Ball Python Nidovirus: a Candidate Etiologic Agent for Severe Respiratory Disease in Python regius

Stenglein, Mark D.; Jacobson, Elliott R.; Wozniak, Edward J.; Wellehan, James F. X.; Kincaid, Anne; Gordon, Marcus; Porter, Brian F.; Baumgartner, Wes; Stahl, Scott; Kelley, Karen; Towner, Jonathan S.; DeRisi, Joseph L.

In comparison to the histology of normal snake lung, all nine snakes had a proliferative interstitial pneumonia of various severities (Table 1 ). In some cases, inflammatory cells were primarily around the terminal smooth muscle bundle of each septum that projected into the central lumen of the lung ( Fig. 2A and B) . Hyperplastic alveolar cells completely proliferated over capillary beds that are normally distributed at the surface of the primitive faveoli ( Fig. 2C and D) . Epithelial cells were tall and columnar with abun- dant apical mucus production (mucous metaplasia). Periodic acid-Schiff (PAS) and alcian blue staining were positive, consistent with the presence of mucopolysaccharides. Heterophils, lymphocytes, and in some cases macrophages infiltrated the interstitium of the pulmonary septa ( Fig. 2D ) and often were seen in air passageways along with sloughed epithelial cells. In deeper areas of the faveolar spaces, the lung was histologically normal. In more severe cases, the proliferative changes occurred diffusely throughout the lung and were seen from the proximal to distal surfaces lining faveolar structures. Three snakes had mild to marked bronchial epithelial hyperplasia, with mild to moderate smooth muscle hypertrophy of the terminal muscle bundles. In these cases, the bronchus-associated lymphoid tissue was mildly to moderately hyperplastic. Sections of lungs of two cases were stained with Warthin-Starry stain and Brown-Hopps Gram stain; there was no positive staining for bac-teria between cilia and microvilli of pneumocytes overlying muscle bundles. Three of five nasal cavities that were examined revealed mild subacute rhinitis/sinusitis. The vomeronasal organ in one snake was almost obliterated by foamy macrophages. Ziehl-Neelsen acid-fast staining was negative for acid-fast bacteria, and methenamine silver staining was negative for yeast and hyphae. Three cases had mild to moderate stomatitis/pharyngitis. The changes seen in the respiratory tract were consistent with a viral infection.