Fatal gangrenous dermatitis with necrotising cellulitis, fasciitis and secondary myonecrosis associated with clostridial organisms in a captive greater rhea (Rhea americana)

Clostridial gangrenous dermatitis is an acute, often fatal, necrotising soft-tissue disease well recognised in commercial poultry, but it is rarely documented in non-poultry avian species and has not been reported as a peer-reviewed case in greater rheas (Rhea americana). This report describes a fatal case of gangrenous dermatitis with severe necrotising cellulitis, fasciitis and secondary myonecrosis associated with clostridial organisms in an adult captive female greater rhea. The bird developed acute anorexia, depression, inability to stand, loose stools and a focally extensive, irregular, moderately demarcated lesion in the dorsal pelvic region, characterised by dark-red to black discolouration, multifocal bluish-green areas and feather loss shortly after transport with two other adult rheas, and was submitted for post-mortem examination less than 1 h after death. Grossly, the dorsal pelvic, pericloacal, tail-base and proximal hindlimb regions had extensive necrotising dermatitis, emphysematous cellulitis and fasciitis, and haemorrhagic myonecrosis of the affected skeletal muscle. Histologically, there was severe acute necrotising dermatitis, cellulitis, fasciitis, panniculitis and myonecrosis, with oedema, fibrin, haemorrhage, gas spaces, heterophilic inflammation and numerous bacilli within necrotic subcutaneous and fascial tissues. Impression smears contained numerous rod-shaped bacilli compatible with spore-forming bacteria. Anaerobic culture of affected deep subcutaneous/fascial tissue yielded Clostridium perfringens type A, C. septicum and C. chauvoei, with PCR confirmation performed on bacterial growth/isolates. Histological Gram staining demonstrated Gram-positive rod-shaped bacilli within the necrotic tissue matrix. Aerobic culture and Gram staining of cytological smears were not performed. The findings support a fatal gangrenous dermatitis with necrotising cellulitis, fasciitis and secondary myonecrosis associated with clostridial organisms, although the involvement of aerobic or facultative co-pathogens cannot be completely excluded. This case expands the pathological spectrum of gangrenous soft-tissue disease in ratites and indicates that gangrenous dermatitis with deep cellulitis, fasciitis and secondary myonecrosis should be considered in captive greater rheas with acute emphysematous and necrohaemorrhagic soft-tissue lesions.