Research into the trypanosomiasis problem : a critical consideration of suggested measures : with discussion and report of the Glossina Sub-Committee / by Warrington Yorke.

  • Warrington Yorke
Date:
[1920]
Catalogue details

Licence: Public Domain Mark

Credit: Research into the trypanosomiasis problem : a critical consideration of suggested measures : with discussion and report of the Glossina Sub-Committee / by Warrington Yorke. Source: Wellcome Collection.

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    presented very few objective signs, but in general they lived only a few months. Occasion¬ ally, however, a patient is more resistant, and one native definitely proved to be infected with T. rhodesiense is still alive and in a state of apparent good health a year later.’’ Pro¬ fessor Yorke has told us to-night that, in his opinion, the result of the heroic experiment by Taute and Huber “ might well have been different ” if the inoculations “ had been made from the blood of an infected man, instead of from infected horses and mules,” owing to the enhanced virulence of the parasite that might have been expected under such conditions. On the other hand, in the Luangwa Valley, as on the shores of Victoria Nyanza, infected blood may often be conveyed by tsetse-flies “ mechanically from one native to another,” a process which, as Duke has pointed out, is not incompatible with increase of virulence on the part of the parasite. Professor Yokke himself will admit that he cannot have it both ways. If the trypanosome taken from man is more dangerous to man than that from animals, I venture to maintain that this native, who had trypano¬ somes in his blood, but was still apparently well at the end of a year, and may be alive now for all we know, is, if he be not under lock and key, far more dangerous to the surrounding inhabitants than very many antelopes. Dr. Aylmer May (Principal Medical Officer of Northern Rhodesia), in the course of his examination before Lord Desart’s Committee, stated, in reply to questions put to him by the Chairman, that 40,000 natives in Northern Rhodesia had been examined for sleeping sickness, that the disease was not increasing there, and that there were fewer cases than in the previous year (120 in all in four and a half years, since 1909). I asked Dr. May in how many instances out of the 40,000 natives examined a blood examination had been made, and he replied, “ Roughly, in about 20 per cent.” In other words, while but 40,000 out of 100,000 natives in the sleeping sickness area were examined for sleeping sickness at all, it was only in the case of 8,000 individuals that an actual blood examination was made. Does Dr. Yorke believe that this examination of the blood of 8,000 out of 100,000 people is sufficient to prove that not one of the remaining 92,000 had trypanosomes in the blood ? And does he maintain that his native, who was alive and well a year after being proved infected, was the only exception to the rule in Tropical Africa, and that he was so unfortunate as to come upon that single exception ? Professor Yorke, when himself examined before the Departmental Committee, and questioned about the result of Taute’s original experiment, to which reference has been made to-night, would not admit that it proved anything more than that Taute himself was immune to the particular trypanosome concerned. But Professor Yorke proceeded to add : “ If he had inoculated one hundred human beings the result would have been very different.” Here, in this paper, we are told that Taute and Huber, in 1919, inoculated themselves and 129 natives, i.e., they made 131 experiments. Results were uniformly negative, and Dr. Yorke now says that more than 130 experiments would have to be conducted before one could obtain positive results. I may be unduly obtuse, but I cannot see that, in this matter, Professor Yorke’s attitude is very different from that popularly known as “ Heads, I win ; tails, you lose ! ” Dr. B. Blacklock : There are one or two points I would like to ask about. Professor Yorke mentions the recommendations of the French Commission, that pigs should be used, being resistant animals, as a screen to protect native villages from attacks of glossina and from being infected. The connection of the pig with the fly has been wrorked out by several observers. In the Island of Principe, the Portuguese Commission said that the absence of the tsetse fly from the Southern part of the Island was due to the absence of the pig in that part. Further observations were recorded by Macfie from Nigeria, and he quotes Dr. Foran on the relationship between G. tachinoides and the pig. Pigs are known to be naturally infected with trypanosomes, as has been proved on many occasions. In Principe and the Belgian Congo, pigs were heavily infected with trypanosomes, and in Principe a cattle trypanosome of a polymorphic kind was inoculated into a pig successfully. The trypanosome appeared to be like T. gambiense. Inoculations have been done into pigs wflth animal and human trypanosomes, and in Beck’s gambiense case the pig remained infective six weeks. The most interesting experiment of this kind
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