Co-speciation and host-switching drives diversity of picornaviruses and sapoviruses in Malagasy fruit bats

Bats are reservoir hosts for numerous well-known zoonotic viruses, but their broader virus-hosting capacities remain understudied. Picornavirales are an order of enteric viruses that cause disease across a wide range of mammalian hosts, including Hepatitis A in humans and foot-and-mouth disease in ungulates. Host-switching and recombination drive the diversification of Picornavirales worldwide. Picornaviridae and Caliciviridae (families within Picornavirales) have been described in bats across mainland Africa, but surveillance for these viruses has been rare in the Southwest Indian Ocean Islands. Prior work in Madagascar has described numerous bat viruses, some with zoonotic potential, that demonstrate both high identity to and extreme divergence from viruses found in sister bat species in Africa. Using metagenomic Next Generation Sequencing of urine and fecal samples obtained from three species of endemic Malagasy fruit bats (Eidolon dupreanum, Pteropus rufus, and Rousettus madagascariensis), we identify and describe 13 full-length and 38 partial-length genomic sequences within the Picornaviridae and Caliciviridae families (36 picornavirus and 15 Sapovirus sequences). We find evidence that host-switching between Madagascar and mainland African bat picornaviruses and sapoviruses, followed by host-parasite co-speciation, likely shaped the diversification pattens of these novel sequences, with little evidence for cross-species transmission among Malagasy bat species in close contact.