1342 SPOTTED FEVER OF THE ROCKY MOUNTAINS 



( = D. andersom = D. vemistus Banks nec Marx). In 1903 Anderson 

 was instructed to investigate the disease, and as a result of his 

 inquiries he supported Wilson and Chowning as regards both the 

 parasite and the tick. In 1905 Stiles published his zoological 

 investigation into the cause, transmission, and source of Rocky 

 Mountain spotted fever, in which he failed to find evidence of the 

 existence of the parasite in man or squirrel, and of the transmission 

 by the tick. His researches were supported in the same year by 

 Ashburn. In 1906 King found distinct experimental evidence of 

 the transmission of the disease by the tick. From 1906 until his~ 

 recent death Ricketts has been working at the aetiology of the 

 malady, and has proved that the tick D. andersoni spreads the 

 disease — a conclusion which he has supported by experiments on 

 guinea-pigs and monkeys; but he says that the credit for proving 

 the transmission of the disease from man to man by the tick must 

 be given to McCalla and Brereton. In 1908 Ashburn and Craig 

 published an excellent paper on this and the tsutsugamushi disease, 

 which they indicate to be distinct from one another, and in this 

 paper Ashburn accepts the transmission by the tick. Ricketts 

 in 1909 found that there were really two different ticks implicated 

 in the spread of the disease, and these were recognized as D. 

 venustus Banks, igoS^D. andersoni Stiles = Z). venustus Marx, 1897, 

 pro parte, and D. modesfus Banks, of which we have been unable 

 to find a description. It is obvious that there is great confusion 

 as to the correct nomenclature of the ticks causing this fever. We 

 follow Stiles, and call the best-known tick D. andersoni. 



Climatology. — ^The disease is only known in the United States, 

 in Washington State, Oregon, Montana, Idaho, Nevada, Wyoming, 

 Utah, and Colorado. It has not been reported from New Mexico, 

 as far as we know, but the causal tick is found there and the fever 

 probably exists therein. In Montana it is found in the Bitter Root 

 Valley, on the eastern slopes of the Bitter Root Mountains, and 

 from there to the western bank of the Bitter Root River, by which 

 it is apparently bounded, the worst area being from Lo-lo to Como, 

 a distance of about fifty miles in length, but only about four to five 

 miles in breadth. This country has a considerable snowfall, which, 

 though it begins to melt in March, lies on the mountains until mid- 

 June. The melted snow drains into the river, which does not reach 

 low-water until July. It is only during this period that the ticks 

 / [D. andersoni) appear in large numbers, and infest men and animals 

 who pass through the forests, thickets, and uncultivated regions. 

 The disease is also known at Rock Creek, 20 miles, and at Bridger, 

 200 miles, east of the Bitter Root River. In Idaho it occurs through- 

 out the entire valley of the Snake River, including its tributaries, 

 and the foot-hills in the neighbourhood. In Wyoming it is found at 

 Cody and Meeteeste. In Nevada it is only known in the north, 

 in the valley of the Quinn River, where it was recognized as far 

 back as 1887. In Oregon it is said to be mild, and to be found 

 only in the eastern portion, towards Idaho. 



