Prevalence of Scrub typhus among Patients attending a Tertiary Care Hospital - A Prospective and Retrospective study

Abstract

Background: Scrub typhus is an emerging acute febrile illness caused by a gram-negative obligate intracellular bacterium, Orientia tsutsugamushi. It is transmitted by a chigger mite that acts as a vector. This study was carried out to understand the prevalence, clinico-haematological profile and clinical outcome of patients who tested positive for scrub typhus (ST). Materials and Methods:This study, both retrospective and prospective, was conducted in the Department of Microbiology, Chettinad Hospital and Research Institute, a tertiary care teaching hospital located in the suburbs of Chennai. The study period was from October 2019 to December 2022. Blood samples from clinically suspected scrub typhus patients were tested by the immunochromatographic test, a rapid card that detects both IgG and IgM antibodies for scrub typhus. The demographic, clinico-haematological parameters and disease outcome of the patients who tested positive for scrub typhus were analysed.Results: 1021 patients who presented to the hospital with febrile illness and clinical suspicion of scrub typhus were tested for this disease. Of these patients, 93 were IgM-positive. Common haematological abnormalities observed were leucocytosis, thrombocytopenia, anaemia, lymphocytosis, and monocytosis, along with elevated c-reactive protein, hypoalbuminemia, raised transaminases and an increase in serum creatinine. Dengue co-infection was diagnosed in 5% of the patients and leptospirosis in 1% of the patients. Conclusion:The serological prevalence of scrub typhus was found to be 9.1% and it should be regarded as an important aetiological agent in patients presenting with fever. As an eschar may not be detected in all patients, the diagnosis relies profoundly on prompt laboratory investigations which can aid in swift diagnosis and rapid initiation of therapy.