Possibility of scrub typhus in fever of unknown origin (FUO) cases: An experience from Rajasthan

Purpose: Fever of unknown origin (FUO) has multiple causes. Scrub typhus is less known cause of FUO in India. The present study reports a recent epidemic of scrub typhus amongst cases of FUO from different areas of Rajasthan, India. There was high mortality in undiagnosed cases of FUO which lead to the diagnosis of scrub typhus. Objective: To study the possibility of scrub typhus as a causative factor in FUO cases by qualitative detection of IgM antibodies with ELISA. Materials and Methods: From September 2012 to December 2012, 271 serum samples of FUO cases were analysed for IgM antibodies to Orientia tsutsugamushi along with dengue, malaria, typhoid, tuberculosis and brucellosis. Results: Scrub typhus IgM antibodies by ELISA were detected in 133 (49.1%) patients. Scrub typhus positivity was significantly higher among female in comparison to males (P < 0.05). Maximum positivity of scrub typhus was found in females of 46-60 years age group. The laboratory parameters were abnormal in most of the patients as evident by thrombocytopenia (63%), deranged liver functions (56%) and renal functions (25%). Conclusion: The present study emphasises the importance of scrub typhus among cases of FUO especially after rainy season and during early cooler months. The study also highlights the significance of ELISA method for rapid and early reporting and ruling out scrub typhus in FUO cases.