Volume 1
Scrub typhus investigations in South East Asia : a report on investigations on scrub typhus by the G.H.Q. (India) Field Typhus Research Team, and the Medical Research Council Field Typhus Team, based on the Scrub Typhus Research Laboratory, South East Asia Command.
- Great Britain. War Office. Scrub Typhus Research Team.
- Date:
- 1947
Licence: Public Domain Mark
Credit: Scrub typhus investigations in South East Asia : a report on investigations on scrub typhus by the G.H.Q. (India) Field Typhus Research Team, and the Medical Research Council Field Typhus Team, based on the Scrub Typhus Research Laboratory, South East Asia Command. Source: Wellcome Collection.
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![5341 Gater (1930) Appendix 12:9( IV) 17:1(1) Repeds 15 Jan.l5. Page 12. Review of Epidemiology (Audy) apparently reluctant inclusion of man, It is therefore no strange accident that what appears to be the most efficient vector of tsutsugamushi is also one of the relatively few species of mite which happens to attack man. i. question of critical importance is clearly the ability or otherwise of.the vectors to pick up infection from a host such as 2 Rete ye oe If this is possible, as is very likely, then attention should shift from the species which bite man to whatever locally numerous species exist capable of transmitting infection to, and picking it up from the hosts; for the intensity of infection | amongst the man=biting species will be rolated to the intensity of the enzootic. As suggested in Appendix 3, it may readily be et] Te eee Bae eet alis pobgiee™: are of equal or even Pater than is TY ete for the abbas 6Xists in on relatively small numbers that it might be unable to encourage sufficient infection amongst the hosts to maintain an appreciable boosting of newly-acquired infections amongst the mites. A similar situation might obtain in Kuala Lumpur (Lewthwaite, 1930), where T, deliensis is more common on rats but bites man less frecly than does T. akamushi. In any case, for a mite to pick up infection from a host cannot be a very common event, or the meeescae tele would be aan ubiquitous. . In an effort to investigate this problem, Major Kalra first studied the course of infection in the common wild rat of the Imphal arca (Rattus rattus brunneusculus Hodgson), and later attempted to infect T. deliensis experimentally. He found that tis rats suffercd in no way after experimental infection with te tsutsugamushi by the intraperitoneal route. Rickettsiae orth hewever be recovered from the blood within 24 hours, and was possible after at varying intervals up to 99 days. Rickettsiae: reappeared in the blood for several weeks after reinfe¢tion six months later. As suggested by the writer in an earlier report, if the rat: ‘can act as a reservoir it probably does so only temporarily. Kalra's findings are of considerable interest in this connexion. AE led al Seronoriieetcn inom Serene a PAE A UPA FART AN0) Ae Two strains of Re tsutsugatmshi were recovered, but none from controls. ‘The controls were frou oa Mls trapped on the spot, but as the only proper way to control this experinent is to work with laboratory=bred mites, the tie ahi result is suggestive but inconclusive ; Nevertheless, the experinent showed that after 2) hours of feeding.on a heavily cent of the larvae could possibly have picked up infection, if indeed they did this at all. The lower the proportion of mites which actually pick up infection, the more inportant becomes the turnover, in numbers in unit time, of larvac of various species “which can transmit infectiow between the mts. It is worth noting that if we assume that 1 per cent of mites become infected by feeding on a rat with free rickettsiae in its blood, and that, the rickettsaemic phase lasts some 70 days (see Appendix 12, page 9), then an average rat infected at the vory beginning of the Te deliensis peak period in a highly infested area (e.g. Kanglatongbi near Imphal) night possibly infect as many as 15 mites during the rickettstenic phase. This figure is purely hypothetical but is quoted to give a rough scale to such events. '](https://iiif.wellcomecollection.org/image/b32177550_0001_0061.jp2/full/800%2C/0/default.jpg)
