Fowl Typhoid in Chickens: Symptoms, Causes and NPIP Reporting

Salmonella Gallinarum is a host-adapted, non-motile Salmonella that primarily infects chickens and turkeys, causing clinical disease in adults with low susceptibility in newly hatched chicks.

• Horizontal fecal-oral transmission: S. Gallinarum spreads through infected feces contaminating feed, water, and litter. Unlike S. Pullorum, it is primarily a disease of adult birds acquired horizontally in the flock environment.
• Carrier birds: Recovered birds can carry S. Gallinarum in their bile and excrete organisms intermittently for months. Introducing a carrier bird into a naive flock is the most common cause of new outbreaks.
• Contaminated hatching eggs: S. Gallinarum can penetrate the egg shell and infect chicks at hatch, though this is less common than with S. Pullorum.
• Wild bird reservoir: Some wild bird species carry S. Gallinarum subclinically. Open housing that allows wild bird access and fecal contamination of feed is a risk factor.

Fowl typhoid should be suspected in adult flock mortality with anemia, green diarrhea, and the characteristic bronze-green liver at necropsy.

• Necropsy: Enlarged, bronze-green or mahogany-colored liver is the most distinctive finding. The spleen is also enlarged and bronze-colored. Kidneys are pale and swollen.
• Bacteriology: Culture of liver, spleen, or bile on selective Salmonella media confirms S. Gallinarum within 24-48 hours. Biochemical typing differentiates Gallinarum from Pullorum (both are S. Gallinarum biovar, distinguished by dulcitol fermentation).
• NPIP testing: The Whole Blood Test (WBT) and Tube Agglutination Test (TAT) using Pullorum-Typhoid antigen detect antibodies to both S. Pullorum and S. Gallinarum simultaneously.
• Reporting: Positive findings must be reported to the state veterinarian immediately under NPIP requirements.

As with Pullorum disease, the regulatory approach to fowl typhoid is test-and-cull rather than treatment. Antibiotic treatment can suppress clinical signs and reduce acute mortality, but it does not eliminate the carrier state in recovered birds, and treated birds will still test positive on re-testing, prolonging the NPIP certification process.

NPIP test-and-cull protocol: All WBT- or TAT-positive birds are culled without exception. The remaining flock is retested at 21-30 day intervals until two consecutive clean tests are achieved. This process may take 3-6 months in a heavily infected flock. Partial culling (only culling positive reactors while keeping apparent negatives) is insufficient, as seronegative birds can harbor subclinical infection between testing intervals.

Antibiotic use during acute outbreaks: While not the regulatory management tool, sulfonamides (sulfadimethoxine 0.04% in water for 5-7 days) or tetracyclines (oxytetracycline 200 mg/gallon for 5-7 days) can reduce acute mortality when birds are dying rapidly and the economic or welfare cost of waiting for diagnosis confirmation is unacceptable. Use antibiotic treatment as a bridge to diagnosis and NPIP test-and-cull, not as a substitute. Note that chloramphenicol, historically effective, is not approved for use in food-producing animals in the United States.

Environmental decontamination: After complete depopulation, remove all litter, manure, and organic material from housing. Wash all surfaces with detergent, then disinfect with a phenolic disinfectant (effective against Salmonella) or 2% sodium hydroxide solution. Allow housing to remain empty for a minimum of 4-6 weeks before restocking. Outdoor runs contaminated with S. Gallinarum should rest for 6-12 months or have the top layer of soil removed.

Restock only from tested sources: After achieving clean status, restock only with birds from NPIP Pullorum-Typhoid Clean certified flocks. A single carrier bird can restart the cycle in a cleaned facility.

• Participate in NPIP and maintain Pullorum-Typhoid Clean certification. Annual testing is required for exhibition, interstate transport, and sale of hatching eggs in most states.
• Purchase birds only from NPIP Pullorum-Typhoid Clean certified sources. Never introduce birds from auctions or unverified sources.
• Control wild bird access to feed, water, and housing areas. Screen openings and use covered feeders.
• Rodent control: eliminate rodent harborage and food access near poultry areas. Rodents can carry and amplify Salmonella Gallinarum.
• All-in, all-out flock management with complete cleaning and disinfection between flocks prevents cumulative contamination of the environment.