"Is it time to initiate scrub typhus surveillance in Karnataka?"-Lessons from a seroprevalence survey in a rural district

Background:Scrub typhus, caused by Orientia tsutsugamushi, is a commonly occurring, but underdiagnosed rickettsial infection in India. Considering the high incidence of scrub typhus among patients with acute febrile illness in the hospital setting and the paucity of community seroprevalence studies, we aimed to estimate the prevalence of scrub typhus in the community in the Bengaluru Rural District.Methods:A pilot cross-sectional survey was conducted between October and December 2022 among eligible asymptomatic adults from five randomly selected villages of the Bangalore Rural District after obtaining written informed consent. Serum immunoglobin M (IgM) and immunoglobin G (IgG) antibodies were tested using the respective enzyme-linked immunosorbent assay (ELISA) kits from InBios International Inc, Seattle, USA. Seroprevalence was defined as positivity to either IgG or IgM antibodies or both.Results:The study reported a seroprevalence of 8.9% (95% CI 4.8%-14.7%) among 146 asymptomatic adults. The IgG and IgM antibodies were positive in 7.5% and 2.1% of participants, respectively.Conclusions:A community seroprevalence of 8.9% warrants further epidemiological surveys and surveillance in the context of climate change, variable clinical presentations of scrub typhus, and the possible need to include this disease in the clinical practice algorithm in the primary care setting. We recommend study designs with "One Health" lens to monitor the trend of this re-emerging public health problem.