Pathological, Immunohistochemical, and Bacteriological Characterization of Salmonellosis in Bearded Dragons (Pogona vitticeps).

Salmonella spp. is a major zoonotic pathogen. Although reptiles are mostly considered subclinical carriers, clinical disease may develop following immunosuppression. Clinical salmonellosis in reptiles has been extensively reported; however, the condition has been rarely described in bearded dragons (Pogona vitticeps). We retrospectively analyzed six cases of salmonellosis in bearded dragons and characterized the pathological, immunohistochemical, and bacteriological findings. Clinical signs and gross findings were mostly non-specific. Histological findings mainly consisted of fibrinonecrotizing enterocolitis (83.3%); necrotizing or granulomatous hepatitis (66.7%); pneumonia including bronchopneumonia or interstitial pneumonia in one case each (33.3%); tubulointerstitial nephritis with tubular necrosis (16.7%); and coelomitis (16.7%). Salmonella enterica subsp. houtenae was cultured in three cases (33.3%), whereas S. enterica subsp. enterica serovar Rissen, S. enterica subsp. enterica serovar Cotham, and S. enterica subsp. diarizonae were cultured in one case each. Intralesional bacteria were detected via immunohistochemistry in kidneys and colon in two cases (33.3%). The predominance of lesions in the intestines and liver likely reflects initial intestinal colonization followed by hematogenous dissemination to the liver. Hepatic lesions are thought to represent different stages along a continuum, progressing from acute necrosis to discrete granuloma formation. Renal and respiratory involvement was infrequent, as reported in other reptile species. Some of the isolated Salmonella subspecies (S. diarizonae and S. houtenae) are well-recognized causes of clinical disease in other reptile species but not previously identified in bearded dragons. This study provides a comprehensive pathological, immunohistochemical, and bacteriological characterization of salmonellosis in bearded dragons, thus raising awareness and assisting in the identification of this condition.