Fowl Typhoid in Chickens: Causes, Symptoms, Diagnosis, and Prevention

By: Poultry Health Resource | Last Updated: May 2026
Keywords: fowl typhoid chickens, Salmonella Gallinarum poultry, fowl typhoid symptoms, fowl typhoid treatment, NPIP fowl typhoid, reportable poultry disease, Salmonella gallinarum diagnosis, poultry flock health

What Is Fowl Typhoid?

Fowl typhoid is one of the oldest and most destructive bacterial diseases in poultry history — and despite being eradicated from commercial flocks in the United States and several other developed nations, it remains a serious, ongoing threat to poultry industries around the world, and a real risk to backyard flocks everywhere.

Fowl Typhoid (FT) is a severe, systemic (whole-body) bacterial disease caused by Salmonella enterica serovar Gallinarum — commonly shortened to Salmonella Gallinarum or simply SG. The bacteria invade the bloodstream and spread throughout the body, attacking major organs including the liver, spleen, and ovaries, and causing mortality rates that can devastate an entire flock within days.

According to the Merck Veterinary Manual, among all the Salmonella-related diseases that affect poultry, fowl typhoid is considered one of the most economically important worldwide. A 2024 review published in Antibiotics (MDPI) confirmed that Salmonella Gallinarum remains the cause of severe systemic disease in poultry globally, with outbreaks continuing to be reported in developing countries across Asia, Latin America, the Middle East, and Africa.

Important for U.S. Flock Owners: Fowl typhoid is a federally reportable disease in the United States. If you suspect your flock is infected, you are legally required to notify your state veterinarian immediately.

Understanding the Bacteria: Salmonella Gallinarum and Its Cousin, Pullorum

To understand fowl typhoid, it helps to know a little about the bacterial family it belongs to.

Salmonella Gallinarum is part of a broader group called Salmonella enterica subspecies enterica serovar Gallinarum — a mouthful of scientific naming that tells us this is a highly specific, poultry-adapted strain of Salmonella. Unlike the Salmonella strains most people associate with food poisoning in humans (such as S. Typhimurium or S. Enteritidis), Salmonella Gallinarum is host-specific — it is adapted almost exclusively to birds and does not typically cause disease in humans.

Salmonella Gallinarum has two biovars (biological variants) that cause two distinct but related diseases:

  • Biovar Gallinarum → causes Fowl Typhoid (FT) — the focus of this article
  • Biovar Pullorum → causes Pullorum Disease (PD) — primarily a disease of young chicks

The 2024 Antibiotics review (Farhat et al., Agronomy and Veterinary Institute Hassan II, Morocco) explains that while both biovars can be egg-transmitted and produce similar lesions, S. Gallinarum has a much greater tendency to spread rapidly among growing and mature flocks — making fowl typhoid far more dangerous to adult birds than pullorum disease typically is.

Who Gets It? Species and Age Susceptibility

Fowl typhoid primarily affects:

  • Chickens — most severely affected
  • Turkeys
  • Guinea fowl, pheasants, peafowl, and quail
  • Many wild and game birds

Age matters — but not in the way you might expect. Unlike many poultry diseases that are worst in very young birds, fowl typhoid is uniquely dangerous to adult and near-adult birds, which distinguishes it from most other poultry diseases. This is what makes it so economically devastating — it can wipe out laying flocks or breeding stock that represent years of investment.

That said, young chicks hatched from infected eggs can also develop severe disease and die within the first weeks of life. In these young birds, the clinical picture closely resembles Pullorum disease.

How Does Fowl Typhoid Spread?

Understanding the routes of transmission is critical for prevention. Salmonella Gallinarum spreads through multiple pathways:

Vertical Transmission (Egg to Chick)

One of the most insidious routes. Infected hens can pass the bacteria directly into their eggs before the shell is formed. Chicks that hatch from these eggs are infected from the moment of birth, and they can spread the disease throughout a hatchery before anyone realizes something is wrong.

Horizontal Transmission (Bird to Bird)

This is where fowl typhoid really distinguishes itself. The bacteria spreads rapidly between birds in a flock through:

  • Fecal-oral route — droppings contaminate feed, water, litter, and soil
  • Direct contact between infected and healthy birds
  • Oral secretions from sick birds

Environmental Persistence

Salmonella Gallinarum can survive for extended periods in contaminated litter, soil, water, and housing — meaning a premises that has had an outbreak can remain a source of infection for subsequent flocks if not thoroughly decontaminated.

Carriers

Recovered birds can become silent carriers — appearing healthy while continuing to shed bacteria in their droppings and contaminating their eggs. This makes it extremely difficult to know whether a flock is truly clean without laboratory testing.

Wild Birds, Rodents, and Fomites

Wild birds, rodents, insects, contaminated equipment, boots, and clothing can all introduce bacteria onto a previously clean farm. This is a key reason why biosecurity is so critical.

Signs and Symptoms: What to Watch For

Fowl typhoid can appear suddenly and progress rapidly. The clinical presentation varies with age.

In Adult and Growing Birds

Adult birds showing clinical fowl typhoid typically display:

  • Depression and lethargy — birds appear dull, stand hunched, and separate themselves from the flock
  • Pale, anemic comb and wattles — the comb and wattles turn pale or even white due to severe anemia caused by the infection destroying red blood cells
  • Greenish-yellow diarrhea — one of the most distinctive and consistent signs; the abnormal color reflects bile pigments from liver damage
  • Sticky feces pasted around the vent (sometimes called “pasty butt”) — a sign of diarrhea and dehydration
  • Increased thirst and dehydration
  • Labored or rapid breathing — indicating systemic illness
  • Sudden, dramatic drop in egg production in laying flocks
  • Increased mortality — in acute outbreaks, death rates can be rapid and high

The Merck Veterinary Manual notes that in severe cases, the liver shows distinctive enlargement with multiple white, coalescing necrotic lesions — one of the most recognizable findings on post-mortem examination. The spleen is also typically enlarged, and the ovaries in laying hens may show regressing, flaccid eggs with prominent blood vessels.

In Young Chicks (Hatched from Infected Eggs)

  • Weakness, poor appetite, and stunted growth
  • Chalky white or pasty droppings
  • Shrill chirping or peeping sounds (a sign of distress)
  • Swollen joints (hocks or wings in some cases)
  • High mortality in the first few weeks of life

Sudden Death

In acute outbreaks — particularly in adult birds experiencing fowl typhoid for the first time — birds may die with few or no prior visible warning signs. This sudden-death presentation, combined with the rapid spread through a flock, is one of the hallmarks of severe fowl typhoid outbreaks.

What Happens Inside the Bird: Pathology

For those interested in the science, here is what veterinarians find on post-mortem examination (necropsy) of birds that have died from fowl typhoid:

  • Liver — greatly enlarged, often bronze or bile-stained in color; may contain multiple white or yellow necrotic (dead tissue) lesions throughout
  • Spleen — enlarged and congested
  • Heart — may show petechial (pinpoint) hemorrhages on the heart muscle and surrounding fat tissue
  • Ovaries — in laying hens, eggs may be shriveled, discolored, or regressing; blood vessels on the ovarian tissue are often prominent
  • Intestines — inflammation of the gut (enteritis) with reddened, thickened walls
  • Kidneys — often pale and swollen
  • Caeca — in young birds, yellowish cecal plugs (firm material in the blind gut pouches) may be present

These pathological findings give veterinarians important clues — but definitive diagnosis always requires laboratory confirmation.

Diagnosis: Confirming Fowl Typhoid

Because the symptoms of fowl typhoid overlap significantly with other diseases — including Pullorum disease, Newcastle disease, and infectious bursal disease — laboratory diagnosis is essential. Never attempt to treat or respond to a suspected fowl typhoid outbreak without veterinary guidance and confirmed test results.

1. Bacterial Culture and Isolation (Gold Standard)

A sample of blood, liver, spleen, or other affected tissue is cultured in a laboratory to grow and identify the bacteria. Salmonella Gallinarum has characteristic growth patterns that allow trained microbiologists to identify it. The Merck Veterinary Manual states that confirmation of S. Gallinarum is through isolation and identification — no other diagnostic method replaces this step.

2. Serotyping

Once Salmonella bacteria are isolated, serotyping identifies the specific serovar (Gallinarum vs. other Salmonella types). This is required because different Salmonella serovars have different significance, public health implications, and regulatory responses.

3. Whole Blood Plate Agglutination (WBPA) Test

This rapid field test involves mixing a drop of the bird’s blood with a standardized antigen on a slide or plate. Clumping (agglutination) indicates the bird has antibodies against S. Gallinarum or S. Pullorum. The WBPA test is widely used for flock screening under the National Poultry Improvement Plan (NPIP) in the United States, as it can test large numbers of birds quickly. However, it cannot distinguish between antibodies from S. Gallinarum and S. Pullorum, so positive results require follow-up culture to confirm the specific biovar.

4. PCR (Polymerase Chain Reaction) Testing

Modern molecular testing can detect Salmonella Gallinarum DNA directly from tissue samples, often more quickly than traditional culture. PCR is increasingly used in diagnostic laboratories as a faster, highly sensitive screening tool.

5. Whole Genome Sequencing (WGS)

At the cutting edge of diagnostic science, WGS is now being used to characterize S. Gallinarum strains in detail — tracing outbreak origins, identifying virulence genes, and detecting antibiotic resistance genes. A global genome dataset published in PubMed in 2024 compiled 574 well-characterized S. Gallinarum samples from 1920 to 2024, providing an unprecedented resource for understanding how this pathogen evolves and spreads internationally.

Treatment: A Complex and Regulated Area

Treatment of fowl typhoid is significantly more complicated than treatment of many other poultry diseases, for two important reasons:

1. Antibiotic Resistance Is Growing A 2023 genomic analysis published in Genes (MDPI) of Colombian S. Gallinarum strains identified 26 chromosome-located antibiotic resistance genes in the bacteria — mostly efflux pumps that physically pump antibiotics out of bacterial cells before they can work. Mutations in key genes (such as gyrA and gyrB) were also found, conferring resistance to fluoroquinolone antibiotics.

A 2024 PMC study (Microbiology Society) found ongoing antibiotic resistance patterns in S. Gallinarum and S. Pullorum isolates, with concern growing that antibiotic-free farming trends — while positive for reducing resistance — may be increasing disease vulnerability in some flocks.

2. Treatment Can Create Carriers This is critically important: the Merck Veterinary Manual and the eXtension Poultry Health Program (USDA-supported) note that treatment is generally not recommended for Pullorum disease because treated birds often recover clinically but become permanent, silent carriers — shedding bacteria in eggs and droppings indefinitely, perpetuating the disease in the flock and in any flock they contact. The same concern applies to fowl typhoid.

When treatment is attempted under veterinary supervision, options that have been used include:

  • Sulfonamides (e.g., sulfadimethoxine)
  • Tetracyclines
  • Fluoroquinolones (where not yet resistant and where legally permitted)
  • Furazolidone — historically used but now banned in food animals in many countries including the U.S.

The key takeaway: treatment suppresses the disease but rarely eliminates the infection from the flock. In regulated countries including the United States, the standard response to a confirmed fowl typhoid outbreak is depopulation (destruction of the entire flock), followed by thorough decontamination of the premises.

The National Poultry Improvement Plan (NPIP): America’s Defense Against Fowl Typhoid

For U.S. flock owners, understanding the National Poultry Improvement Plan (NPIP) is essential. This federal-state cooperative program, administered by USDA-APHIS (Animal and Plant Health Inspection Service), was originally developed in 1935 specifically to eradicate Pullorum disease and fowl typhoid from U.S. commercial poultry.

According to Clemson University’s NPIP overview, over 95% of the U.S. breeding and hatchery industry participates in the NPIP. The program requires:

  • Regular flock testing for S. Gallinarum and S. Pullorum
  • Certification of breeding flocks and hatcheries as “U.S. Pullorum-Typhoid Clean”
  • Mandatory reporting of any positive test results
  • Quarantine and depopulation of infected flocks
  • Thorough decontamination before restocking

The Merck Veterinary Manual credits the NPIP with the eradication of fowl typhoid from domestic commercial poultry flocks in the United States — a remarkable public health and agricultural achievement.

For backyard flock keepers: Many states require NPIP certification or testing for birds sold, traded, exhibited at fairs, or transported across state lines. Check with your state veterinarian for the specific requirements in your state.

Prevention: Your Best Strategy

Buy From NPIP-Certified Sources

This is the single most important step for U.S. flock owners. Always purchase birds, hatching eggs, and chicks from hatcheries or breeders that are NPIP-certified “U.S. Pullorum-Typhoid Clean.” The Merck Veterinary Manual and U.S. extension programs are emphatic on this point: never introduce birds from untested or unknown sources into your flock.

Biosecurity

  • Limit farm visitors and require disinfection of footwear
  • Use dedicated clothing for working with your birds
  • Control rodents and wild bird access to housing
  • Disinfect all equipment between uses

Sanitation and Hatchery Management

  • Thoroughly clean and disinfect housing between flocks
  • Ensure hatching eggs come from tested, clean parent flocks
  • Clean and disinfect incubators and hatchers between batches

Water and Feed Management

  • Provide clean, uncontaminated drinking water at all times; sanitize drinkers regularly
  • Store feed securely to prevent contamination by rodents or wild birds
  • Avoid puddles and standing water near housing

Testing

Work with your state NPIP office or a licensed veterinarian to have your flock tested, especially before introducing new birds, selling or trading birds, or participating in poultry shows and exhibitions.

Vaccination (Outside the U.S.)

The Merck Veterinary Manual notes there are no federally licensed vaccines for fowl typhoid in the United States. In other countries — particularly in developing nations where the disease is still present in commercial flocks — vaccines made from a live attenuated rough strain of S. Gallinarum (the SG9R vaccine) are used.

However, vaccination comes with an important caveat: a 2023 study published in Frontiers in Veterinary Science (University of Pretoria, South Africa) identified a significant problem — in outbreaks in South Africa and Eswatini, whole genome comparison showed that field isolates causing disease were more closely related to the SG9R vaccine strains than to wild-type strains, raising concern about possible reversion to virulence of vaccine-derived bacteria. This finding highlights why vaccination programs for fowl typhoid must be carefully managed and monitored.

Emerging research is exploring probiotics as a complementary prevention tool. A 2023 study published in Animals (MDPI, University of Veterinary and Animal Sciences, Lahore) found that certain Limosilactobacillus fermentum strains isolated from healthy chicken intestines showed meaningful inhibitory activity against Salmonella Gallinarum in laboratory conditions — an early but promising step toward antibiotic-free prevention support.

Global Status: Where Is Fowl Typhoid Today?

Understanding the global picture helps explain why this disease remains a serious concern even in countries where it has been eradicated locally.

Fowl typhoid has been eradicated from commercial poultry in the U.S., Canada, the UK, Australia, Japan, and most of Western Europe through programs like the NPIP. However, it continues to cause major outbreaks in:

  • Latin America — Brazil has documented over 90 commercial flock outbreaks in official records in less than a decade; Mexico recorded an ongoing outbreak as recently as April 2024, according to the World Animal Health Information System (WAHIS)
  • Sub-Saharan Africa — significant economic losses in commercial and village flocks
  • South and Southeast Asia — widespread in Pakistan, India, Bangladesh, and surrounding regions
  • Middle East and North Africa — ongoing presence in commercial and backyard flocks

A 2024 PMC study noted that sporadic fowl typhoid outbreaks have also occurred in European countries — including Belgium, Bulgaria, France, Germany, Hungary, Italy, the Netherlands, Romania, and the UK — over recent decades, demonstrating that even in countries with strong control programs, the risk of reintroduction is real.

This global context matters for U.S. flock owners because imported birds or hatching eggs from unverified international sources represent a potential re-entry pathway for the disease.

Is Fowl Typhoid a Risk to Human Health?

Unlike many Salmonella strains that cause food poisoning in humans, Salmonella Gallinarum is highly host-specific to birds. The 2024 Antibiotics review confirms that it shows minimal zoonotic risk — meaning it very rarely, if ever, causes disease in humans.

However, this does not mean poultry keepers should be complacent. Any time you handle sick birds or their droppings, basic hygiene practices — washing hands thoroughly, avoiding touching your face, and keeping birds out of food preparation areas — are always appropriate.

When to Call Your Veterinarian — and Your State Veterinarian

Call a veterinarian immediately if you observe:

  • Multiple adult birds dying suddenly or within a short period of each other
  • Greenish or yellowish diarrhea spreading through the flock
  • Pale, anemic-looking combs and wattles alongside depression
  • A sudden severe drop in egg production
  • High early chick mortality, especially from purchased eggs or chicks

Contact your state veterinarian if:

  • Laboratory results confirm S. Gallinarum in your flock — this is legally required
  • You have reason to believe you may have purchased birds from an infected source
  • You are unsure about NPIP testing requirements before selling, exhibiting, or transporting birds

Fowl typhoid can move fast. Early reporting and rapid response — including quarantine — is the best protection for your flock, neighboring flocks, and the broader industry.

Summary Table

Topic Key Point
Cause Salmonella enterica serovar Gallinarum (SG)
Most At Risk Adult and growing chickens; also chicks from infected eggs
How It Spreads Egg transmission, fecal-oral, direct contact, carrier birds
Key Signs Pale comb, green-yellow diarrhea, sudden death, liver lesions
Diagnosis Bacterial culture + serotyping; WBPA blood test for screening
Treatment Generally NOT recommended (creates carriers); depopulation preferred
U.S. Status Eradicated from commercial flocks via NPIP; still reportable
Prevention NPIP-certified birds, biosecurity, flock testing, sanitation
Vaccine (U.S.) No federally licensed vaccine available in the United States

References and Resources

  1. Merck Veterinary Manual — “Fowl Typhoid.” Reviewed/Revised 2024. merckvetmanual.com
  2. Farhat, M., Khayi, S., Berrada, J., et al. (2024). “Salmonella enterica Serovar Gallinarum Biovars Pullorum and Gallinarum in Poultry: Review of Pathogenesis, Antibiotic Resistance, Diagnosis and Control in the Genomic Era.” Antibiotics, 13(1): 23. DOI: 10.3390/antibiotics13010023.
  3. Rodríguez, C., et al. (2023). “Genomic Characterization and Genetic Profiles of Salmonella Gallinarum Strains Isolated from Layers with Fowl Typhoid in Colombia.” Genes, 14(4): 823. DOI: 10.3390/genes14040823.
  4. Hendriksen, R.S., et al. (2023). “Salmonella gallinarum strains from outbreaks of fowl typhoid fever in Southern Africa closely related to SG9R vaccines.” Frontiers in Veterinary Science, 10: 1191497. DOI: 10.3389/fvets.2023.1191497.
  5. Alves, L.B.R., et al. (2024). “Salmonella Gallinarum mgtC mutant shows a delayed fowl typhoid progression in chicken.” Gene, 892: 147827. DOI: 10.1016/j.gene.2023.147827. PubMed: 37748627.
  6. PMC / Microbiology Society (2024). “Identification of Salmonella enterica biovars Gallinarum and Pullorum and their antibiotic resistance pattern in integrated crop-livestock farms and poultry meats.” PMC11652723.
  7. Mehmood, A., Nawaz, M., Rabbani, M., & Mushtaq, M.H. (2023). “In Vitro Characterization of Probiotic Potential of Limosilactobacillus fermentum against Salmonella Gallinarum Causing Fowl Typhoid.” Animals, 13(8): 1284. DOI: 10.3390/ani13081284. PMC10135235.
  8. Global S. Gallinarum Genome Dataset 1920–2024. PubMed 39375387 (2024). DOI via PubMed/NCBI.
  9. Clemson University NPIP — “About NPIP.” clemson.edu/public/lph/ahp/poultry-npip
  10. USDA-APHIS — National Poultry Improvement Plan (NPIP). aphis.usda.gov
  11. eXtension / USDA — “Fowl Typhoid in Poultry.” poultry.extension.org
  12. PoultryDVM — “Fowl Typhoid in Chickens: Signs, Treatment & Prevention.” poultrydvm.com
  13. Gast, R.K. & Porter, R.E. “Salmonella Infections.” In: Swayne, D.E., ed. Diseases of Poultry, 14th ed. Wiley-Blackwell; 2020: 719–753.

This article is for educational purposes only. Fowl typhoid is a federally reportable disease in the United States. Always consult a licensed veterinarian and notify your state veterinarian if you suspect infection in your flock.