Enteric Integrity

Salmonellosis

Salmonellosis is caused by bacteria of the genus Salmonella and can result in both flock-health and food-safety concerns.

Salmonellosis
01
Disease Overview

Overview

Salmonellosis is caused by bacteria of the genus Salmonella. Poultry are affected by both host-adapted serovars and non-host-adapted serovars, resulting in significant economic losses and important food safety concerns.

Major poultry-associated serovars include

  • Salmonella Pullorum
  • Salmonella Gallinarum
  • Salmonella Enteritidis
  • Salmonella Typhimurium

The disease ranges from severe septicemia in young birds to asymptomatic intestinal colonization in adults.

02
Disease Behavior

Pathogenicity

Following oral infection

  • Bacteria colonize the intestinal tract.
  • Invade intestinal epithelial cells.
  • Spread to the liver, spleen, and other organs.
  • Some serovars establish persistent carrier states.

Disease severity depends on

  • Serovar
  • Bird age
  • Immune status
  • Infectious dose
  • Environmental stress

Young chicks are generally the most susceptible.

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Disease Presentation

Clinical Signs

Young Chicks

  • Depression
  • Reduced appetite
  • White diarrhea (Pullorum disease)
  • Dehydration
  • Stunting
  • Increased mortality

Adult Birds

  • Often subclinical
  • Reduced egg production
  • Reduced fertility and hatchability
  • Occasionally diarrhea

Gross Lesions

  • Enlarged liver and spleen
  • Unabsorbed yolk sac
  • White necrotic foci in liver
  • Enteritis
  • Cecal cores (occasionally)
04
Disease Spread

Transmission & Bacterial Shedding

Transmission

  • Vertical transmission through eggs
  • Horizontal transmission through feces
  • Contaminated litter
  • Feed
  • Water
  • Rodents
  • Wild birds
  • Equipment
  • Personnel

Bacterial Shedding

  • Infected birds may intermittently shed bacteria for weeks or months.
  • Carrier birds are major reservoirs.
  • Environmental persistence facilitates reinfection.
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Identification

Diagnosis and Timeline

Diagnostic Methods

  • Bacterial culture (gold standard)
  • PCR
  • Serotyping
  • ELISA and plate agglutination tests (for surveillance)
  • Histopathology
StageApproximate Time
ExposureDay 0
Intestinal colonization1–3 days
Systemic spread2–5 days
Clinical disease4–10 days
Carrier stateWeeks to months

Differential Diagnoses

  • Escherichia coli infection
  • Necrotic enteritis
  • Coccidiosis
  • Viral enteritis
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Farm Protection

Prevention & Control

Biosecurity

  • Strict breeder flock monitoring
  • Rodent and insect control
  • Hatchery sanitation
  • Clean feed and water
  • All-in/all-out management

Vaccination

  • Live and inactivated vaccines are available for selected Salmonella serovars.
  • Breeder vaccination helps reduce vertical transmission and egg contamination.

Monitoring

  • Routine environmental sampling
  • Drag swabs and boot swabs
  • Hatchery surveillance
  • Serological monitoring
  • Bacteriological culture

Food Safety

Control programs should target both flock health and reduction of carcass and egg contamination to minimize public health risks.