Rocky Mountain Spotted Fever 2003
*Rate per 100,000 population based on the U.S. Census Bureau’s population data as of July 1, 2003
Rocky Mountain spotted fever (RMSF) is caused by the bacteria Rickettsia rickettsii. RMSF is transmitted in Indiana by the dog tick (Dermacentor variabilis), which lives in wooded areas and tall, grassy fields. RMSF occurs 5-10 days after a bite from an infected tick. Signs and symptoms include high fever, severe headache, nausea, vomiting, muscle and joint pain, and lack of appetite, followed by a rash. Early treatment with antibiotics ensures recovery.
During the five-year period 1999-2003, 25 cases of RMSF were reported in Indiana, including 2 cases in 2003 (Figure 1). The disease is most common in the spring and summer months when ticks are active but can occur anytime during the year when the weather is warm (Figure 2). In Southern Indiana, ticks may be active into the late fall. Age-specific rates are usually greatest for young children from 1-9 years of age; however, in 2003, rates were greatest for adults aged 40-59 years of age (Figure 3). RMSF may occur in all areas of Indiana, but most cases occur in the southern portion of the state. Cases are reported by county of residence and may not always reflect where the tick exposure occurred.