Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 31, 1999
Publication Date: N/A
Interpretive Summary: Turkey osteomyelitis complex (TOC) is a disease of turkeys which occurs mainly at the latest stage of growth, and results in bone, joint, and muscle infections which can affect carcasses which do not appear to be diseased. Previous studies have shown that the injection of turkeys with a compound known to mimic the physical changes caused by stress could cause these turkeys to become susceptible to infection with small amounts of bacteria, which would not ordinarily cause any harm. This study shows that when such turkeys are injected with the compound a second time, the disease is much greater and many of the turkeys have green livers. This is important because the presence of a green liver is currently used to remove these turkeys from the processing plant by food safety inspectors. A surprising finding is that birds which get sick after the second injection are mainly infected with Staphylococcus aureus and not E. coli. This bacteria is the one that is most often isolated from the disease in commercial turkeys. Because S. aureus is present in the environment and doesn't normally cause infections, this finding supports the idea that TOC may be related to the lack of ability of some turkeys to deal with the stresses of their environment.
Technical Abstract: In two separate experiments, turkeys which had survived immunosuppression with dexamethasone (DEX) and air sac inoculation with low numbers of Escherichia coli at 5 wk of age were maintained until 13 wk of age, at which time they were given a second treatment with DEX. All mortalities and birds which were necropsied 8 d and 15 d (Experiment 1) and 21d (Experiment 2) after the last DEX injection were scored for air sacculitis/pericarditis (AS) and turkey osteomyelitis complex (TOC). In both experiments, all of the lesions which characterize TOC were reproduced, including osteomyelitis of the proximal tibia, synovitis/tendonitis, abscesses in the soft tissues and green liver. In Experiment 1, all mortalites after day 7 had TOC lesions while 44% of mortalities had green livers. Staphylococcus aureus was isolated from 90% of all TOC lesions cultured. In Experiment 2 the incidence of mortality, air sacculitis, TOC, and green liver as well as the heterophil/lymphocyte ratio were significantly higher in birds which had previously been treated with DEX but had never been challenged with E. coli as compared to birds which had survived both treatment with DEX and challenge with 25 or 50 cfu of E. coli. Staphylococcus aureus was isolated from 73% of TOC lesions cultured whereas E. coli was isolated from only 5.4%. These studies suggest that TOC incidence may be related to a stress-induced susceptibility to opportunistic infection.