Differential disease susceptibility in experimentally reptarenavirus infected boa 1 constrictors and ball pythons

26 Inclusion body disease (IBD) is an infectious disease originally described in captive snakes. It has 27 traditionally been diagnosed by the presence of large eosinophilic cytoplasmic inclusions, and is 28 associated with neurological, gastrointestinal and lymphoproliferative disorders. Previously, we 29 identified and established a culture system for a novel lineage of arenaviruses isolated from boa 30 constrictors diagnosed with IBD. Although ample circumstantial evidence suggested that these viruses, 31 now known as reptarenaviruses, cause IBD, there has been no formal demonstration of disease 32 causality since their discovery. We therefore conducted a long-term challenge experiment to test the 33 hypothesis that reptarenaviruses cause IBD. We infected boa constrictors and ball pythons by cardiac 34 injection of purified virus. We monitored progression of viral growth in tissues, blood, and 35 environmental samples. Infection produced dramatically different disease outcomes in snakes of the 36 two species. Ball pythons infected with Golden Gate virus (GoGV) and with another reptarenavirus 37 displayed severe neurological signs within two months and viral replication was only detected in 38 central nervous system tissues. In contrast, GoGV-infected boa constrictors remained free of clinical 39 signs for two years despite high viral loads and the accumulation of large intracellular inclusions in 40 multiple tissues including the brain. Inflammation was associated with infection in ball pythons but not 41 in boa constrictors. Thus, reptarenavirus infection produces inclusions and inclusion body disease, 42 although inclusions per se are neither necessarily associated with nor required for disease. Although 43 the natural distribution of reptarenaviruses has yet to be described, the different outcome of infection 44 may reflect differences in geographical origin. 45