Seroprevalence of spotted fever group rickettsiosis in Kashmir: A community-based study using indirect immunofluorescence assay

Rickettsial infections, caused by obligate intracellular Gram-negative bacteria, are an emerging public health concern globally, particularly in regions like India, where the epidemiology remains largely underexplored. The study aimed to determine the seroprevalence of spotted fever rickettsiosis (SFR) in the Kashmir Valley, using the indirect immunofluorescence assay (IFA), the gold standard for rickettsial diagnosis.

This prospective, population-based study was conducted over three years at the Sher-i-Kashmir Institute of Medical Sciences, Srinagar. A multistage random sampling technique was used and a total of 571 individuals across 10 districts were included in the study. Blood samples were analysed for SFR IgG antibodies using IFA. Data was collected through a house-to-house survey, including demographic and environmental risk factors. Statistical analysis was performed using SPSS version 23, with significance set at P < 0.05.

Of the 571 participants, 143 (25 %) tested positive by IgG immunofluorescence assay for SFR. The majority of seropositive cases were males, 52.4 % (n = 75). Seropositivity was highest in the >50 year age group and among participants having risk factors like contact with uncut vegetations, collection of Firewood And living near Forests. The seroprevalence varied significantly across districts, with the highest prevalence observed in Pulwama. Risk factors associated with higher seropositivity included contact with shrubs, milking and animal slaughtering. No significant associations were found between gender, urban/rural residence, or age group and seropositivity.

This study highlights a high seroprevalence of spotted fever in the Kashmir Valley, emphasizing the significant public health burden in the region. Early detection and targeted prevention strategies, particularly in high-risk areas, are crucial for effective control and management of spotted fever in this region.