20 MOSQUITO WORK IN KHARTOUM, ETC.

Use of petroleum

Mosquito Brigade work

Fortunately, in Khartoum we have not to deal with any swamps, ditches, permanent pools in the streets or near the houses, empty cans, old bottles, broken crockery or other receptacles containing water for any length of time ; at least, there were none such last year. It is possible that they might have to be considered during a very wet summer, but the rainfall of 1903 was trifling. As a result the labours of the brigade have been limited, and the small staff has so far sufficed. Major Ross 1 recommends refined petroleum or eucalyptus oil for

the “ training ” of well waters, but, after careful enquiry it was deemed better to employ crude petroleum, not only because it was cheaper, but because com¬ paratively little of the well water is used for drinking purposes, the native portion of the population preferring to use water direct from the Blue Nile. Latterly, as a considerable quantity of the refined petroleum had been stocked, a mixture of crude and refined has been employed. The former appears to be the more efficacious, as it forms a denser film and one which lasts longer. The well water in Khartoum is for the most part reserved for washing, cooking, and the use of animals. It was evident that the oiling of the wells would entail some hardship on their owners, but the above fact shows, what indeed proved to be the case, that it could be done without producing any great outcry. The user of an infected and oiled well generally managed to easily satisfy his wants from a neighbouring uninfected and untreated water supply.

Crude petroleum, as stated, is very effectual if properly applied, and, moreover, makes the water so unsightly that none would touch it, and thus there was little risk of any poisoning from water so treated. As a matter of fact, no such accident has been reported, and the plan adopted was as follows :—

The men constituting the brigade began every morning to visit system¬ atically all the water collections in the town, beginning on the river front and working backwards day by day till the whole town had been explored. They were provided with wide-mouthed bottles for taking samples, and instructed how best to proceed. A cup-shaped apparatus of fine wire gauze was also employed, but the bottles were found quite as efficient, especially when the men were made to take three or four samples from different parts of the surface of every well watei where the first dip proved negative. In the case of other water collections Durham’s larva collecting spoon and tin,2 recently introduced, have been found to answer admirably. In the afternoons, under the charge of Mr. Newlove, the men again went their rounds, the water collections were re-inspected, and any found to be infected were thoroughly oiled. In the case of wells, observations showed that m the great majority we had to deal with a surface area of from

1^ to 13 square feet. Roughly speaking, about one pint of the crude petroleum was employed per well. This amount was probably in excess of that actually lequiied, but by using it a reliable film was obtained. Syringes, though good m the case of pools, were no use for wells, and it was found best to simply pour the oil straight down upon the water, which, as a rule, was found at a

1 Ross. “ Mosquito Brigades ” 2 Journal of Tropical Medicine, 1/10/03