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).