorders, including those affecting young children, and 

 tuberculosis. Typhoid germs may be discharged from the human 

 system several weeks before diagnosis is possible, continue in num- 

 bers 6 to 8 weeks after apparent recovery, and in exceptional cases 

 may persist during a period of several years. There are authentic 

 records of a patient distributing these germs for 17 years and being 

 the incipient cause of 13 cases during 14 years of that period. Even 

 the urine of patients may contain active typhoid bacilli. Further- 

 more, Dr M. A. Veeder of Lyons cites a case where typhoid fever 

 was perpetuated from year to year in a locality, ascribing it to a 

 physician recommending the burial of all typhoid excreta and the 



