Genetic and Environmental Factors Contributing to the Pathogenesis of Vertebral Osteomyelitis Caused by Enterococcus cecorum in Broiler Chicken.

Enterococcus cecorum (EC) is the primary cause of Vertebral Osteomyelitis (VO) in poultry, characterized by a hock-sitting posture with legs extended forward. The disease begins with intestinal colonization, where pathogenic strains of E. cecorum establish themselves in the gut within the first week of a bird's lifecycle and translocate to the bloodstream later, reaching the organs, which finally infect the birds' Free Thoracic Vertebrae (FTV). Several factors contribute to the initiation and progression of the disease. Environmental factors such as heat stress, high blood sugar levels, prior infections, overcrowding, and rapid growth conditions weaken immunity and stimulate the emergence of VO. Survivability of the pathogenic strains in the environment and the presence of virulence factors support its pathogenicity. A number of specialized virulence factors are known to be present in pathogenic E. cecorum, supported by the presence of potential mobile elements and resistance genes, which are also mainly present in commensal strains.