Brigham Young University Science Bulletin, Biological Series


Arthropoda, Rocky Mountain spotted fever, Plague


Through the courtesy of the National Institutes of Health, Grants and Fellowships Division, a project was established at Brigham Young University to study the distribution and host relationships of vectors for Rocky Mountain spotted fever and plague in the state of Utah.

Rocky Mountain Spotted Fever
Of the four capable vectors listed as present in the United States, Dermacentor andersoni and Haemaphysalis leporis palustris are found in Utah. Listed for Utah as potential (experimental) vectors are Dermacentor parumapertus, Dermacentor albipictus, Rhipicephalis sanguineus and Ornithodoros parkeri. Of the potential vectors D. parumapertus is the only species having extensive distribution in Utah.

1. Plague as a disease in Utah does exist. It has been known to be present since 1936 and since that time the disease has been identified in thirteen of the twenty-nine counties of the state.

2. Of the sixty-eight species and subspecies of plague-implicated mammals in the western United States, forty-one species and subspecies are represented in Utah. There is not a single county without one or more plague-implicated mammal species being present and widely distributed, and from which plague-implicated vectors have been taken.

3. As a result of these studies it has been found that there are thirty-one species and subspecies of fleas occurring in Utah as plague-implicated vectors. They are classified as being capable (natural) and potential (experimental) vectors. Twenty species are listed as capable and eleven as potential vectors.

4. Both capable and potential vectors have wide geographic distribution and variable host adaptations. For example, Diamanus montanus, a very efficient vector for plague, occurs on twenty genera other than the genus Citellus in Utah. It is commonly listed as a squirrel flea, but it is found on at least eighteen species of mammals other than members of the squirrel genus as far as Utah is concerned.

5. Every Utah county has one or more capable plague-implicated vectors present. Efficient plague-implicated vectors of several species, and plague-implicated hosts, are found to be densely distributed where human populations are most highly concentrated in the state.