Contributor: Gordon K. Klintworth
Scrub typhus (Kedani fever, chigger-borne typhus, akamushi fever, flood fever, tsutsugamushi disease, Japanese river fever, Shishito fever, mite typhus, rural typhus) is a rickettsial infection caused by Orientia tsutsugamushi that is endemic in Japan, southern and eastern Asia, Northern Australia and islands of the western and Southwestern Pacific Ocean. Rodents are the reservoir for the infection, which is spread by chiggers belonging to the genus Trambicula (Trambicula akamushi in Japan and Trambicula deliensis outside of Japan). Frequently a focal area of  necrosis occurs in the dermis and epidermis at the site of inoculation and this may involve the eyelid forming an eschar or tache noire. Following an incubation period the pathogenic rickettsia infect the vascular endothelium of blood vessels  in many parts of the body. The initial symptoms include fever, a severe headache, nausea, vomiting and myalgia. The cardinal lesions of the vascular endothelium result in edema and hypovolemia. The edema accumulates in the soft tissues of the skin, but may also involve the lung [edema - lung]. Prior to antibiotics the mortality was >20%, but early treatment with tetracycline or chloramphenicol has decreased this substantially.