The Milroy lectures on kala-azar, delivered before the Royal College of Physicians of London. Lecture III, The life-history of the parasite, mode of infection, and prophylaxis / by Leonard Rogers.

  • Leonard Rogers
Date:
1907
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Licence: Public Domain Mark

Credit: The Milroy lectures on kala-azar, delivered before the Royal College of Physicians of London. Lecture III, The life-history of the parasite, mode of infection, and prophylaxis / by Leonard Rogers. Source: Wellcome Collection.

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    Mevicat Jourwat — anthropoid apes have not been experimented upon owing to the difficulty and expense of obtaining them, one orang-outang which I got for the purpose having died too soon to enable this point to be settled. As sufficiently numerous feeding experiments with such insects to be of any value require much time, Ispent in Assam all the leave I could obtain last year when the temperature conditions were favourable for this purpose; but, although I examined blood from the stomachs of over 200 bugs fed on kala-azar patients with low powers in a fresh condition for active flagellate forms, | had met with no success when I had to stop on account of my eyes, and have only been able to find time since to examine a few of the stained slides then made. This failure was disappointing, but the time available for the work was so short that I did not regard the negative result as in any way invalidating my theory; I was therefore much pleased to learn several months later that W. 8. Patton, I.M.S., had been placed on special duty to work on similar lines, and still more when it was announced in the Indian Medical Gazette that he had obtained some development of the kala-azar parasites in the stomachs of bedbugs, but not in those of mosquitos, ticks (with which S. R. Christophers had previously obtained negative results) or lice. While on a visit to Madras last Christmas holidays Dr. Patton kindly showed me his specimens, which clearly contained the early stages of the development with the appearance of the eosin body, and_in one of his drawings a short flagellum was also apparent. They struck me as being very similar to the scanty development I obtained before using acidified media, and gave me the impression that the conditions were not those most favourable to the process; and on inquiry I found that attention had not been paid to the obtaining the most favourable tempera- ture for the development, so I urged him to do as many feeding experiments as possible during the then more favourable cold season, when the optimum temperature could be obtained. The result has fully substantiated my opinion, for within three weeks Patton wrote to me: “JT have got the complete cycle of the parasite up to completely-developed flagellates”; and added, “There is no shadow of doubt that the bedbug transmits the disease.” Much doubtless remains to be done in this direction in.order to ascertain exactly in what form the parasite is again inoculated into the human subject, for the long time during which the infection clings to houses points to the possibility of it being transmitted through the progeny of the first affected bugs, just as occurs in the case of the piroplasma of cattle and dogs; hence that the ovaries and salivary glands should be carefully examined in fed insects for further stages of the para- site. Nevertheless, our knowledge of the life-history of the kala-azar organism is now sufficiently known to enable the facts to be made practical use of in the prophylaxis of the disease, which is the last portion of my subject remaining to be considered. THE PROPHYLAXIS OF KALA-AZAR, I have already mentioned the partial success of moving infected villages to new sites but a short distance away, which, taken with the strong evidence I collected in 1897 as to the infection being a house one, appeared to me to afford the most promising basis for preventive measures, Finding also that over a year before I went to Assam Dr. Dodds Price, suspecting the disease to be infectious, had placed 150 out of 200 freshly-imported coolies in newly-built lines of houses, while the remaining 50 had to be accommodated in infected lines for want of room, I got him to work out the results of this measure. It was thus ascertained that although none of the 150 in the new lines had suffered from kala-azar during two years they had been on this badly-infected tea garden, yet no less than 8, or 16 per cent., of those placed in the old lines were already dead of the disease, and that, too, in spite of the fact that the new lines were but 300 yards from the old ones, a distance insufficient to prevent the spread of malaria through the agency of mosquitos. This very important result obtained by Dr. Price encouraged me to suggest the further step of moving all the healthy people out of infected lines to houses on a new site, no person, however, being taken from an infected hut in consequence of the impossibility at that time of 8 differentiating the early stages of kala-azar from ordinary malarial fever. This plan was carried out by Dr. Price in the case of a coolie line which was so badly infected that no less than 144 out of 240 souls were either actually suffering from kala-azar or had cases in their households, leaving only 96 who could be moved to the new site, 5 of whom were very shortly afterwards sent back on account of their developing fever. A large number of fresh coolies were also drafted into these new lines, so that eighteen months later it contained 416 souls, among whom not a single case of kala azar had occurred, a statement which happily remains true at the present time, ten years: after they were occupied. In marked contrast with this result is the fact that of 60 coolies who refused to move out of the infected lines no less than 20, or one-third, were attacked within the eighteen months, and a year ago they had nearly all been carried off by the disease, although their houses were only 400. yards from the new ones which remained healthy. This experiment was so conclusive that it has since been often repeated with uniformly good results, so that the disease is no longer as dreaded as it used to be by tea planters in the Nowgong district. In slightly- infected lines only the affected households were segre- gated and their houses burnt, this measure being also of value, although less effective than the former one. It is only in the few remaining old lines that the infection lingers at the present time, and I am glad of this oppor- tunity of saying that Dr. Dodds Price deserves the greatest possible credit for initiating and successfully carrying out these measures, especially as he has been too modest to claim it himself. It is not too much to say that it is now certain that this awful scourge can be robbed of most of its terrors whenever it is possible fully to carry out segre- gation measures, as on tea estates, while their success has encouraged the application of the same principles in dealing with the spread in villages, as far as they are practicable in that case. MEASURES TO CHECK THE SPREAD OF KALA-AZAR IN THE VILLAGES. It was not possible to carry out such complete measures as the above in the infected villages, but the following recommendations of mine proved successful in preventing the spread of the disease into the eastern half of the Brahmaputra Valley, as already described. In the first place, a pamphlet in the vernacular was widely distributed, explaining, in simple language, the manner in which the infection was spread and the precautiors necessary to prevent its introduction into unaffected places, and by thus putting the people on their guard against the insidious invasion cf the disease they were often enabled to keep it at bay without having to learn the lesson by bitter experience. In the second place, assistance was given by the Government to already infected villages to remove to a new site, the infected persons being, as far as possible, accommodated in a separate place. It may, then, be fairly claimed that much practical good resulted from my inquiries of 1896-7, both in the preven- tion of the further spread of the disease up the Assam Valley and also in its being practically stamped out of the Nowgong tea gardens, and it is worthy of note that all this was accomplished before the exact nature of the disease was ascertained by the discovery of the parasite in 1903. Moreover, the success of the measures based on the theory that the disease was essentially a house one is readily accounted for by the bug theory of infection, which has now received such strong experimental support. THE DESTRUCTION OF BEDBUGS AS A PROPHYLACTIC MEASURE. al Just a year ago, several months before Dr. Patton's successful feeding experiments, I arranged with Dr. Dodds Price for him to try the effect of repeated attempts to destroy all forms of insect life in the infected houses and those immediately around them in acoolie line in which kala-azar cases continued to arise each cold weather, leaving a second slightly-infected one as acontrol. The houses were fumigated with burning sulphur, the beds thoroughly washed with strong boiling carbolic lotion, the clothes either boiled in the same solution or destroyed, while the blankets were all burnt as being most likely to harbour bugs, new clothes and blankets being supplied. In the’ line which was thus treated 6 cases had occurred during
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