Since the evidence all indicates that Rocky Mountain spotted fever is transmitted solely by the tick, and that some of the wild animals serve as reservoirs of the virus, it is obvious that personal prophylaxis consists in avoiding the ticks as fully as possible, and in quickly removing those which do attack. General measures along the line of tick eradication must be carried out if the disease is to be controlled. That such measures are feasible has been shown by the work which has been done in controlling the tick-borne Texas fever of cattle, and by such work as has already been done against the spotted fever tick, which occurs on both wild and domestic animals. Detailed consideration of these measures is to be found in the publications of the Public Health and Marine Hospital Service, and the Bureau of Entomology. Hunter and Bishopp give the following summarized recommendations for control or eradication measures in the Bitter Root Valley. (1) A campaign of education, whereby all the residents of the valley will be made thoroughly familiar with the feasibility of the plan of eradication, and with what it will mean in the development of the valley. (2) The obtaining of legislation to make it possible to dip or oil all live stock in the Bitter Root Valley. (3) The obtaining of an accurate census of the horses, cattle, sheep, mules, and dogs in the valley. (4) The construction of ten or more dipping vats. (5) The providing of materials to be used in the dipping mixture. (6) The organization of a corps of workers to carry on the operations. (7) The systematic dipping of the horses, cattle, sheep, and dogs of the valley on a definite weekly schedule from approximately March 10 to June 9. (8) The treatment by hand of the animals in localities remote from vats, on the same schedule. They estimate that after three seasons' operations a very small annual expenditure would provide against reinfestation of the valley by the incoming of cattle from other places. Supplementary measures consist in the killing of wild mammals which may harbor the tick; systematic burning of the brush and debris on the mountain side; and in clearing, since the tick is seldom found on land under cultivation. CHAPTER X ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA [_Continued_] ARTHROPODS AND SPIROCHÆTOSES OF MAN AND ANIMALS The term spirochætoses is applied to diseases of man or animals which are due to protistan parasites belonging to the group of slender, spiral organisms known as spirochætes.