Seroprevalence
The aggregated seroprevalence of IgG for the entire study region throughout the complete study period (2013-2022) was 14% (95% CI 12.8—15.2). The study region seroprevalence of IgM was 10.98% (95% CI 9.8—12.2) for the 3,277 pig samples tested for IgM from 2017—2022. During this same reduced period, the study region IgG seroprevalence was 9.73% (95% CI 8.5—11.0). For each age group during this period, the agreement (Cohen’s kappa , κ) between IgG and IgM tests was 0.60, 0.41, and 0.59 in pigs aged 4-5 months, 6-12 months, and >12 months, respectively.
Sant Kabir Nagar had the highest seroprevalence of IgG (25.4%; 95% CI 20.8—30.4), and Maharajganj had the lowest seroprevalence of IgG (4.4%; 95% CI 2.2—6.9), aggregated throughout the study period (Figure S4). Seroprevalence of IgG did not increase with age across the study region (Figure S5). Furthermore, when the data were stratified by district, no consistent pattern emerged in the point estimates of seroprevalence, with only Azamgarh, Ballia and Kushinagar demonstrating a moderate increase with age. (Figure 2). The lack of consistent increasing seroprevalence with age suggests that IgG antibodies induced following natural infection with JEV are transient, so further analyses of IgG seroprevalence were conducted stratified by pig age to investigate this phenomenon further (Sections 3.3.2-3.3.3), followed by analysis of the entire IgG dataset (all ages: Section 3.3.4).