Development and evaluation of a latex agglutination test for the rapid diagnosis of scrub typhus.

The purpose of this research was to develop a simple and rapid diagnostic test for scrub typhus using a latex agglutination test (LAT) to detect antibodies against Orientia tsutsugamushi. Five strains of O. tsutsugamushi were propagated in L929 cells. The rickettsiae were purified and concentrated with percoll density gradient centrifugation. A suitable concentration of O. tsutsugamushi soluble antigen was used to sensitize latex to prepare the latex antigen. The specificity, sensitivity, and accuracy of the latex antigen were assessed. The LAT, indirect immunofluorescent antibody test (IFA), and Weil-Felix agglutination test (WF) were compared by testing 109 acute febrile illness cases and 100 confirmed non-scrub typhus cases (50 other febrile disease cases and 50 healthy controls). By using the IFA as the standard reference method, the overall sensitivity, specificity, and accuracy of the LAT were 89.1, 98.2, and 93.6%, respectively. By contrast, the sensitivity of the WF, compared with the IFA, was only 47.3%, while the specificity and accuracy were 92.6 and 69.7%, respectively. Thus, the LAT described here is another important alternative test for the diagnosis of scrub typhus.

Septic shock secondary to scrub typhus: characteristics and complications.

Scrub typhus is an acute febrile illness caused by infection with Orientia tsutsugamushi transmitted by the bite of larval trombiculid mites (chiggers). A prospective study was conducted in septic shock patients in Maharat Hospital, Nakhon Ratchasima Province, Thailand, from 12 November 2001 to 5 January 2002. Of the 51 septic shock patients studied during the 7 week period, 18 (35.3%) were found to have evidence of scrub typhus infection; 3 patients (16.7%) died. In this study, septic shock caused by Orientia tsutsugamushi is the most prominent (35.3%) in endemic area of scrub typhus. Scrub typhus with septic shock patients results in organ failure: respiratory failure, DIC were predominant, followed by renal and hepatic involvement. Two deaths were due to respiratory failure and one death was as a result of combined respiratory and renal failure. Fever was the most common symptom, followed by headache, myalgia and dyspnea; lymphadenophathy and eschar are common signs. Laboratory findings revealed that almost all of the patients had a mild leukocytosis, reduced hematocrit and thrombocytopenia; SGOT, ALP, direct bilirubin (DB), total billirubin (TB), BUN, Cr were elevated; hypoalbuminemia was noted. Urinalysis showed that 88.9% of the patients had albuminuria. 77.8% of patients had abnormal chest X-rays.