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United States Department of Agriculture

Agricultural Research Service

Title: The Effects of Dexamethasone Immunosuppression on Turkey Osteomyelitis Complex in An Experimental Escherichia Coli Respiratory Infection

Authors
item Huff, Geraldine
item Huff, William
item Balog, Janice
item Rath, Narayan

Submitted to: Journal Of Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 1997
Publication Date: N/A

Interpretive Summary: Turkey osteomyelitis complex (TOC) is a disease characterized by the presence of bone, joint, and muscle infections in processed turkeys. The effect of stress on the ability of turkeys to fight these infections was studied by injecting birds with a compound known to mimic the physical changes caused by stress before injecting their respiratory systems with bacteria. Bacterial respiratory infections are an important cause of disease in turkeys, but have not previously been shown to lead to TOC lesions. When small amounts of bacteria were injected into the respiratory systems of non-stressed turkeys, there was little disease produced; however, when small amounts of bacteria were injected into stressed turkeys, the incidence of mortality, respiratory disease, and TOC was increased. The ability to reproduce TOC lesions in turkeys is an important step in finding treatments to help in the prevention of the disease.

Technical Abstract: Three hundred male turkeys were maintained in floor pens for 5 wk at which time half of the birds were given 3 intramuscular injections of 2 mg/KG BW of dexamethasone (DEX) on alternating days. On the day of the third DEX injection, the left thoracic air sac of each bird was injected with sterile tryptose phospate broth (TPB) or with TPB containing approximately 1 * 10**2, 1* 10**3, 1 *10**4, or 1 * 10**5 colony-forming units of Escherichi coli. Birds were necropsied at 14 and 15 days post-challenge and were scored for air-sacculitis/pericarditis (AS) and turkey osteomyelitis complex (TOC). Cumulative mortality and AS score were both increased by either DEX treatment or E. Coli. Although TOC incidence was significantly increased by the lowest titer of E. Coli inoculation, increasing the number of bacteria inoculated did not increase TOC incidence due to increased mortality before TOC lesions developed. DEX treatment by itself increased TOC incidence and there was a synergistic interaction between DEX treatmen and E. Coli on TOC incidence. DEX treatment and E. Coli both significantly decreased BW. Relative weights of liver, heart, and spleen were significantly increased by both E. Coli and DEX, whereas both treatments significantly decreased relative bursal weight. The number of positive bacterial isolations from tissue and the heterophil to lymphocyte ratio were increased by both DEX treatment and E. Coli challenge. These results suggest that stress-induced immunosuppression may be involved in the etiology of TOC, and that bacterial respiratory infection can lead to the development of TOC lesions.

Last Modified: 7/25/2014
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