. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 42 SPIROCHETES includes such diseases as syphQis, yaws, and infectious jaundice. The third type is that in which occur only local ulcerating sores of skin or mucous membrane; of such a nature are the other diseases named above. Relapsing Fever In every continent in the world, with the possible exception of Australia, there occurs a form of relapsing fever caused by spiro- chsetes in the blood. In Africa it ranks next to malaria and sleeping sickness as a scourge of that disease-cursed country. In India
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 42 SPIROCHETES includes such diseases as syphQis, yaws, and infectious jaundice. The third type is that in which occur only local ulcerating sores of skin or mucous membrane; of such a nature are the other diseases named above. Relapsing Fever In every continent in the world, with the possible exception of Australia, there occurs a form of relapsing fever caused by spiro- chsetes in the blood. In Africa it ranks next to malaria and sleeping sickness as a scourge of that disease-cursed country. In India it is hardly less severe, while in Eastern Europe and America it is a mild disease. The clinical effects of these various strains of the disease vary, especially in the number and duration of the relapses. The mode of transmission also varies and the parasites are apparently distinguishable and are therefore given different scientific names. The African spirochsete, Spirochceta duttoni (Fig. 6), is the largest, being about 16 ^ (tsVjt of an inch) in length; it has only two or three complete spiral turns and is quite generally admitted to constitute a distinct species. The other forms, Sp. recurrentis of Europe, Sp. novyi (Fig. 5B) of America, Sp. carteri of ori- ental countries, and perhaps still others in other regions, are often looked upon as mere strains or varieties of Sp. re- FiG. 6. SpirochiBta duttoni in blood of currentis, which was the one experimentally infected rat. Upper indi- gj.^^ described. These SO- vidual shows transverse fission. X 1000. ,, , . _.„ (After Novy and Knapp.) called species differ among themselves chiefly in size, and in the closeness and regularity of the coils. Each type, however, is quite variable within itself, and one is likely to be misled as to size by the hanging together of several individual or partially divided spirochaetes in a chain. The varying symptoms of the different types of the disease and the fact that immunity to one does n
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