Serological Evidence of Scrub Typhus among Cases of PUO in the Kashmir Valley-A Hospital Based Study

Introduction: Rickettsial infections are being increasingly recognized as a cause of acute febrile illnesses and should be considered a distinct possibility in patients presenting with suggestive clinical features. Their diagnosis remains a challenge in a country like ours where tests like immunofluorescence assay cannot be routinely done. Results of serological tests, when correlated with patients clinical profile can aid in the timely diagnosis of scrub typhus. Aim: To find out the extent to which scrub typhus contributes to Pyrexia of Unknown Origin (PUO) in patients admitted to or attending the OPD of our hospital using simple tests like Weil-Felix Agglutination Test (WFT) and Enzyme Linked Immunosorbent Assay (ELISA). Materials and Methods: A cross-sectional study was carried out in the Department of Microbiology, Government Medical College and Hospital, Srinagar, over a period of eight months (1st March to 31st October 2015). Serum samples from patients suffering from Pyrexia of Unknown Origin (PUO) were processed for the detection of Scrub typhus. A total of 162 samples were included in the study. These were subjected to WFT using OX-K strain. The serum samples were diluted 1/20 to 1/640 and a titre of >= 1:160 was considered as positive. The samples were also tested for IgM and IgG antibodies for scrub typhus by ELISA and tube agglutination test was done to detect typhoid fever and brucellosis. Results: Of the 162 serum samples tested 22.8% tested positive scrub typhus by WFT. IgM ELISA and IgG was positive in 8 (4.9%) and 15 (9.3%) samples respectively. Sensitivity, specificity, positive and negative predictive values of WFT; taking IgM ELISA as a reference standard were 75%, 79.9%, 16.2% and 98.4% respectively. Conclusion: Scrub typhus is prevalent in our state and the results of WFT supplemented by those of ELISA can aid in its diagnosis. However the results of these tests should always be regarded in light of the clinical condition of the patient.