Simian Foamy Virus Prevalence and Evolutionary Relationships in Two Free-Living Lion Tamarin Populations from Rio de Janeiro, Brazil.

Simian foamy virus (SFV) is a retrovirus that infects primates. However, epidemiological studies of SFV are often limited to captive populations. The southeastern Brazilian Atlantic Forest is home to both an endemic, endangered species, , and an introduced species, , to which no data on SFV exist. In this study, we assessed the molecular prevalence of SFV, their viral load, and their phylogenetic relationship in these two species of primates. Genomic DNA was extracted from 48 oral swab samples of and 102 of . Quantitative PCR (qPCR) was performed to diagnose SFV infection and quantify viral load. SFV prevalence was found to be 23% in and 33% in . No age-related differences in prevalence were observed; however, showed a higher mean viral load (3.27 log10/10 cells) compared to (3.03 log10/10 cells). The polymerase gene sequence (213 pb) of (SFVlro) was clustered within a distinct SFV lineage found in The estimated origin of SFVlro dated back approximately 0.0836 million years ago. Our study provides the first molecular prevalence data for SFV in free-living populations while offering insights into the complex evolutionary history of SFV in American primates.