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PUBLIC RECORD OFFICE

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7869

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No. 10.

NYASALAND.

THE ROYAL SOCIETY to COLONIAL OFFICE.

(Received 7 March, 1913.)

[Answered by No. 16.]

SIR,

Burlington House, London, W., 4th March, 1913. Ar a recent meeting of the Tropical Diseases Committee of the Royal Society I had the opportunity of laying before the Committee the opinions recently expressed at a meeting of the Entomological Research Committee at the Colonial Office, together with the views of Sir W. H. Manning, lately Governor of Nyasaland, with regard to the further conduct of the investigation now in progress there under the direction of the Royal Society's Committee. In particular, the Committee dis- cussed the proposals by Sir David Bruce, which have been before the Secretary of State for some time past, for an experiment on a large scale of the enclosure of a tract of country and destruction of the wild game therein in the sleeping sickness proclaimed area of Nyasaland, with the object of ascertaining the value of game destruction as a means of eliminating the flies which have been shown to be the carriers of the infection of trypanosome diseases in Nyasaland. After a full discussion and consideration of Sir David Bruce's proposals and the criticisms which had been made upon them, the Committee arrived at the conclusion that an experi- ment of the nature indicated by Sir David Bruce offers the only practical means of solving the question referred to this Commission at the time of its appointment, namely:

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To conduct an enquiry on the spot into the relation of the African fauna to the maintenance and spread of human trypanosomiasis and, secon- darily, to other trypanosome diseases of domestic animals."

The Committee therefore desire to suggest to the Secretary of State that the experiment proposed be inaugurated with as little delay as possible, and carried out so far as practicable on the lines indicated by Sir David Bruce.

The Committee were informed that an experiment of this nature has been embarked in British South Africa, and they suggest that enquiries should be

upon made as to the steps that are being taken there.

The Committee also discussed the suggestion which I reported to them as having been made at a meeting of the Entomological Research Committee, that an ento- mologist should be employed, independently of the Commission now in Nyasaland, to make a special investigation into the natural history of the infective flies with a view to formulating, if possible, some scheme for their destruction. While agreeing as to the desirability of investigating the bionomics of the tsetse flies in the field, the Committee consider that any such enquiry should be made in collabora- tion with the work of Sir David Bruce's Commission, and they propose to ask Sir David Bruce whether he thinks it advisable to have an entomologist appointed in the place of Dr. Davey resigned, and what the probable cost of such a collateral investigation would be. In the event of such an appointment being found desirable, the Committee would be prepared to lay down the lines of enquiry which should be followed.

I am, &c.,

7934

SIR,

No. 11.

JOHN ROSE BRADFORD,

NYASALAND.

Secretary, R.S.

THE TROPICAL DISEASES BUREAU to COLONIAL OFFICE.

(Received 7 March, 1913.)

Tropical Diseases Bureau, Imperial Institute,

London, S.W., March 7th, 1913.

I HAVE the honour to acknowledge the receipt of your letter of February 14th

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(4668/1913),* with copy of letter and enclosure from Reverend T. F. Daly. Pressure of work has prevented my replying earlier.

2. The Reverend Dr. George Prentice takes exception to statements made by ine in my letter of May 14th, 1912.† Dr. Prentice states that tsetse fly disappeared from South Africa contemporaneously with the disappearance of the big game. This I believe to be in part true. In his opinion it is cause and effect, but I submit there is little justification for this belief. It is as reasonable to suppose that game and tsetse both went from a common cause, e.g., the pressure of civilisation, occupa- tion, or cultivation, or some cause unknown; this is the more probable because, despite Dr. Prentice's dictum to the contrary, tsetse are found apart from big game.

3. We do not know why tsetse disappeared at the time of the rinderpest. Dr. Prentice suggests the obvious reason, but how would he explain the disappear- ance of tsetse in the north-eastern Transvaal, although the big game was never killed off (Stevenson Hamilton, "Bulletin of Entomological Research," July, 1911, pp. 113-118) Major Hamilton writes that the numbers of mpala and wildebeest were little affected by the disease; both these antelopes are fed on by tsetse, but the flies vanished completely.

4. Dr. Prentice objects to the quotations headed tsetse fly and big game that some are antiquated and others contrary to fact. It had never occurred to me that careful natural history observations could become antiquated, by which I take Dr. Prentice to mean obsolete. Moreover, none of the observations are more than ten years old and most are much more recent. Dr. Prentice has not read the extract The about the Mpika and Chinsali divisions of Northern Rhodesia correctly. authors do not say that no tsetse are present, but the reverse; they speak of the concurrent existence of tsetse," and suggest that this may be due to the flies' preference for bush country, which is also that favoured by game.

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5. With regard to Chitambo, I accept Dr. Prentice's statement as correct. does not, however, invalidate that of Kinghorn and Montgomery, for the game may well have appeared in the three years interval. There is no justification for describing any of the statements in the memorandum as loose. I do not know why the statement that British East Africa is the hunter's paradise is introduced, unless it is to throw doubt on the observation cited from that country.

6. Dr. Prentice says that Drs. Kinghorn and Yorke recommend the exter- mination of game. I don't know what opinion these gentlemen have expressed in conversation, but I have before me the monthly magazine of the Incorporated Chamber of Commerce of Liverpool (January, 1913, pp. 4-9), in which a lecture is published by Dr. Yorke on sleeping sickness and big game. There I find the following passage: Whether anything would be gained in this direction by slaughtering the big game is still a moot point; therefore, I will not consider this side of the case, but advocate the advisability of attempting to drive back the game from the neighbourhood of human habitations solely because the big game are the reservoir of the infection." He goes on to recommend a scientific experiment on a large scale and details the lines on which it should be carried out. He continues: Some such decisive experiment as I have outlined is, therefore, urgently required, as even under the most favourable conditions several years must elapse before we should be in a position to recommend definitely that vigorous steps be taken to drive back the big game from the neighbourhood of human settlements on a large scale throughout Tropical Africa."

7. Dr. Prentice states that tsetse cannot subsist in nature on crocodiles, lizards, and snakes. Whether they can or not is uncertain, but it is certain that they have been found where the only vertebrates were these animals and birds. Whether tsetse are in such circumstances harmless to mammals is not proven. The quotation in which reference was made to crocodiles referred to all species of Glossina and not G. morsitans only. It is possible that birds should be regarded as the enemies of tsetse, but the only results of careful investigations have been the finding of remains of tsetse in three birds, one in Uganda and two in Nyasaland. To mention other vertebrates than big game in connection with the food of tsetse is not "to befog the issue," because tsetse do not feed on big game alone. When the blood contained in a large series is examined, the red corpuscles in a good proportion are found to be nucleated, proof positive that it was not derived from mammals. It is true, however, that vertebrates with nucleated red corpuscles have not been found to harbour mammalian trypanosomes.

• No. 7.

↑ No, 24 in [Cd, 6671],

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