Rocky Mountain Spotted Fever (RMSF) occurs sporadically and infrequently in Indiana. In the past five years the number of cases have ranged from a low of 1 to a high of 10 with a mean of 6 cases/year. Figure 1 presents the number of cases by year for the past 5 years. Figure 2. presents the case distribution by county of residence for 1999. While RMSF may occur across the state, case distribution has a tendency to regionalize in the very southern portion of the state as seen in Figure 3, a presentation of case residences for the past five years. County of residence may not reflect where the disease exposure occurred. The male:female case ratio for the past 5 years is 1:1.1. The age range for RMSF cases in 1999 was from 4 years to 75 years with the mean age 29.5 years

The disease is caused by Rickettsia rickettsii and is transmitted by ticks. The principle vector is Dermacentor variabilis, which is a common tick in Indiana. The disease is characterized by sudden onset with fever, malaise, deep muscle pain, severe headache, chills and conjunctivitis. In approximately 50% of the cases a maculopapular rash appears on the extremities before spreading to the palms and soles. The rash rapidly spreads to the body. Petechiae and hemorrhage are common. In the absence of specific therapy, mortality may be a high as 25% of the cases. With prompt recognition and antibiotic therapy death is uncommon. Diagnosis is confirmed by serological testing of acute and convalescent specimens. Single specimens may be confirmatory if taken after the first two weeks of illness.

There is not a vaccine available to prevent RMSF; therefore prevention rest solely on avoidance of tick infested areas or personal hygiene efforts. Individuals who enter tick-infested areas for recreation or occupational reasons should wear protective clothing (long sleeves and legs), use repellents such as DEET, and check themselves thoroughly for ticks after leaving the tick habitat.

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