Enterococcus cecorum infections in broiler breeders and their offspring: molecular epidemiology

Increased mortality and problems with lameness were reported in Dutch broiler flocks from the year 2008 onwards. Therefore, a field inventory, including 10 affected broiler flocks, nine corresponding broiler breeder flocks and five hatcheries, was carried out. The onset of clinical signs (lameness and increased mortality) started at about 2 weeks of age. The flock mortality varied from 3.1 to 8.1% at slaughter. Post-mortem lesions of broiler flocks were characterized by the occurrence of pericarditis/hydropericardium, arthritis and femoral head necrosis. Enterococcus cecorum was isolated from approximately 30% of the lesions. In the broiler breeders, E. cecorum was not isolated from any of the lesions. However, it was isolated from 31 out of 65 (47%) cloacal swabs, from two out of 65 (3%) oviduct samples, from one out 65 (1.5%) bone marrow samples and from two out of 25 (8%) blood samples. E. cecorum was not isolated from the air samples or dead-in-shell originating from the hatcheries involved. In total, 78 isolates were subjected to further typing by means of tRNA intergenic spacer PCR and confirmed as E. cecorum. The genetic relatedness of these cocci was subsequently studied using pulsed-field gel electrophoresis. The banding patterns of approximately 68% of E. cecorum isolates originating from parent stock flocks were clonal to one or more isolates of the same or other parent flocks. In contrast, isolates originating from their diseased offspring showed much greater genetic variation. Therefore, the vertical transmission of E. cecorum could not be demonstrated.