The distribution and dynamics of Rickettsia in the tick population of Ohio.

A five-year survey of ticks and associated rickettsia in Ohio shows a partitioning of spotted fever group rickettsia (namely, Rickettsia montana and R. rickettsii) into three areas of the state where the majority of human spotted fever cases occur. The percentage of ticks infected, even in areas with a high incidence of disease, is remarkably low, less than 1%. The statewide infection rate for R. bellii approaches 3%, and this organism appears to be more evenly distributed throughout the state. Dermacentor variabilis, which accounts for 97% of Ohio ticks received for testing, is the only species which has been found to harbor rickettsia. Ohio's tick testing program is not an effective surveillance tool and is of no use in diagnosing tick-borne disease. However, the program does function as an excellent means of increasing public awareness of tick-borne disease.