Serological Evidence of Lassa Virus in Commensal Rodents from Senegal.

Background Lassa fever, a neglected zoonotic hemorrhagic disease caused by Lassa virus (LASV) and endemic in West Africa, remains a major public health concern linked to rodent exposure. Senegal lies at the western fringe of LASV area, but only one 1988 serosurvey reported low antibody prevalence. Given recent ecological shifts, including expansion of invasive Rattus rattus and Mus musculus , we reassessed LASV exposure in domestic and peri-domestic rodents. Methods We retrospectively analyzed 618 archived rodent sera collected in 2012–2013 from domestic and peri-domestic environments in central and eastern Senegal. Samples were screened by ELISA for LASV IgG and IgM using validated Panadea assays. Spatial mapping and ecological analysis identified seropositivity clusters and potential environmental correlates. Results Eleven rodents (1.8%; 95% CI: 0.9–3.2%) were positive for LASV–specific IgG, with no IgM detected, indicating absence of acute infection. Seropositive animals occurred in five villages clustered along major transport corridors and belonged exclusively to commensal species, Rattus rattus (5%) and Mus musculus (1.1%), within low-diversity rodent communities dominated by invasive taxa. Conclusions This study provides the first update in over three decades on LASV exposure in Senegalese rodents. IgG detection confined to invasive commensal species suggests shifting reservoir dynamics, while reduced diversity at positive sites may indicate a dilution effect. Spatial clustering of seropositive rodents along major transport routes points to low-level but persistent circulation in settings favoring human–rodent contact. These findings highlight the need to integrate rodent surveillance into One Health frameworks to strengthen early warning and regional preparedness.