Important Clinical Features of Japanese Spotted Fever

Japanese spotted fever (JSF) is a zoonosis transmitted by ticks carrying the pathogen Rickettsia japonica. The classic triad of JSF symptoms is high fever, erythema, and tick bite eschar. About 200 people in Japan develop the disease every year. Japanese spotted fever is also a potentially fatal disease. At Minami-Ise Municipal Hospital in Japan, 55 patients were diagnosed with JSF from 2007 to 2015, which was equivalent to 4.3% of the total JSF cases in Japan. In this retrospective study, we examined the medical records of these 55 JSF cases. Fever, erythema, eschar, and elevated C-reactive protein (CRP) are characteristic clinical features of the disease. We confirmed four of these in the reviewed cases; however, eschar was not present in occasional cases. We confirmed that eosinopenia appeared in nearly all cases. Using fever, erythema, elevated CRP, and eosinopenia in diagnostic screening, our positivity rate was 90.9%. In our clinical practice, including eosinopenia improves the initial diagnosis of JSF.