World Distribution of Spirochetal Diseases

2. Relapsing Fevers Louse-borne and Tick-borne. American Geographical Society, Plate 16, Atlas of Diseases. New York, American Geographical Society. 1955. Price $1.25 folded; $1.50 flat

Gordon E. Davis
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The relapsing fevers are divided, as usual, into louse-borne and tick-borne types. It is well stated that the epidemiology of the louse-borne type is similar to that of the louse-borne form of typhus. It is correctly stated that transmission by the louse is not by bite but through the medium of the crushed louse. In comparing the two types, it is stated that the tick-borne type is “more endemic in nature.” It is endemic, never epidemic. The statements that “infection occurs most often by the penetration of the spirochete through an abrasion of the skin” and that “transmission can also occur by bite” are misleading. For the most part, infection takes place through the medium of the secretions of the salivary glands while the tick is feeding. The general statement that: “One factor dominates the epidemiology—the transovarial transmission of the spirochete through several generations of ticks” is unwarranted. In 0. turicata, transovarial transmission (up to 100 per cent) has been shown.

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