By Autumn Gregg, DVM
Poultry resident
Mississippi State University
In recent years, Enterococcus cecorum has been added to the long differential list for lameness in broilers and broiler breeders. This list also includes viral infections like avian reovirus and Marek’s disease; pathogenic bacteria such as Staphylococcus aureus, Pasteurella multocida and Mycoplasma synoviae; and developmental diseases such as rickets, tibial dyschondroplasia and angular limb deformities.
E. cecorum infections have a significant economic impact on the poultry industry due to factors like poor feed conversion and increased condemnations, costing the industry millions of dollars each year. Moreover, another Enterococcus species — E. faecalis — negatively impacts hatchability.
Given these impacts of Enterococcus spp. in broilers, it is essential to understand more about these bacteria and their effects on the industry.
Enterococcus basics
Enterococcus spp. are gram-positive, ubiquitous microorganisms that are found as commensals in the gastrointestinal tract of chickens. Although their full pathogenesis is not fully known, it is believed that Enterococcus spp. have acquired characteristics that allow them to translocate to various locations, including the heart, liver and vertebrae.
These bacteria have also demonstrated high levels of antibiotic resistance, both naturally occurring and acquired.
There are a few Enterococcus species the poultry industry is concerned about, including E. cecorum and E. faecalis.
E. faecalis has been commonly found in the yolk sac of day-old chicks and at hatcheries. There is suspicion that it is commonly found in hatcheries due to fecal contamination of eggs from the breeder farm. Additionally, E. faecalis is found in the gastrointestinal tract of chickens that are approximately 1 week of age. The true importance of this finding is not yet known because lesions or increased mortality are not always reported when this microorganism is isolated.
E. cecorum is found in the gastrointestinal tract of chickens that are about 4 weeks of age and older. In recent years, it has become more prevalent and shifted from primarily skeletal lesions to more septicemic lesions with significantly increased mortality.
Traditionally, the main clinical signs of an E. cecorum infection were reluctance to walk and hock sitting in a “Harley Davidson” position. This position stems from infection of the free thoracic vertebrae. Today, clinical signs may include reluctance to walk, but birds could die without obvious clinical signs due to septicemia. Males are more affected than females.
The Poultry Research and Diagnostic Laboratory at Mississippi State University keeps a database of the Enterococcus spp. isolated at the laboratory. Species in the database other than E. faecalis and E. cecorum include E. faecium, E. hirae, E. durans and E. gallinarum.
Economic significance of Enterococcus spp.
E. cecorum has been associated with poor feed conversion, increased mortality and condemnations at the processing plants, resulting in increased feed costs and decreased efficiency on the processing line. has also been associated with welfare concerns due to lameness, increasing the number of culls in a flock.
E. faecalis contamination in the hatchery results in embryo death and increased first-week mortality. This impacts hatchability, which has decreased overall in the past decade, and house density. If the contamination is severe enough, it could create a problem where the hatchery cannot fulfill placement orders for that day, resulting in poorer quality chicks being sent to farms.
Current Enterococcus spp. research
Researchers are currently investigating E. cecorum’s pathogenicity and survivability in common poultry substrates, such as litter and hatchery residue, including analyzing survivability in different temperatures and disinfectant susceptibility. This research has been recently completed in other countries but is ongoing in the US. Early results show that both pathogenic and nonpathogenic strains of E. cecorum can survive for at least 4 months on material commonly used in the US poultry industry.
Further research needs to be conducted to evaluate the pathogenicity, survivability and susceptibility of E. faecalis. This microorganism is commonly isolated in chicks but is not always associated with lesions, and there isn’t always an obvious impact on performance.
However, there are times when E. faecalis is the only pathogen isolated when there are reports of increased mortality and poor performance in young birds. This indicates that, like E. cecorum, E. faecalis likely has pathogenic and nonpathogenic strains.
Final thoughts
There are many implications for having Enterococcus spp. in hatcheries and on farms. The high mortality and negative impacts on performance and processing combine to make Enterococcus spp. a major concern for the poultry industry worldwide. Although current research is promising, I believe a collaborative effort to increase the research initiative in Enterococcus spp. is needed to truly tackle this pressing issue in the poultry industry.
Editor’s note: The views expressed in this article are solely those of the author.
