Where’s the Eschar?: Non-Eschar Cases and Eschar Distribution between the Serotypes of Karp, Irie/Kawasaki and Hirano/Kuroki Causing Scrub Typhus in Fukushima, Japan

BACKGROUND: Scrub typhus (ST) is endemic in Fukushima, where the highest number has been reported from 2006 to 2011 in Japan. Lack of the triad (fever, rash and eschar) in the clinical features of ST makes the diagnosis difficult especially without eschar. Although genitalia or axillae must be examined carefully as overlooked part of physical examination, the distributions of eschars in the serotypes of ST remain unclear. METHODS: We reviewed the clinical features of the patients diagnosed as ST in adults from 2008 to 2016 at Ohta Nishinouchi General Hospital, a major teaching hospital in Fukushima, Japan. RESULTS: Total 51 cases (serotype Karp 24, Irie/Kawasaki 19, Hirano/Kuroki 8) of ST were confirmed by elevated specific IgM and IgG in the paired sera and the positivity by real-time PCR analysis of eschars. Non-eschar cases were found in 5/51 (9.8%): one of Karp, one of Irie/Kawasaki and three of Hirano/Kuroki. Two eschars were found in a case of Irie/Kawasaki. Total 47 eschars were found in the diagnosed cases. In terms of sex differences, eschars from abdomen to thighs including genitalia were found 4/17 (24%) in men and 17/30 (57%) in women, which is more than twice as high than men. In contrast, eschars in lower extremities from calves to feet were found 5/17(29%) in men and 1/30 (3%) in women. There was no eschar in genitalia and hips in men. In terms of serological type differences, eschars of Karp were found in all of parts of bodies (head, neck, upper extremities, chest, back, abdomen, genitalia, hips, knees/popliteal fossae, and feet). In contrast, no eschar was found in genitalia and hips in Irie/Kawasaki and Hirano/Kuroki. No eschar was found in head, neck and feet in Hirano/Kuroki as well. The contact body sites by vectors, behavior pattern of the patients (passage in women, etc.) and preference to human, such as slow-biter with migration to genitalia or axillae as Leptotrombidium pallidum (L. pallidum; vector of Karp) or quick-biter as L. scutellare (vector of Irie/Kawasaki and Hirano/Kuroki) would be the causes of eschar distribution. CONCLUSION: Eschar is the key feature of ST, so we should not be missed the finding with the high index of suspicion in regards to eschar distribution of the sexes and the serotypes. Atypical presentation such as eschar negative ST should be concerned in this endemic area. DISCLOSURES: All authors: No reported disclosures.