26)> 



SANITMiV NOTKS 



Malarial 

 oiiibrfak in 

 Khartoiiin 

 North 



Additions to 

 the " irri^tion 

 rules" 



town is thifiitened, and tlicii- can be no doubt that if work stopped for two niontlis, 

 cases of locally-acquired malaria would soon be notified, and everyone would be complaining 

 of the voraciousness of Stegomyia throughout the day and the blood-thirstiness and 

 insatiable appetite of Giiiex fatujann in the watches of the night. 



One lias mentioned the farm at Khartoum North, both here and in previous Reports, 

 and it may l)e well to consider a small outbreak of malaria due entirely to faulty conditions 

 prevailing there, and which, as already stated ^/w'/c 252^, escaped detection for a time. 



If one turns to paijv '211 and looks at the Table, it will be evident that practically all 

 the cases of locally-acquired malaria occurred at a certain period of the year. The reason 

 is not far to seek and is due to the above-mentioned infestation. Moreover, the great 

 majority of the cases occurred either amongst British troops housed in barracks on the 

 other side of the river from the farm, or in persons living not far from the boundary of the 

 irrigated area. It is, however, rather the persistence of the mosquito infection to which 

 I would direct attention. Fig. 88 shows how the land at the farm is laid out, at what 

 parts of it infection occurred and at what dates C. (Culox) and A. (Anophelines) were 

 found. It will be seen that the infection ranged from January 30, 1910, the day 

 on which special attention was directed to the farm as a result of the illness of the 

 inspector (page 252), to June 5, 1910, and this despite every effort to stamp it out. The 

 figures, however, it must be remembered, do not refer to places where mosquitoes bred out, 

 but merely to pools, etc., in which the larvie or pupae were found, a very different matter. 

 Indeed, it was very rarely that the water stages of the insect got the length of becoming 

 pupse for the inspections were numerous and rigorous. There was no way of getting at the 

 imagines, of which presumably there was not a great number. Indeed, not a single 

 adult P. costalis was ever found at the British Barracks, despite the nine cases of malaria 

 occurring amongst the troops. Undoubtedly, some of these infections took place at Buri, 

 to the east of the barracks, at the places where anophelines bred out in the river pools, 

 a locality eventually put out of bounds for the soldiers. 



Malaria cases ceased to occur although the infection of the farm continued. It must 

 be remembered that, although, as Ross has pointed out, there must be, in all probability, a 

 considerable number of Culices about before they constitute themselves a nuisance, a single 

 infected anopheline may be quite sufficient to give rise to several cases of malaria. At the 

 same time, as there nmst be a source of infection, and as the mosquito must find that 

 source in order to become infected, it is probable that, in most cases, if malaria is to 

 be, in any sense of the word, epidemic, anophelines must be present in fair numbers. Hence 

 a few female Pyretoplionis flitting hither and thither and seeking, desperately, water- 

 collections wherein to lay their eggs need not be regarded with alarm provided such 

 water-collections are under scrutiny. It is, however, a totally different affair if there is 

 no routine and efficient inspection, and a little consideration of these facts and of the plan, 

 should impress upon all concerned not only that constant and unremitting vigilance is 

 essential, but the absolute necessity for the establishment of dry zones. 



What may be called the irrigation rules have already been stated,' but when, at a 

 later period, the above-mentioned farm changed hands, re-infection again occurred, and 

 there was a recurrence of malaria amongst British troops, fortunately on a very small 

 scale, it was found advisable to supplement the rules by a few additional regulations. 

 As these are of practical interest I give them here, though in certain particulars they 

 overlap the more general instructions : — 



Thirrl Report, IVfUcotne Tropical lUsearch Ln/mralorU.i, 191)8, p. 67 



