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PUBLIC RECORD OFFICE

Reference

C.O.885

PUBLIC RECORD OFFICE, LONDON

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3. Collections of stagnant water: As far as practicable, these, when found exist- ing, should be treated in one or other of the ways advised. On the higher ground of Mombasa it is rather infrequent to find pools of water which remain for more than a very short time. Should any such be found, the Medical Officer might report the matter to the Sub-Commissioner, and at the same time state what he considers to be the best method of dealing with them, e.g., whether he considers that the water could be easily drained away, as in the case of shallow pools, or whether it would be better to fill it up, or to apply some agent to the surface of the water which would kill the larvæ. There is a considerable collection of water in the neighbourhood of Makupa which contains anopheles' larvæ. This is referred to in one of the reports, but I think that the question of the eradication of or otherwise dealing with this "lake" can be left until other means of prophylaxis have been given a trial.

4. As much jungle as possible should be cleared away from the vicinity of the houses. Prison labour might be employed for this purpose.

5. I consider that it would be advisable to have a Notice, such as that prepared by Dr. Manson, or the one by Sir Michael Foster, hung up in the quarters of each official, and also in all Government offices. Perhaps the one by Dr. Manson, entitled 'Malaria: Its Cause and Prevention," is the more preferable for this purpose, as it goes into greater detail, and might thus cause more interest to be taken in the minutia of the prophylaxis of malaria. Should this suggestion meet with approval, a supply of this Notice might be ordered for distribution to the officials in this station.

6. The suggestions contained in paragraphs (f.), (g.), (h.), (i.), in the Circular of the 20th April, 1901, from the Colonial Office, might be adopted with advantage.

7. Dr. Manзon and others, notably Dr. Koch, lay stress on the value of quinine as a preventive of malaria. I concur in this, and I would recommend that those who may chance to be at any time exposed to conditions favourable for acquiring malaria ́should avail themselves of this weapon. Ten grains, in such circumstances, taken on alternate days, would suffice. In some cases it might be sufficient to give 15 grains on two successive days. Into further details I do not go here, as the advice of a medical officer should be taken as to the particular set of circumstances in each case, and as to the kind of prophylactic treatment by quinine which is indicated.

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8. The above considerations are meant for general adoption in the district of Mombasa; but, in the case of the houses referred to as being in too great proximity to native dwellings, and the house on the Kilindini road, which is surrounded by numerous mango-trees and others which harbour mosquitoes, I think that suggestion (b.) of the Circular from the Colonial Office might be adopted with advantage by affix- ing fine-meshed wire gauze to the windows and doors of the rooms in use as bedrooms. In the case of the doors, the wire should be.stretched across the framic-work and nailed on; but, in order that the door should remain constantly shut, it ought to be made in such a way as to allow of its closing automatically. The windows might be treated similarly, or preferably, the gauze nailed on to the frames. The reports re- commend iron-wire gauze. I should, however, suggest that fine brass-wire gauze would be the better; although its initial cost is greater, this is more than compensated for by the length of time it lasts longer than the iron-wire gauze, as this is so prone to I enclose a specimen of the brass-wire gauze. Its cost is about 4d. per square

rust.

foot, but I think a finer mesh than this is required.

9. The destruction of mosquitoes by special means: As a subsidiary means, this is an agent in prophylaxis which it is as well to have at hand for use in certain circum- stances. The difficulty is in selecting a culicicide which will be efficient without being of too powerful a nature for use conveniently. Here I cannot do better than quote from a recent work by the Director of the Hygienic Institute of Rome, Professor Celli. He says:-

After performing the above comparative laboratory experiments last summer, we made numerous experiments on a large scale to protect houses, and especially bed- rooms, from Mosquitoes, and we have found that a powder composed of larvicide, un- expanded, flowers of chrysanthemums and valerian root to be the best for the purpose. Burning one or two tablespoonfuls of it in the evening, in a room of 36 to 40 cubic metres, stupefied the mosquitoes until morning; by burning larger quantities, they were found dead in the morning on the windows and floor. The fumes of this powder are not disagreeable to most people, and if valerian be unpleasant to some, it can be omitted, or its odour can be masked.

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"It is to be particularly remembered that in general all these odours, fumes, and gases must completely saturate a room in order to kill the mosquitoes."

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Again, "By cultivating chrysanthemum or pyrethrum plants largely, from the unexpanded flowers of which the powders are made, it is very probable that one will succeed in making the malarious place itself produce a substance which is capable of destroying the mosquitoes which infest it."

"Larvicide" is a substance derived from coal-tar, and it is not poisonous to man or to mammals. Very weak solutions of it are sufficient to destroy the young larvæ rapidly. A solution of 1 part in 2,000 destroys them in two hours, according to Professor Celli, and 1 part in 8,000 in four hours. Consequently, this is a sub- stance which would be useful both for the purpose of destroying the adult mosquitoes when they have, accidentally or otherwise, gained access to the rooms of a house; and, secondly, for destroying larvæ in collections of water, should this at any time become necessary.

The cost of larvicide does not appear to be great, and the quantity requisite to destroy the larvæ in 1,000 gallons of water would not, I gather, cost more than a few pence.

I would suggest that, when I am on leave, I might make further inquiry into this question of the powder mentioned above, both as regards its price and the possi- bility of obtaining it, should it be decided to order it.

Finally, on the strength of the results recorded by Celli, I think it would be reasonable to recommend the cultivation of chrysanthemums and pyrethrum plants by all who are possessed of the requisite space around their houses or quarters.

SIR,

I have, &c.,

J. T. C. JOHNSON,

F.R.C.S.

Dr. RADFORD to Dr. MACDONALD.

Nairobi, October 16, 1901.

I HAVE the honour to acknowledge the receipt of your letter re malarią. With regard to the various means suggested in the publications forwarded to me for the mitigation or prevention of malaria, I question whether they could with much hope of success be applied to Nairobi.

This town is built on a plain at the foot of hills, and its natural drainage is most inefficient. This suffices, it is true, to carry off the surplus rainfall in course of time, but the water collects in innumerable puddles, depressions, and pits over a very ex- tended area, and remains there for weeks on end.

These natural breeding-grounds for mosquitoes are increased by the removal of soil, &c., used in constructing the Uganda Railway; pits are formed on both sides of the line. Here water lies for long periods, its retention being favoured by the hardness of the soil, which is generally rock a few feet or inches below the surface.

These pits are daily increasing in magnitude and numbers as the local authorities are removing soil for road construction. These roads are an absolute necessity, as the whole district is flooded during and after the rain, but it is a matter of regret that more care has not been exercised in choosing suitable places for the excavation of soil where these pits, &c., could be drained into the Nairobi River (the natural outfall).

The Nairobi River flows through a swamp for 2 miles in the middle of the town- ship; the fall of the water is considerably impeded by papyrus, rushes, and vegetation. This should be drained at once, and the water confined in definite channels.

In the river, water channels, pools, pits, &c., the anopheles funestus is found (vide Report by Dr. C. W. Daniels, 21st October, 1900).

On the Government establishing the head-quarters of the province here after the advent of the Uganda Railway some years ago, little care or discrimination appears to have been exercised in choosing suitable sites for Government buildings, i.e., barracks, officers' houses, and offices, &c., and in some instances little or nothing has been done to clear the ground around about.

I would point out that Nairobi, in my opinion, is fairly healthy, though malaria is by no means uncommon, and the "small" black" mosquito is found everywhere where water congregates. It is an interesting fact, and worthy of some amount of investigation, that the Europeans who have resided near, or who have known Nairobi for the last six years, confidently affirm that the mosquito has increased in numbers since the advent of the railway.

There are at present no densely-populated native quarters (native=African natives)-

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