22 



MOSQUITO WORK IN KHARTOUM, ETC. 



ridiculed. This was the more to be regi'etted as there is no doubt that mosquitoes 

 can be banished from all rlie steamers if a little care and troulsle were taken. 

 Mr. Beadnell, of the Geological Survey, carried out these sim})le methods on the 

 s.s. " Nubia," and practically cleared her of mosiiuitoes, so that for the first time he 

 was able to sleep below in comfort. A gi'eat impi'ovement also resulted in the case 

 of the gunboat " Zaiir," in wliich I went to Dueim and found to be simply 

 swarming with adult Culices and their lar\-te, while these measures absolutely 

 prevented any mosquitoes breeding out on board the s.s. " Amka " during a period of 

 nearly two months, the greater part of which was passed in regions swarming with 

 these winged pests. Latterly, I am glad to say, the engineers have been imjjressed 

 with the necessity of doing all in their poAver to aid the brigade. This is the 

 more necessary as it is easy for the steamers to infect the town and thus spoil much 

 of the work done and render it futile. I am certain that this has occuiTcd in many 

 instances for reasons which wiU be stated. 



The men of the brigade also paid some attention to the killing and captui'ing 

 of adult mosquitoes, but without much success, as most of the Culices live in the 

 wells and are not easily obtained, while it was impossible for the men to go 

 round and catch mosquitoes in Mohammedan households. A good many Ano- 

 phelines and Stegomyia were, however, captured, and in the case of the former 

 I made an effort by dissecting the females to detemiine the proportion harbouring 

 the zygotes of the malarial parasite. As Daniels ' has pointed out, this method 

 is only of value when the mosquitoes are selected fi'om different houses and 

 places in equal proportion owing to the great variations which occur in this 

 jDroportion in adjoining houses and at different times. iVs he says, the niunber 

 of infected mosquitoes is the real test, and the number of Anophelines that bite 

 a man ])er liour is also required. Consequently, such examinations as were 

 performed ptissessed little value, and, indeed, it soon became difficult to secure 

 material, chiefly because, as the result of the lirigade work, Anophelines became a 

 rarity. It was a case of kiUing the geese wliich laid the necessary, if not the 

 golden, eggs. Of greater importance was the preservation of specimens of 

 captured eggs, larva, and pupa3 of aU the genera found, as these pi'oved valuable 

 object lessons to officers and others proceeding up-country. Several have thus 

 learned for the first time to recognise the appearance of the water-stages of the 

 mosquito. Mr. Cross, of the s.s. " Gordon Pasha," made a point of bringing back 

 specimens from his trips up the White Nile. 



On the whole, Khartoum may be said to have had a moderate " endemic 

 index." There were not a vast number of malaria-canying mosquitoes, but thei'e 

 were many people who harboured the malarial parasite and m;iny more suscep- 

 tible to infection. 



Tlie results of the work of the bi'igade are interesting and instinictive in 

 several directions. In the first place they have shown the distribution of eacli 

 of the three main genera. 



' Daniels, " Laboratory Studies in Tropical Medicine " 



