Enterococcus hirae–Associated Endocarditis Outbreak in Young Broiler Breeders of the Female Line

Enterococci infections may result in acute and chronic disease. Lesions, such as osteomyelitis, arthritis, or endocarditis, depend on the <i>Enterococcus</i> species involved. In this case report, an outbreak of <i>Enterococcus hirae</i>-associated endocarditis affecting young broiler breeders is presented. On a rearing farm with 46,500 broiler breeders, a slight increased mortality (1.02%-1.42%) within the female line was observed between 2 and 6 wk posthatch (ph). Between days 12 and 47 ph, 256 birds were pathologically examined, and bacteriologic samples were taken. In 191 (51.8%) of the examined female line chickens, endocarditis was observed on at least one of the atrioventricular valves, while no endocarditis was diagnosed in chickens of the male line (<i>n</i> = 65). <i>Enterococcus hirae</i> was isolated from 64.4% of the bone marrow samples and from two heart samples taken from chickens of the female line. <i>Enterococcus hirae</i> was not isolated from samples taken from the male line. In addition, natural antibody titers (immunoglobulin G) were significantly higher in serum of the female line compared with the male line. This case gives an overview of gross lesions and bacteriology of <i>E. hirae</i> affecting only the female line of broiler breeders.