Circumstantial evidence has linked a new group of nidoviruses with respiratory disease in pythons, lizards, and cattle. We conducted experimental infections in ball pythons (Python regius) to test the hypothesis that ball python nidovirus (BPNV) infection results in respiratory disease. Three ball pythons were inoculated orally and intratracheally with cell culture isolated BPNV and two were sham inoculated. Antemortem choanal, oroesophageal, and cloacal swabs and postmortem tissues of infected snakes were positive for viral RNA, protein, and infectious virus by qRT-PCR, immunohistochemistry, western blot and virus isolation. Clinical signs included oral mucosal reddening, abundant mucus secretions, open-mouthed breathing, and anorexia. Histologic lesions included chronic-active mucinous rhinitis, stomatitis, tracheitis, esophagitis and proliferative interstitial pneumonia. Control snakes remained negative and free of clinical signs throughout the experiment. Our findings establish a causal relationship between nidovirus infection and respiratory disease in ball pythons and shed light on disease progression and transmission.
Over the past several years, nidovirus infection has been circumstantially linked to fatal respiratory disease in multiple python species, but a causal relationship has not been definitively established. Through experimental infections, our study fulfills Koch's postulates and confirms ball python nidovirus as a primary respiratory pathogen in this species. Our findings will provide veterinarians valuable information for the diagnosis and management of this disease and lay the groundwork for continued scientific investigation of this sometimes fatal disease. Python nidoviruses are members of a growing group of viruses that have been associated with severe respiratory disease, including bovine nidovirus and shingleback lizard nidovirus. The establishment of BPNV as a primary pathogen in pythons is an important step in understanding the pathogenic potential of this emerging group of viruses.