DENGUE CONTROLLED THROUGH MOSQUITOES 305 



The idea that Aedes calopus is concerned in the transmission of dengue has 

 been revived again recently by J. Legendre. He describes an epidemic of dengae 

 at Hanoi during July, August, and September, extending lightly into October, 

 with an occasional isolated case in November. The role of A'edes calopus in 

 the transmission of dengue appeared justified to him, on account of the fact 

 that the epidemiology is an exact reproduction of that of yellow fever. He states 

 that A. calopus bit frequently during the duration of the epidemic and that other 

 culicids were rare during the same period. He argued that the malady stopped 

 at a time when the Aedes calopus became rare. Moreover other biting insects, 

 possibly capable of transmitting the disease, were absent. He offered no experi- 

 mental evidence but the assemblage of facts appeared to him quite sufficient 

 to attract serious attention. To the argument of Legendre the criticism must be 

 made that his general observations can not be accepted against the positive work 

 of Graham and of Ashburn and Craig. It must be pointed out that wherever 

 Aedes calopus is abundant Culex quinquefasciatus is nearly always equally so, 

 relieving the former at night; it would be very strange if such a widely dis- 

 tributed mosquito were absent from Hanoi. Furthermore many of Legendre's 

 observations on the habits of Aedes calopus do not apply to that species and this 

 makes it practically certain that most of the mosquitoes present belonged to other 

 species, probably mostly Culex quinquefasciaius. The mosquitoes mentioned by 

 him as being so abundant early in the season are undoubtedly species of Aedes, 

 similar in habits to those which develop with us in the snow water of early spring 

 and which we have discussed in the chapter on habits of mosquitoes in general. 



E. H. Eoss gives convincing evidence that mosquitoes are a necessary factor 

 in the transmission of dengue. He shows that in Egypt, since the towns of 

 Port Said and Ismailia have been rid of mosquitoes they have escaped the epi- 

 demics of dengue which have invaded the rest of the country. 



" Dengue fever used to be very prevalent in Port Said, as in other parts of 

 Egypt? ■"^P to the year 1905. An epidemic of the disease occurred in the town 

 during the summer of 1904, and in the spring of 1905. This epidemic was part 

 of an infection of all the towns of Egypt, and was most severe. The hospitals 

 were full of cases, and patients actually contracted the disease in them. In 

 Port Said almost everyone suffered from an attack, and the place was regarded 

 as fever-stricken and unhealthy. The town was full of mosquitoes, including 

 two species of Anophelines, Culex fatigans and Stegomyia spp., in abundance. 

 These mosquitoes were breeding in cess-pools under the houses, in basement 

 cellars flooded with sewage, garden fountains, barrels containing water, and 

 were a veritable pest day and night, summer and winter." 



In May, 1906, a campaign against mosquitoes was launched and with the mos- 

 quitoes dengue has disappeared also. 



" During the early part of that year, before the mosquito work began, dengue 

 fever made its appearance as usual. Thirteen cases were treated in the hospital 

 alone during April and May, and then as the mosquitoes disappeared the dis- 

 ease stopped and has not recurred since. In September, 1906, a severe epidemic 

 raged throughout Egypt, beginning at Assouan and running rife in Cairo and 

 Alexandria, It appeared in all the other towns, but Port Said and Ismailia re- 

 mained free from it, no case occurring at either place. During the autumn of 



