Detection of Lymphocytic Choriomeningitis Virus in House Mouse (Mus musculus) in Brazil

The lymphocytic choriomeningitis virus (LCMV) is an under-investigated rodent-borne arenavirus primarily associated with its natural reservoir, the cosmopolitan rodent <i>Mus musculus</i>. Although widely distributed in mice worldwide, human cases are rare, likely under-reported, and often misdiagnosed. While typically asymptomatic or self-limiting, infection can progress to neurological disease, severe congenital outcomes, or fatal illness in transplant recipients. Despite its public health relevance, this study provides the first detection and characterization of LCMV in Brazil. We analyzed 236 rodent serum samples and 78 tissue samples from synanthropic rodents (<i>Mus musculus</i>, <i>Rattus rattus</i>, and <i>Rattus norvegicus</i>) collected during seven independent expeditions across the state of Rio de Janeiro, Southeastern Brazil. Using ELISAs, IgG anti-LCMV antibodies were detected in 20% of rodents, including two <i>R. rattus</i> (2/10), two <i>R. norvegicus</i> (2/95), and forty-five <i>M. musculus</i> (45/131). The LCMV's RNA was amplified and partially sequenced from fourteen <i>M. musculus</i>, and complete S segment sequences were obtained from two mouse samples. Phylogenetic analyses revealed that these Brazilian strains belong to lineage I, which is composed of strains that induce disease in humans. Our results underscore the importance of implementing integrated surveillance for this zoonosis in Brazil.