Nidoviruses: Emerging or Previously Missed Pathogens of Pythons

Jacobson, Elliot R.

College of Veterinary Medicine

University of Florida

Gainesville, FL USA

Since the 1990s, veterinarians have been aware of an infectious respiratory disease of unknown cause in ball pythons (Python regius) that can be fatal. Affected ball pythons typically have oro-pharyngeal areas of necrosis along with severe diffuse respiratory disease. Necropsies were performed on 9 snakes with respiratory disease from collections in 5 states in the US, and multiple tissues were collected for light microscopy and molecular diagnostics. Samples of lung from 2 cases were submitted for transmission electron microscopy (TEM). Eight of nine snakes had tracheitis, and all nine snakes had a proliferative moderate to severe interstitial pneumonia. Using TEM, a filamentous virus was observed developing in the cytoplasm of pneumocytes and mature virions were released from the surface of infected cells into the adjacent air passageways. Using PCR, frozen tissues were tested for viruses of the families Paramyxoviridae, Reoviridae, Rhabdoviridae, and Filoviridae. No positive samples were found for any members of these families. Whereas the agent could not be identified by traditional molecular diagnostic methods, metagenomic sequencing was used to identify the genome of a novel virus in the order Nidovirales (Stenglein et al, 2014. mBio 5: e01484-14). Around the same time, a similar virus was identified in ball pythons in a collection in NYS, USA (Uccellini et al, 2014. Virology Journal 11: 144) and in an Indian python (Python molurus) in a zoo in Germany (Bodewes, 2014. Journal of General Virology 95: 2480-5), all having respiratory disease. Subsequently a related virus was found in green tree pythons (Morelia viridis) with respiratory disease from multiple collections in Florida (Jacobson and Stenglein, Unpublished findings). Most recently a novel nidovirus was identified in wild shingleback skinks (Tiliqua rugosa) in Australia (O’Dea, 2017. PloS One 11:e0165209. doi:10.1371/journal.pone.0165209).