. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. ROCKY MOUNTAIN SPOTTED FEVER 189 Spotted Fever Group In the Rocky Mountain districts of northwestern United States there exists a disease commonly known as Rocky Mountain spotted fever. In certain parts of Japan and in some of the East Indian Islands and Malay States there occurs a very similar disease known as kedani or flood fever, in Sumatra called pseudo- typhus. These diseases, widely separated as they are, have a remarkable number of points in common. Both are caused by parasites, presumably proto
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. ROCKY MOUNTAIN SPOTTED FEVER 189 Spotted Fever Group In the Rocky Mountain districts of northwestern United States there exists a disease commonly known as Rocky Mountain spotted fever. In certain parts of Japan and in some of the East Indian Islands and Malay States there occurs a very similar disease known as kedani or flood fever, in Sumatra called pseudo- typhus. These diseases, widely separated as they are, have a remarkable number of points in common. Both are caused by parasites, presumably protozoans, which have not yet been dis- covered; both are transmitted by members of the order Acarina, spotted fever by ticks and kedani by mites, though it is believed that the Sumatra type of kedani may be transmitted by ticks also. Both diseases have a short incubation period, and both follow a very similar course — a skin eruption, con- tinued high fever, and fre- quently high fatality. It is quite probable that these two diseases will be found to be caused by closely related para- sites. Their occurrence in such widely separated localities as northwestern United States and eastern Asia is an inter- esting fact. Rocky Mountain Spotted Fever. — For many years certain limited districts in the Rocky Mountain region of northwestern United States (Fig. 58), particularly Idaho and Montana, have been known to be affected by this very serious disease. Its yearly occurrence in well-defined areas has given rise to panic and hysterical fear of entering the " haunted " places. Houses were deserted, land depreciated in value, and some of the richest valleys in the Northwest left unpopulated. In 1906 it was shown by Ricketts that the disease was invariably preceded by the bite of a common local wood-tick, Dermacentor venustus (see p. 361, and Fig. 156), which was experimentally shown to be the intermediate host of the Fig. 58. Map showing distribution of Rocky Mounta
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