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Bacterial Disease - Colibacillosis

Synonyms

Coli septicemia, Escherichia coli infection

Introduction

Colibacillosis occurs as an acute fatal septicemia or sub-acute pericarditis and air sacculitis. It is a common systemic disease of economic importance in poultry and is seen worldwide.

Etiology and pathogenesis

Escherichia coli are a gram-negative, rod-shaped bacterium normally found in the intestines of poultry and most other animals; although most are nonpathogenic, a limited number produce extra intestinal infections. Pathogenic strains are most commonly of the 02,078 and 01 serotypes. Virulence factors include ability to resist phagocytosis, utilization of highly efficient iron acquisition system, resistance to killing by serum, production of colicins, and adherence to respiratory epithelium.

Large numbers of E.coli are maintained in the poultry house environment through fecal contamination. Initial exposure to pathogenic E.coli may occur in the hatchery from infected or contaminated eggs, but systemic infection usually requires predisposing environmental or infectious usually requires predisposing environmental or infectious causes.

Systemic infection occurs when large numbers of pathogenic E.coli gain access to the bloodstream from the respiratory tract or intestine. Bacteremia progresses to septicemia and death or the infection extends to serosal surfaces, pericardium, joints, and other organs.

Complications by E.coli

Mycoplasmosis, infectious bronchitis, Newcastle disease, hemorrhagic enteritis, and turkey bordetellosis are often complicated by colibacillosis. Poor air quality and other environmental stresses may also predispose to E.coli infections.

Clinical findings and Lesions

Signs are nonspecific and vary with age, organs involved, and concurrent diseases. Young birds dying of acute septicemia have few lesions expect for enlarged, hyperemic liver and spleen with increased fluid in body cavities. Birds that survive septicemia develop subacute fibrinopurulent airsacuulitis, pericarditis, perihepatitis, and lymphocytic depletion of the bursa and thymus. (Usually pathogenic salmonellae produce similar lesions in chicks).

Primary lesion for colibacillosis is air sacculitis. Sporadic lesions include pneumonia, arthritis, osteomyelitis and salpingitis

Diagnosis

Isolation of a pure culture of E.coli from heart blood, liver or typical visceral lesions in a fresh carcass indicates primary or secondary colibacillosis. Consideration should be given to predisposing infections and environmental factors. Pathogenicity of isolates is established when parental inoculation of young chicks or poults results in fatal septicemia or typical lesion within 3 days.

Control

Treatment strategies include attempts to control predisposing infections or environmental factors and early use of antibacterial indicated by susceptibility tests. Commercial bacterins, administered to breeder hens or chicks, have provided some protection against homologous E.coli serotypes.


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