Lyme Disease 2004
*Rate per 100,000 population based on the U.S. Census Bureau’s population data as of July 1, 2004
Lyme disease is caused by the bacterium Borrelia burgdorferi and is the most commonly diagnosed tick-borne disease in Indiana. It is transmitted by the deer tick (Ixodes scapularis) by using small wild rodents as its reservoir. Transmission can occur after the tick has been attached and feeding for approximately 36 hours. Signs and symptoms can appear 3 to 30 days postexposure but generally occur 7 to 14 days postexposure.
In 2004, 32 cases of Lyme disease were reported in Indiana, for a rate of less than 1 case per 100,000 population (Table 1). Figure 1 shows the number of reported cases per year for 2000-2004. Incidence of disease was greatest during the summer months (Figure 2). Over 70 percent of reported cases occur from May through September when ticks are active. As shown in Figure 3, age-specific rates were highest among adults aged 60-69 years (0.83), followed by adults aged 40-49 years (0.74). Lyme disease cases were reported more in the northwestern part of the state. Nineteen counties reported Lyme disease cases; however, no county reported five or more cases.