282 THE DISSEMINATION OF OTHER DISEASES BY FLIES 



eyebroAvs of the monkeys. Castellani is of the opinion that yaws 

 is generally transmitted from person to person by direct contact 

 but under certain circumstances it may be conveyed by flies and 

 possibly by other insects. 



Robertson (1908) took about 200 flies which had been captured 

 on yaws lesions and shook them up in sterile water. After stand- 

 ing for twenty-four hours the water was centrifugalized and smears 

 Avere made from the precipitate. In four slides the organism 

 Spirochaeta pertenuis were found. 



In St Lucia, Windward Islands, Nicholls (1912) after studying 

 the disease concluded that the majority of cases of yaws in the 

 West Indies were caused by the inoculation of surface injuries by 

 the fly Oscinis pallipes. This insect feeds on the skin discharges 

 of man and other animals. The flies are very persistent and 

 engorge themselves with pus, blood, serum or sebaceous secretion. 



Leprosy. 



Experiments with flies and human and rat lepra are recorded 

 by Wheny (1908). It was found that such flies as M. domestica, 

 C vomitoria and Lucilia caesar take up enormous quantities of 

 lepra bacilli fi'om the carcase of a leper rat and deposit them with 

 their faeces ; but the bacilli apparently do not multiply in the 

 intestinal tracts of the flies, as the latter are clear of bacilli in less 

 than forty-eight hours. Larvae which have hatched out in the 

 carcase of a leper rat become heavily infected with lepra bacilli. 

 When they are removed and fed upon uninfected meat they pass 

 out most of the lepra bacilli and the flies hatching out ft-om the 

 pupae of these larvae are generally uninfected. If the larvae of 

 C. vomitoria be fed almost continuously on the carcase of a leper 

 rat they remain heavily infested with lepra bacilli and on pupating 

 such heavily infested specimens appear to be incapable of further 

 development. 



A house-fly, M. domestica, caught on the fece of a human leper 

 was found to be infected with lepra bacilli. At the beginning of 

 the observation these were few in number but on the third day 

 more than 1115 lepra-like bacilli were present in each speck 

 deposited. However, only one bacillus was found in the specks 



