Clinical and Sero Immunological Profile of Scrub Typhus in Bengaluru, Southern India

Abstract

Introduction: Scrub typhus is a common but neglected cause of Acute Febrile Illness (AFI) in India. Under diagnosis of this severe disease with protean manifestations, can negatively influence the treatment and outcome. Early laboratory diagnosis by appropriate means is therefore important. In addition, as antigenically diverse variants of Orientia tsutsugamushi (O.tsutsugamushi)are known to exist and evolve, information regarding the strain types is also crucial. Aim: To know the clinical spectrum, laboratory diagnosis by different modalities, outcome and strain variation of scrub typhus in Southern India. Materials and Methods: A prospective cross-sectional study was conducted in a Tertiary Care Hospital in Bengaluru, Southern India from June 2015 to May 2017. Hundred clinically suspected cases of scrub typhus (rickettsioses) were enrolled. Serum and EDTA (Ethylenediaminetetraacetic acid) blood samples were subjected to serodiagnosis for scrub typhus and Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) respectively. Strain characterisation was done by Microimmunofluorescence (MIF), PCR-RFLP and phylogenetic analysis. Patients were followed-up for four weeks. Data was entered in Microsoft Excel spreadsheet and analysed using Statistical Package for the Social Sciences (SPSS) software. Results: Laboratory evidence of scrub typhus was showed by 38% of the cases. Seropositivity was more in comparison to PCR. Paediatric preponderance and seasonal trend was evident. Strain typing showed presence of different strain types, with no correlation between clinical features and strain types. PCR-RFLP results correlated well with phylogeny, while MIF results did not match. All the patients responded to doxycycline, except for 12% who succumbed. Conclusion: Different strain types of O. tsutsugamushi are known to cause scrub typhus in Southern India. PCR-RFLP can be a useful preliminary tool for strain typing in resource poor settings, where phylogenetic analysis is not possible. Early diagnosis and treatment helps in improved outcome.