Dexamethasone immunosuppression resulting in turkey clostridial dermatitis: a retrospective analysis of seven studies, 1998-2009.

We have studied the etiology of turkey osteomyelitis complex (TOC) for the past 20 yr and have determined that this syndrome is caused by the inability of some fast-growing male turkeys to cope with production stressors. Although immunosuppressive viruses have often been associated with susceptibility to gangrenous dermatitis (cellulitis), we hypothesize that production stressors alone can also undermine resistance to opportunistic pathogens by both increasing bacterial translocation from the intestine and disrupting the skin's antimicrobial barrier, resulting in subcutaneous lesions referred to as cellulitis and recently named turkey clostridial dermatitis (CD). Some common characteristics between TOC and CD are that they are both caused by opportunistic bacterial species that are prevalent in the environment and are both most common in adolescent male birds. In both diseases the affected birds are often large, healthy, and from the best-performing flocks. Our TOC studies using dexamethasone immunosuppression result in a high incidence of cellulitis lesions in dead turkeys that were given either Escherichia coli or Staphylococcus aureus respiratory challenges. The natural presence of Clostridium spp. in the poultry intestine and environment suggests that they may also have been concomitant pathogens. We suggest that a useful and repeatable model for CD can be developed by focusing on the ability of stress to increase diuresis and wet litter conditions and undermine both intestinal and cutaneous bacterial resistance in fast-growing male turkeys.