Seroprevalence of Scrub Typhus among Pyrexia of Unknown Origin Patients: A Study from Tertiary Care Hospital in Eastern Odisha, India

Introduction: Scrub typhus is a fatal rickettsial infection. It is caused by mite-borne bacterium Orientia tsutsugamushi which is transmitted by the bite of mite larvae called chiggers. It usually presents with acute febrile illness. Clinicians usually do not consider it as differential diagnosis as it is still an unknown entity. Aim: To assess the seroprevalence of scrub typhus among the pyrexia of unknown cases in Eastern part of Odisha, India. Materials and Methods: This was a cross-sectional study involving 260 serum samples obtained from clinically suspected cases of scrub typhus. Detection of antibodies was done on the samples by Immunochromatography (ICT) and IgM ELISA (Enzyme Linked Immunosorbent Assay). Samples were also processed for dengue fever, malaria, typhoid and leptospirosis which are the other causes of febrile illness in this region and excluded from the study once they come positive. Among these febrile cases which were excluded from study, malaria was predominant (44%) followed by typhoid (34.4%), dengue (15%) and leptospirosis (6.45%). Descriptive statistical analysis was applied to evaluate the results. Results: Out of 260 clinical samples, 74 (28.46%) were positive by IgM ELISA. There was good correlation (98.6%) between ICT and IgM ELISA. Fever was the most common clinical symptom followed by abdominal pain. Pathognomonic feature such as eschar was seen in one patient only. Scrub typhus should be considered as one of the differential diagnosis of Pyrexia of Unknown Origin (PUO) cases, along with dengue fever, malaria typhoid and leptospirosis. Conclusion: IgM ELISA is simple, rapid and economical test and should be used as reference diagnostic test for the diagnosis of scrub typhus.