The Increasing Prevalence of Endemic Typhus in Kuala Lumpur and an Evaluation of a Diagnostic ELISA Dot Test for the Detection of Antibodies to Ricketttsia Typhi

WY Sekhar, S Devi
Correspondence: Dr Shamala Devi, shamala@medicine.med.um.edu.my

ABSTRACT
A seroepidemiology study was done in response to the recent increase of Endemic Typhus cases diagnosed at University Hospital. The serosurvey was based on doctors' request for the Weil Felix (WF) or the Indirect Immunoperoxidase (IIP) test in Pyrexia of Unknown Origin (PUO) patients for the years 1991 to 1997. Over the 7 years, we found that the incidence of Endemic typhus is increasing with gender (male:female = 2:1), age (20-40 years) and race distribution (Indians > Malay > Chinese) that reflects socioeconomic circumstances. A commercially available ELISA dot assay [INDX (E2R3) Dip-S-Ticks], for the detection of antibodies against R. typhi was compared with the indirect immunoperoxidase test (IIP). The ELISA assay was done against 219 IIP tested sera. The Dip-S-Ticks was found to be comparable to the IIP with a sensitivity of 91.7% and specificity of 92.8% at cut-off titres of > 1:80 IIP.

Keywords: Endemic typhus, epidemiology, ELISA, IIP
Singapore Med J 2000; 41(5): 226-231