Discovery of an endogenous foamy virus in primitive ruminant chevrotains

Foamy viruses (FV) are complex retroviruses that generally codiverge with their hosts. We identified a novel endogenous FV in the genomes of two mouse-deer species, the first endogenous FV found in Artiodactyla. The phylogenetic inconsistency of viruses and hosts suggested that the viruses might have emerged from cross-species transmission in the past. These findings indicate that ancient FVs may have had a wider range of hosts that remain to be expanded.