In 1964, 135 male and 223 female Dermacentor andersoni Stiles were collected at 48 national forest recreation areas in Utah. Using guinea pigs immunological tests were performed on each of 62 samples to determine the presence of the Rocky Mountain spotted fever rickettsia. Thirteen of the samples (21 percent) were positive. These 13 samples contained 35 males and 34 females yielding an infection rate of at least 3.6 percent, assuming one infected tick was in each sample.
Herrin, C. Selby
"Incidence of spotted fever in wood ticks of Utah recreational sites,"
Great Basin Naturalist: Vol. 33
, Article 3.
Available at: http://scholarsarchive.byu.edu/gbn/vol33/iss1/3