326 Lesions Produced by the Bite of the Black-fly 



SUMMARY 



In order to bring the results of the foregoing studies together, 

 the author appends the following resume of the clinical data pre- 

 sented in the first paper. 



The black-fly, Simulium venustum, inflicts a painless bite, with 

 ecchymosis and haemorrhage at the site of puncture. A papulo- 

 vesicular lesion upon an urti canal base slowly develops, the full 

 course of the lesion occupying several days to several weeks. Marked 

 differences in individual reaction occur, but the typical course in- 

 volves four stages. These are, in chronological order, the papular 

 stage, the vesicular or pseudovesicular, the mature vesico-papular or 

 weeping papular stage and the stage of involution terminating in a 

 scar. The papule develops in from 3 to 24 hours. The early pseudo- 

 vesicle develops in 24 to 48 hours. The mature vesico-papular lesion 

 develops by the third to fifth day and may last from a few days to 

 three weeks. Involution is marked by cessation of oozing, subsidence 

 of the papule and scar-like changes at the site of the lesion. The 

 symptoms accompanying this cycle consist of severe localized or 

 diffused pruritus, with some heat and burning in the earlier stages 

 if the oedema is marked. The pruritus appears with the pseudo- 

 vesicular stage and exhibits extraordinary persistence and a marked 

 tendency to periodic spontaneous exacerbation. The flies tend to 

 group their bites and confluence of the developing lesions in such 

 cases may result in extensive cedema with the formation of oozing 

 and crusted plaques. A special tendency on the part of the flies 

 to attack the skin about the cheeks, eyes and the neck along the 

 hair line and behind the ears, is noted. In these sites inflammation 

 and cedema may be extreme. 



A distinctive satellite adeonpathy of the cervical glands develops 

 in the majority of susceptible persons within 48 hours after being 

 bitten in the typical sites. This adenopathy is marked, discrete 

 and painful, the glands often exquisitely tender on pressure. It 

 subsides without suppuration. 



Immunity may be developed to all except the earliest manifesta- 

 tions, by repeated exposures. Such an immunity in natives of an 

 infested locality is usually highly developed. There are also ap- 

 parently seasonal variations in the virulence of the fly and variations 

 in the reaction of the same individual to different bites. 



Constitutional effects were not observed but have been reported. 



