A study of over 600 cases of Enterococcus infections has highlighted trends in the way pathogenic strains of the bacterium are affecting birds at different stages of life.
Enterococcus is a normal inhabitant of the intestinal tract of mammals and birds but can also be associated with systemic disease in poultry. Of Enterococcus species, E. cecorum is a pathogen of particular concern to the poultry industry.
In recent years, E. cecorum has evolved in its presentation within poultry facilities; formerly associated with movement from the intestine to the vertebrae of broiler chickens older than 4 weeks of age, it has increasingly been linked to mortality and lameness in birds 2weeks of age and younger.1
Autumn Gregg, DVM, poultry resident at Mississippi State University, analyzed samples coming into the institution’s poultry diagnostic laboratory between January 2023 and December 2024.2 She presented her results at the 2025 International Poultry Scientific Forum.
In total, Gregg isolated Enterococcus 613 times. Her analysis focused on E. cecorum and E. faecalis, an emerging pathogen of interest mostly seen in hatcheries and young chicks.
Pathogens from different origins
Gregg found that, in both years of the study, E. faecalis was isolated more frequently than E. cecorum. However, most cases of E. cecorum were isolated from birds with visible lesions, whereas E. faecalis largely came from chicks with no visible symptoms and hatchery samples where there had been reports of reduced hatchability.
There were clear age trends differentiating samples of the two Enterococcus species. Gregg primarily saw E. cecorum in birds 3 to 4 weeks old, accounting for 40% of cases in 2023 and 46% of cases in 2024. It was also much more often seen in broilers (69% of cases in 2023 and 57% of cases in 2024).
In contrast, she observed E. faecalis primarily in material from hatcheries such as eggs, fluff and 5- to 7-day-old embryos, as well as 1-week-old birds. These cases from birds aged 1 week old or less accounted for 85% of cases in 2023 and 82% of cases in 2024.
“These findings follow the trend we see when we look at the normal intestinal inhabitancy of Enterococcus throughout the life of the bird, with faecalis being in our younger birds and cecorum being in birds a few weeks of age,” Gregg explained.
Addressing unknowns
The study underscored that pathogenic E. cecorum is a particular threat to growing broilers. Gregg also pointed to a shift from skeletal lesions to septicemic lesions in the high-mortality cases.
Several question marks remain about Enterococcus pathogen transmission and sampling, which will be further explored in new research. Studies will examine survival patterns for E. cecorum and E. faecalis under common rearing conditions, while laboratory work is planned to understand what constitutes an important isolation of E. faecalis, in terms of potential threats to birds’ health and well-being.
1 Higuita J, Arango M, Forga A, Rowland M, Liu J, Wolfenden R, Graham D. 2025. Development of a horizontal transmission model to assess the effects of exposure to pathogenic E. cecorum during the hatching phase in broiler chickens. Poult Sci. 104(1):104488.
2 Gregg A, Thornton JK, Hannay I, Pulido-Landinez M. 2025. Enterococcus genus affecting broiler chickens: evolution of an emerging threat. Presented at: International Poultry Scientific Forum 2025; Atlanta, Ga.
