CHAPTER XXXVIII
SPOTTED FEVER OF THE ROCKY MOUNTAINS
Definition and Synonyms
Definition.—The disease is chiefly reported from certain sections of the states of Montana and Idaho. The virus is not filterable and is probably bacterial in nature and is transmitted solely by the tick, Dermacentor andersoni, which arthropod host gets its infection from certain rodents of the section serving as virus reservoirs.
Maxey described the disease as follows: “An acute endemic, noncontagious, but probably infectious febrile disease, characterized clinically by a continuous moderately high fever, severe arthritic and muscular pains and a profuse, petechial eruption in the skin, appearing first on the ankles, wrists and forehead but rapidly spreading to all parts of the body.”
Synonyms.—Rocky Mountain fever. Tick fever of the Rocky Mountains. Black fever. Blue disease.
History and Geographical Distribution
History.—The disease was first noted in the Snake River Valley of Idaho, about 1893, and in the Bitter Root Valley of Montana, about 1890. There is some evidence that the disease may have existed among the Indians prior to the advent of white settlers in the Bitter Root Valley. The disease was first described by Doctor M. W. Wood, U. S. A., in 1896. It is interesting to note that the first white settlers of the Bitter Root Valley suffered from what was considered a very fatal form of “black measles.”
In 1902 Wilson and Chowning reported that the disease was due to a piroplasm of the squirrel and that it was transmitted to man by the bite of a tick (Dermacentor venustus). Later Ashburn and others, while accepting the tick transmission, failed to corroborate the piroplasm etiology.
It is chiefly to Ricketts that we owe much of our detailed knowledge of the epidemiology of the disease.
The work of McClintic and Frick along lines of prophylaxis has given us practical measures for the control of the disease.