Scrub typhus is a zoonotic disease caused by Orientia tsutsugamushi, which is transmitted by chiggers. The patient in bitten by chiggers, eschar formation developed in the wound then the rickettsia may disseminate into visceral organs leading to death. In this study, a total of 12 cases of skin specimens confirmed scrub typhus using 47KD immunohistochemistry stain was collected. Skin histopathology revealed leukocytoclastic vasculitis in ten cases and lymphocytic vasculitis in two cases. PCR positive or IgG / IgM result used to confirm scrub typhus was seen in ten cases.

Three autopsy cases were studied to detect Orientia tsutsugamushi distribution in the tissues of the body. The results showed the rickettsia may disseminate into heart resulting in interstitial myocarditis, lung with interstitial pneumonitis then ARDS developed, meninx with aseptic meningitis, brain with encephalitis, renal tubular cells with acute renal failure; liver, spleen, lymph nodes with hemophagocytic syndrome in one case and gastrointestinal tract involvement in two cases. We also demonstrated iNOS in the alveolar macrophages of lungs of in three cases. Thisfinding revealed the infected rickettsia may induce iNOS, then production of large amount of NO which is toxic substance and leads to death.

Key words: Scrub typhus, Immunohistochemistry, iNOS, Orientia tsutsugamushi.