By Dr. Luke B. Borst
Enterococcal spondylitis (ES), often called kinky back in the industry, is an infection of the vertebrae of broilers caused by pathogenic Enterococcus cecorum (EC). Outbreaks of pathogenic Enterococcus cecorum (EC) infection continue to cause significant economic losses to broiler producers throughout the US; however, basic characteristics of the disease remain unclear. Prior to this study, the stage when EC colonized the gut or entered the blood stream (sepsis) was unknown.
It also was unclear if either gut challenge (co-infection) or predisposing damage to the spine was required for a bird to manifest disease. In this study, we compared flocks on farms where EC-associated disease caused by pathogenic EC had been a repeated problem (case farms) with flocks on farms where the disease had never occurred (control farms).
Specifically, our two main objectives were to 1) compare flocks from case/control farms for intestinal co-infections, and 2) compare case/control farms for management practices and presence of pathogenic EC in the farm environment.
Findings in this study have closed major gaps in our understanding of EC-associated disease. We determined that gut colonization and sepsis occur during weeks 1-3 of life. This is critical information, as it indicates that vaccination of breeder hens with an inactivated vaccine may help protect progeny (broilers) from the disease. We are pursuing this strategy in a follow-up USPOULTRY grant that is currently in progress. This finding also shows that the disease process starts 2-3 weeks before clinical signs appear in the flock, which helps explain why treatment of affected flocks with antibiotics has not been beneficial.
When we looked for predisposing factors, we found that significant concurrent gut infections (gut challenges) were not required for birds to manifest EC-associated disease. However, it remains to be seen if concurrent gut challenge can make EC-associated disease worse. In contrast, osteochondrosis dessicans (OCD - a defect in the cartilage covering bone in a joint) lesions were identified in the spines of affected birds, which we believe predispose them to EC-associated disease and may explain why the disease primarily affects the spine. OCD lesions were common in lame birds suggesting that OCD may contribute to lameness in broilers even when there is no EC infection.
Finally, we discovered that EC does not persist in the environment when chickens are not present on the farm, and no specific management practice was clearly associated with EC status.
Click here to see more...