Pathogenic Bacteria in the Gastrointestinal Tract of Poultry

Characteristics of E. coli

E. coli remains a significant pathogen today. Common pathogenic strains found in poultry include 01, 02, and 078. In Thailand, the 078 strain is predominantly associated with poultry diseases. It can affect broiler chickens at all growth stages and is commonly found in the intestines.

As a gram-negative bacterium, E. coli becomes particularly severe in broilers aged 4-5 weeks, leading to higher-than-normal mortality rates. Growth rates in infected chickens are often below standard due to disruptions in digestion and nutrient absorption. This results from the bacterium damaging the small intestine lining, causing detachment, inflammation, and further weakening of the intestinal barrier. E. coli colonizes the small intestine, multiplies, and more easily enters the bodys systems, especially when chickens also suffer from coccidiosis.

Modes of E. coli Transmission

Chickens can contract E. coli through various routes:

Vertical transmission via eggs: This is a common mode of transmission, leading to high mortality rates in chicks shortly after hatching.

Eggshell contamination: E. coli from chicken feces can contaminate the eggshell and penetrate inside.

Environmental exposure: The bacteria can spread through dust in poultry houses, bedding material, excreta from other chickens, or contaminated drinking water.

Impacts and Contributing Factors
The Veterinary Pharmaceutical Business Association reports that E. coli infections in chickens often manifest as colibacillosis, typically occurring after the birds experience stress or immune suppression.

Factors contributing to stress and disease include: Vaccination and concurrent infections: Chickens with MG infections or those vaccinated for Newcastle disease, infectious bronchitis, or infectious laryngotracheitis may be at higher risk.

Compromised immunity: Conditions like Gumboro disease (infectious bursal disease) or exposure to fungal toxins can weaken the immune system.

Environmental stressors: Fluctuating weather, extreme temperature differences between day and night, poor hatchery practices, high ammonia levels, excessive moisture, and inadequate ventilation can all contribute to stress and increase susceptibility to disease.

Preventive Measures and Solutions

To address the dual challenge of E. coli infections and stress-induced immune suppression, both factors must be managed effectively:

1. Eradicate E. coli from the production system:
- Maintain strict hygiene in poultry houses.
- Disinfect thoroughly between production cycles.

2. Minimize stress in chickens:

- Avoid overcrowding and ensure adequate access to clean water and balanced nutrition.
- Supplement minerals and vitamins during hot weather to reduce stress.
- Promote gut health with beneficial probiotics to maintain a healthy microbial balance. Probiotics can help suppress pathogenic bacteria.

Modern poultry farming must also reduce and eventually eliminate the use of antibiotics to foster sustainable practices. When properly managed, chickens will achieve robust health, avoid secondary infections, and meet standard growth performance metrics. This ultimately ensures higher profitability for poultry businesses.