Epidemiology of scrub typhus in a tertiary care hospital of Southern Odisha: a cross sectional study

Purpose: Scrub typhus, is a mite-borne disease caused by bacteria named Orientia tsutsugamushi. In recent years the incidence of scrub typhus is increasing day by day. The disease is easily missed because of low sensitization among clinicians and non-specific clinical manifestation. The disease can be fatal in untreated cases. With the availability of testing methods, it can be easily diagnosed and treated. This study aims to depict the epidemiology of scrub typhus in southern Odisha.Methods: A total of 170 blood samples were collected from clinically suspected acute undifferentiated febrile illness (AUFI) cases. Samples were tested serologically for antibodies against Orientia tsutsugamushi by commercially available Immunochromatography test (ICT) and enzyme-linked immunosorbent assay (ELISA) kit as per the manufacturer's instruction. Molecular diagnosis was done by nested polymerase chain reaction (N-PCR) and Sanger sequencing was done to know the circulating strains.Results: Out of 170 cases of AUFI, 74 cases were diagnosed scrub typhus by IgM ELISA and 67 were positive by ICT. Males were affected more and cases were more clustered in the Ganjam district. The disease followed a typical seasonal i.e. more cases were seen in cooler months of the year. Sequencing revealed the strains were Gilliam and Karp like.Conclusions: The burden of scrub typhus was 43.5% among the study population. Determining the serotypes in endemic areas is important for basic research on the classification of Orientia tsutsugamushi, the development of vaccines, and the definitive diagnosis of scrub typhus. Expanding the panel of antigens used to test scrub typhus and to take into account of local antigenic diversity would improve the sensitivity of serological diagnosis.