Avian pathogenic Escherichia coli (APEC) is responsible for a variety of localized and systemic infections in poultry that affect broilers, turkeys and ducks. These infections fall under the term colibacillosis. While some cases result in overt clinical signs, many remain subclinical, making them challenging to detect and manage. In poultry, E. coli can cause a range of subclinical disorders and oxidative stress. This can lead to economic losses and impact bird welfare.
APEC pathotype
E. coli is a versatile bacterium, existing as commensal and pathogenic strains. APEC strains have acquired virulence genes, often clustered in plasmid-borne pathogenicity islands (PAIs). These PAIs define the APEC pathotype and contribute to their ability to cause disease. Additionally, environmental stressors such as poor air quality or other predisposing conditions can weaken birds’ immune systems. This allows commensal E. coli to gain access and cause subclinical infections.
The hidden threat
Subclinical E. coli infections in poultry can result in reduced performance efficiency, compromised welfare and increased susceptibility to other infections. Manifestations often lack clear clinical signs, making early detection challenging. Birds may carry APEC asymptomatically before developing systemic infections.
Clinical signs can include labored respiration, reduced appetite, poor growth and omphalitis, and a noncontagious infection of the navel and/or yolk sac. Postmortem lesions can be pericarditis, airsacculitis, peritonitis or swollen liver and spleen. E. coli is the most common bacteria pathogen that causes septicemia, which is blood poisoning in broilers in the field.
Vertical transmission via the hatchery
APEC also causes additional burdens among broiler breeders, including a decrease in egg production and mortality among birds. There is vertical transmission of APEC to broiler chicks through eggs, resulting in increased first-week mortality and subsequent horizontal transmission at the hatchery. Controlling APEC in broiler breeders reduces first-week mortality in chicks for maintained production level. For that, constant monitoring of the bacterial populations is critical. Research focusing on strategies to mitigate APEC in broiler breeders is one of the best solutions for sustainable broiler production.
Second peak of E. coli
Birds carrying APEC develop systemic infections seen at a later phase. A second peak of E. coli often appears as septicemia around 12–14 days or as bacterial lameness around 25 days.
Antibiotic resistance
Certain E. coli bacteria produce extended-spectrum β-lactamase (ESBL) and become resistant to many antibiotics, limiting treatment options. ESBL-producing E. coli strains are a significant concern in healthcare. APEC is a subgroup of extraintestinal pathogenic E. coli (EPEC) presumed to be zoonotic and to represent an external reservoir for extraintestinal infections in humans, including urinary tract infections (UTIs).
Improved biosecurity
To reduce the introduction and persistence of E. coli in poultry farms, several biosecurity management practices should be applied, including stringent cleaning and disinfection measures. Proper hygiene and biosecurity measures are crucial to prevent potential subclinical diseases in the hatchery and on the farm.
Vaccine development
Developing effective APEC vaccines remains a challenge due to the diversity of APEC serotypes. No single E. coli serogroup can provide complete protection against all APEC strains causing colibacillosis. Research continues to identify novel vaccine targets.
Monoglycerides: an alternative approach
Subclinical E. coli infections in poultry pose significant economic and welfare challenges. Continued research and collaboration are essential to combat these hidden threats and protect both poultry and human health. Organic acids — specifically monoglycerides — serve as valuable tools to control E. coli growth and manage infections caused by it. Eastman’s product portfolio offers promising feed solutions for broiler feed formulations (Eastman Entero-Nova™) and water applications (Eastman Protaq™).
In the next article, we’ll explain how monoglycerides of short- and medium-chain fatty acids play a crucial role in maintaining gut integrity and oxidative stress and preventing the prevalence of E. coli in broilers and broiler breeders.
Sabien Vermaut
Associate AD&TS Manager, Animal Nutrition
