Assessing the endemicity of Japanese Encephalitis in Central India: A comprehensive study of human and animals in Madhya Pradesh.

Abstract

Background objectives: With an annual prevalence of 2,000 cases, India has the highest global burden of Japanese Encephalitis (JE). However, the distribution of the disease is not uniform across the country, wherein the states and districts considered endemic are prioritized for vaccination and other control measures. The central Indian state of Madhya Pradesh (MP), which is not yet considered JE-endemic, possesses multiple agents, hosts, and environmental risk factors and is geographically close to several hotspots of transmission. In this study, we explored the potential endemicity of JE in MP by estimating its prevalence in acute encephalitis syndrome (AES) cases, examining its geospatial and temporal distribution, and demonstrating evidence of viremia in known animal reservoirs.

Methods: A total of 761 human samples were analyzed using an ELISA kit to detect anti-JEV IgM antibodies. Nested and hemi-nested RT-PCR targeting the C-prM region were employed for 93 ELISA-positive human samples, as well as 100 swine and 99 equine samples.

Results: We observed a prevalence of 13% (99 out of 761) of JE in AES cases, predominantly affecting the pediatric population (73.74%) without any gender predisposition. We found JE viremia in 7% of swine and 8% of equine samples as potential animal reservoirs. Interpretation & conclusion: In conclusion, the study revealed a geospatial distribution of the virus in reservoirs and/or hosts across 22 districts, with high- and intermediate-burden districts clustering near the state's border with other JE-endemic states. The temporal distribution indicated that the virus circulated throughout the year.