Minutes of evidence taken by the Departmental Committee on Sleeping Sickness.
- Great Britain. Colonial Office. Committee on Sleeping Sickness.
- Date:
- 1914
Licence: Public Domain Mark
Credit: Minutes of evidence taken by the Departmental Committee on Sleeping Sickness. Source: Wellcome Collection.
16/346 (page 6)
![10 October 1913.] [ Continued. here, but J think you may take it that gambiense is a very mild disease in goats or sheep, and that few or none of them will die of it. You will find the try- panosome in their blood for a good long time if you look hard enough for it, but rhodesiense or bruced is a fairly fatal disease to goats and sheep. 90. Would your reply apply to the cattle as well ? —Yes, I should say gambiense has a very slight effect upon cattle. Of course bruced or rhodesiense is not a very fatal disease to cattle either, a large number of them recover but it is a much more dangerous disease for cattle than gambiense. It is so difficult, cattle being expensive things, to experiment upon a sufficient number of the animals to get a good idea, but there is no doubt that a good big percentage of cattle will recover from brucei under laboratory conditions, whereas gambiense would have little or no effect upon them. If you get gambiense straight away from a man it is very difficult to infect the ordinary animals like dogs or rats; you require to inoculate them again and again before they take at all. 91. (Mr. Buzton.) I only want to ask you two questions. Assuming this experiment to be tried, I understand that one of the most important and instructive things that might be evolved from it would be to ascertain the ratio of infected and non- infected flies after a certain period; but would not the activity of these flies (and they seem to make light of travelling 30 miles an hour from what you say) destroy the value of that, because they would invade your 10-mile area, make nothing of it, and be continually invading it?—It is very difficult to know what these little creatures will do unless you try an experiment; it is a difficult thing for a man to know himself, but when man tries to get behind the brain or the mind of a fly it is still more difficult. I could not say what the flies will do at all. 92. The morsitans is a very active fly ?—Very active; it can fly with great rapidity, but whether he would go five miles, or three miles, or four miles to get a feed and then come back again to his ordinary haunts is a matter for experiment. I expect if you fenced in this area and drove the big game out, there would be no fly left except round the edges. 93. There would be nothing to tempt them in, you think ?—That is so; where the carcase is there will the flies be gathered together. 94. It struck me, as a non-informed layman, as a most curious anomaly that you have not a repetition of the epidemic in Nyasaland that you have had in Uganda. You have all the conditions, it would seem to me from what you have told us this morning, very interesting facts—a large native population, a vast number of wild animals infected with the trypanosome and the fly continually moving about. You have told us you have seen as many as 200 flies feeding on the back of a native. What strikes me as very difficult to account for is that you have not had already a tremendous epidemic of sleeping sickness. Can you differentiate between the two countries in your mind ? Can you surmise why it is that there should be comparatively very few cases in Nyasaland and a tre- mendous loss of life in Uganda ?—You are dealing with two different diseases altogether. In the one case you are killing off the natives in Uganda with a machine gun, and in the other case you are knocking them down one by one with a big elephant gun perhaps. They are two different diseases ; man is very susceptible to the one and not very susceptible to the other. He is susceptible to the Congo sleeping sickness; he is not at all susceptible to the Nyasaland sleeping sickness. He has had the Nyasaland sleeping sickness for thousands of years ; he has been born and bred among it. The blood of a man has no deleterious effect on Trypanosoma gambiense; the blood or serum of a man has a very deleterious effect on Trypanosoma brucei vel rhodesiense. If you put Trypanosoma gambiense under the skin of a man that man will certainly get the disease, but if you put Trypanosoma brucei vel rhodesiense under the skin the blood of the man will probably kill off the trypanosome before it is able to multiply. That is the reason why cases of the disease in tbe one country are few and far between, and in the other country why it has knocked the men down by hundreds of thousands. 95. I follow that, but may we take it that to a large extent, or in the case of a great many individuals, they are practically immune from the disease in Nyasa- land? If we have 200 flies, a proportion of which are infected, biting a man simultaneously, what is the reason he does not take the disease for a certainty ?—I have been trying to explain that the blood of man has avery deleterious or killing off effect on the Trypano- soma brucet or rhodesiense. If you take a rat full of Trypanosoma rhodesiense or brucei and put a small quantity of haman serum under the skin of that rat you will kill off all the Trypanosoma brucez in that rat or a great number in a very short time, whereas if you take another rat of the same description and with the same number of trypanosomes, but the trypanosomes being Trypanosoma gambiense, the injection of the human serum will have no effect upon them. 96. Is not that another way of saying that the human animal, or the native human animal, has become for one reason or another more or less immune in the course of centuries ?—We people who work at these things by experiment seldom or never try to answer these difficult questions. You are talking about a person having become immune. I would say that man had never been anything else. I should say that very probably at first (and it is a question of evolution) Trypanosoma gambiense and brucec were the same, but at a particular time and place there were a large number of natives about and the flies fed a great deal on the natives and bruced got into a man and lived there; on account of some peculiarity about this particular brucei he was able to live in this man and multiply. Then the flies took it from that man and it went on for many generations and after several thousands of years gambiense changed from brucei so much that it could live with ease and comfort in the blood of man without any danger of being killed off, whereas the original stock from which it came, brucez, still retained the original habit of being killed off by means of the blood serum of man; but these things are so much in the clouds and in the region of specula- tion that we very seldom spend any time over them. 97. (Sir William Leishman.) I will not trouble you very much, but I would like to ask one or two points about your work with flies in captivity. How long will a fly. go without blood ?—Four or five days. I think if you kept some flies they might live 12 or 14 days if you absolutely starved them to death after having given them a big feed the first day, but I do not think there would be many living on the fifteenth day. It would dependa great deal on the temperature and the humidity of the air how long they lived. 98. You have bred a lot of flies from pupx; have you ever succeeded in breeding the second generation in captivity P—Yes, but not to any great extent. 99. Have any of the second generation been the descendants of infected flies which you have proved to be infected yourself ?—Yes. 100. Have you had any results from that—I am talking of morsitans ?—I was thinking you were talking about palpalis. We have had thousands and thousands of palpalis pup. In fact the natives brought up 7,000 pup of Glossina palpalis in one day but you could offer a sovereign for every wild pupa of morsitans without getting one, so that we had far more laboratory-bred flies to work with in palpalis than in morsitans. It is a dificult matter to get the morsitans pupe and I was talking about palpalis when I said we had them. 101. With palpalis have you any observations on the second generation of flies coming from a fly you have known to be infected ?—The only observation is _ that we never found these laboratory-bred flies infected ; I think that has been proved as well as we can prove a thing, that the fly does not transmit the parasite to its offspring like a tick. 102. Have you confirmed the work on the influence of temperature on the infectivity of the fly? In certain seasons do you get their infectivity more readily than in others ?— Yes, it came out in the ordinary course of work; I do not think we studied it for itself but it came out in the ordinary course of](https://iiif.wellcomecollection.org/image/b32178104_0016.jp2/full/800%2C/0/default.jpg)
