Spatio‐temporal epidemiology of Japanese encephalitis virus infection in pig populations of eastern Uttar Pradesh, India, 2013–2022

Abstract

AimsJapanese encephalitis (JE) is endemic in India. Although pigs are considered important hosts and sentinels for JE outbreaks in people, limited information is available on JE virus (JEV) surveillance in pigs.Methods and ResultsWe investigated the spatio‐temporal distribution of JEV seroprevalence and its association with climate variables in 4451 samples from pigs in 10 districts of eastern Uttar Pradesh, India, over 10 years from 2013 to 2022. The mean seroprevalence of IgG (2013–2022) and IgM (2017–2022) was 14% (95% CI 12.8–15.2) and 10.98% (95% CI 9.8–12.2), respectively. Throughout the region, higher seroprevalence from 2013 to 2017 was observed and was highly variable with no predictable spatio‐temporal pattern between districts. Seroprevalence of up to 60.8% in Sant Kabir Nagar in 2016 and 69.5% in Gorakhpur district in 2017 for IgG and IgM was observed, respectively. IgG seroprevalence did not increase with age. Monthly time‐series decomposition of IgG and IgM seroprevalence demonstrated annual cyclicity (3–4 peaks) with seasonality (higher, broader peaks in the summer and monsoon periods). However, most variance was due to the overall trend and the random components of the time series. Autoregressive time‐series modelling of pigs sampled from Gorakhpur was insufficiently predictive for forecasting; however, an inverse association between humidity (but not rainfall or temperature) was observed.ConclusionsDetection patterns confirm seasonal epidemic periods within year‐round endemicity in pigs in eastern Uttar Pradesh. Lack of increasing age‐associated seroprevalence indicates that JEV might not be immunizing in pigs which needs further investigation because models that inform public health interventions for JEV could be inaccurate if assuming long‐term immunity in pigs. Although pigs are considered sentinels for human outbreaks, sufficient timeliness using sero‐surveillance in pigs to inform public health interventions to prevent JEV in people will require more nuanced modelling than seroprevalence and broad climate variables alone.

A scoping review of evidence of naturally occurring Japanese encephalitis infection in vertebrate animals other than humans, ardeid birds and pigs

“…Viral RNA was also detected in pteropodid bats in an earlier study in Indonesia (up to 43% of Balionycterus maculata ; other species were up to 9% prevalence) [50, 51]. The first detection of JEV infection in bats in India was in 2020, associated with a mortality event in which 52 pteropodid bats were found dead in Gorakhpur district, Uttar Pradesh, a province which has a high incidence of JE in people and JEV circulating in domestic pigs [52, 53]. Brain tissue samples from 8 bats were tested by conventional RT-PCR and TaqMan real-time RT-PCR using primers targeting the JEV envelope and NS1 genes.…”