28 



MOSQUITO WORK IN KHARTOUM, ETC. 



Extent of 



moscjuito 



destruction 



Future 

 operations 



As regards the second table it is to be noted that it was found impossible, 

 despite eveiy endeavour, to visit eleven Avater collections by the time the statistics 

 were made up, o-\ving to the fact that the houses containing them were closed, 

 and the oAvni-rs alisent. There were over thirty such cases, but by the kind 

 help of the Mudir, to ■whom also my thanks are due for supplying the blank 

 plans, the difficulty was overcome save in these eleven instances. In order to 

 complete the table I have counted six of them as hai'bouring Culex, which is 

 certainly a very fair propoi-tion, judging from what was found elsewhere under 

 parallel conditions. All these houses were in what may be called the "Culex" 

 part of the town. Similarly, in Map No. 3, six unvisited wells are charted, and 

 three of these were considered as being infected. The above figures can only be 

 regarded as being approximately coiTect, and as only applying to the special 

 times at which the examinations were made. The conditions were constantly 

 altering, as the mosquitoes were driven fi'om well to well, and at the time of 

 writing the state of the town is better than the last figures indicate.' Still, these 

 statistics serve to show that very considerable progress has been made. For the 

 sake of argument, let us suppose that the average number of larvae and pupa? 

 in an infected water was one thousand. This is by no means an absurd figure, 

 indeed, I believe it to err on the small side, but even so, taking the first and 

 third tables, a total destruction of 222,000 mosquitoes is indicated, granting that, 

 if left alone, all the lai'vaa and pupa3 would have reached maturity. Nor does 

 this represent in any way the eggs which were checked in their de\-elopment. 



Again, say half of the above were females capable of laying from 200 to 400 

 eggs apiece, a moderate computation, and it will be apparent that the ranks of the 

 Avinged host have undergone enormous depletion. Tliis is further CAadenced by 

 the fact that latterly the infected wells have been found to harbour much smaller 

 numbers of larvae than was the case at fii*st, and by the experiences of residents and 

 visitors. I admit that such statistics as the above savour of guess work, but thev 

 approach the truth, and that trutli is instructive and encouraging. I should think 

 that there are few mosquito-ridden towns which could be so completely cleared 

 as Khartoum, Avhere, as will be evident, the conditions are somewhat specialised. 

 Such a happy result could, however, only be obtained by inci-easing the staff of 

 workers, by constant vigilance, more frequent inspections, and bringing Khartoum 

 North into the field of operations. Colonel Penton, the P.M.O. of the Sudan, has now 

 agi-eed to this being done, so even better results may be looked for in the immediate 

 future, especially as the steamers are to receive special attention. The Manager 

 of the Sudan Development and Exploration Com])any has signified his willing- 

 ness to co-operate in the work of clearing the steamers. Of coui'se if the old 

 type of well were abolished and driven or tube wells substituted, the mosquito 

 would find it \-ery difficvdt to thrive at all in Khartoum, but such a radical and 

 expensive cure would be neither necessary nor justifiable. 



At the time when the Blue Nile was at its highest a considerable tract of land 

 to the south-west of the town was submerged by the danuned u]) \\aters ol the 

 ' In February tbe percentage infected was 10'4, in March only 9'5. Anophelina had disappeared 



