Hospital-Based Surveillance of Rickettsial Diseases in Kashmir, North India

Background: Rickettsial diseases were reported from Kashmir, India, in the early 20th century. Since then, limited research was carried that has resulted in a significant gap in understanding these diseases. This study was conducted to find out the prevalence and diversity of rickettsial diseases in this region. Methods: Blood sample from 476 patients were collected. Enzyme-linked immunosorbent assay was done for the detection of IgM and IgG, and immunofluorescence assay was done for endpoint titer determination. Nested polymerase chain reaction was performed for detection of spotted fever group (gltA, sca0, sca5 genes), typhus group (17 kDa gene) scrub typhus group (47 and 56 kDa gene), followed by sequencing and phylogenetic analysis. Results: The seropositivity of scrub typhus, spotted fever group, typhus group was 74 (15.54%), 71 (14.91%), and 60 (12.60%), respectively. Scrub typhus was significantly associated with the urban population (odds ratio = 1.812, 95% confidence interval 1.099-3.0, p = 0.02). Bimodal seasonal variation was observed in all the three groups. In spotted fever group, out of 48 samples 81.25%, 45.83%, and 38.09% were positive for gltA, sca0, and sca5 genes, respectively, and in typhus group 20.83% were positive for 17 kDa. In the scrub typhus group, out of 62 samples, the 56 kDa gene was positive in 56.45%, while the 47 kDa gene was positive in 35.48%. Phylogenetic analysis revealed Rickettsia conorii, Rickettsia parkeri, Rickettsia typhi, and Orientia tsutsugamushi. Conclusions: This study confirms the presence of human rickettsial infections in Kashmir, highlighting the need for including rickettsial diseases in diagnostic algorithm for acute febrile illness.