Lassa Fever Virus Ecology, Multimammate Rat Dynamics, and Community Exposure Pathways in Enugu and Ebonyi States

Lassa fever remains endemic in Nigeria's South East zone, yet the precise ecological dynamics governing Mastomys natalensis reservoir density, viral shedding patterns, and community exposure routes have not been fully characterized. This study investigated Lassa fever virus ecology, multimammate rat population dynamics, and community exposure pathways in Enugu and Ebonyi States. A longitudinal multi-site study was conducted over 18 months. Live-trap transects were established at 20 sites across farming communities, forests, and peri-domestic environments. Trapped rodents were identified morphologically and genetically, and organ samples were tested for Lassa virus by reverse transcriptase PCR and antigen-capture enzyme-linked immunosorbent assay. A seroprevalence survey was conducted among 300 community residents, and exposure pathway analysis was performed using structured questionnaires and network contact tracing from confirmed cases. Mastomys natalensis constituted 73.4% of all captured rodents. Lassa virus prevalence in trapped rodents was 18.2%, with significant seasonal variation peaking in the dry season between November and February. Human seroprevalence was 14.7%, with highest rates in agricultural workers and those reporting rodent contact in grain stores. Household grain storage and farming activities were the strongest exposure pathway predictors. Genome phylogenetics of rodent and human isolates confirmed local strain circulation without recent importation. The study provides original ecological and epidemiological data on Lassa fever dynamics in South East Nigeria, with implications for targeted rodent control, community education, and early warning surveillance systems. Keywords: Lassa fever, Mastomys natalensis, viral ecology, South East Nigeria, community exposure