The metamorphosis of Filaria sanguinis hominis in the mosquito / By Patrick Manson.

  • Manson, Patrick, Sir, 1844-1922.
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: The metamorphosis of Filaria sanguinis hominis in the mosquito / By Patrick Manson. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    mosquito, when feeding on the blood of a filarious subject, imbibes the Filaria. Lewis confirms me in the statement that nematodes at a stage of development slightly more advanced than those found in the newly ingested blood are also to be found in the mosquito. But Lewis says he could not satisfy himself that these two forms belong to one and the same species of nematode. Neither he nor Sonsino has found advanced forms, so advanced that from their appearance they would be justified in concluding they were fit for independent life. Possibly, suggests Lewis, the more advanced forms are embryos of some other species of nematode, and not the Filaria sanguinis hominis at all. In my observations I paid particular attention to this point. If I succeed in connecting the more advanced forms of nematode embryo, as seen by Lewis, with the unquestioned embryo Filaria sanguinis hominis found in newly ingested blood, and with the later forms which I had already described as being equipped for independent life, then there is no longer any room for doubt about the r61e of the mosquito, and I can claim that Lewis's observations confirm my own. I would remind the reader that the parasite called Filaria sanguinis hominis is a minute nematode embryo which in certain warm countries is found in the blood of Man. It is the offspring of a mature Filaria living in the lymphatic vessels. The young find their way into the blood-circulation along with the lymph. No form intermediate between the mature Filaria and its embryo has hitherto been found in Man. There is no evidence of growth about the embryo, neither has any provision in its structure by which one might suppose it could pass from one man to another been discovered. It seems most probable, therefore, that like many other parasites it requires the services of an intermediary host—1st, to remove it from the body of the host; 2nd, to nurse it till it becomes equipped for independent life ; 3rd, to place it in a position for obtaining access to its final host. In our search for this intermediary host we must be sure the animal we encounter can fulfil these conditions. In addition to this there are two other circumstances in connex- ion with the Filaria which must also be recognized in fitting it with an intermediary host. Such an animal must have a geographical distribution corresponding to that of the Filaria ; and it must also be nocturnal in its habits. The reason for the first of these conditions is self-evident; the latter is indicated by the curious fact in the history of the Filaria, that the embryo appears in the blood only at night. This peculiarity in the habits of the Filaria has now been so frequently demonstrated and confirmed that I need concern myself here only with the mention of it. There are many reasons why one should regard the mosquito as the animal most likely to fulfil all the conditions required. These reasons I will not enlarge on. I will confine myself to the description of what actually occurs in the relationship of the mosquito to the Filaria, feeling satisfied that in this is the best proof that the mosquito is the true intermediary host of the Filaria sanguinis hominis. In experimenting with the mosquito there are two points I was careful in attending to ; I employed the proper species of insect, and I took care that its only food was the blood of a filariated man. Those who would repeat my experiments must bear these two points in mind. The plan of procedure I found most convenient was as follows :—I 54,*