Fowl Typhoid in Chickens: Salmonella Gallinarum Infection and Sudden Losses

Fowl typhoid is a serious bacterial disease of chickens caused by Salmonella enterica serovar Gallinarum biovar Gallinarum, often shortened to Salmonella Gallinarum. It is a poultry-adapted salmonella, which means it is especially suited to infecting birds rather than many different animal species. The disease can move fast through a flock and may cause acute illness, sudden losses, or a more drawn-out course with weakness and poor production.

This infection is most often recognized in growing and adult birds, including laying hens, although younger birds can also become sick. Birds may look depressed, stop eating, develop diarrhea, become dehydrated, and die with little warning. On necropsy, your vet or diagnostic lab may find an enlarged, fragile liver, enlarged spleen and kidneys, and other signs of septicemia.

Fowl typhoid is now uncommon in U.S. domestic poultry because of long-standing control efforts through the National Poultry Improvement Plan, but it remains important worldwide. That matters for backyard flocks too. A single infected bird, contaminated hatching egg, or lapse in biosecurity can put the rest of the flock at risk.

Fowl typhoid is caused by Salmonella Gallinarum, a gram-negative, nonmotile bacterium that is highly adapted to chickens and turkeys. Unlike many other salmonella types, this one is mainly a bird disease. It can be transmitted vertically through eggs and horizontally through feces, secretions, contaminated litter, feeders, waterers, crates, boots, and other equipment.

Infected or carrier birds are a major source of spread. New flock additions, birds returning from swaps or shows, and hatching eggs from unknown health programs can all increase risk. Rodents, poor sanitation, and multi-age housing can make control harder. International sources also note that red mites may help the organism persist in poultry houses.

Stress can make outbreaks worse. Overcrowding, transport, heat, poor ventilation, and concurrent disease can lower resistance and allow faster flock spread. In laying hens, the disease may be especially severe and can lead to sudden drops in production along with illness and death.

Diagnosis starts with the flock story. Your vet will ask about recent deaths, age groups affected, new bird introductions, hatchery sources, travel to swaps or shows, and whether eggs or chicks came from a monitored breeding program. A physical exam of live birds may show dehydration, weakness, diarrhea, and pallor, but these findings do not confirm fowl typhoid on their own.

A necropsy is often the fastest next step when birds die suddenly. Typical findings can include an enlarged, friable, sometimes bile-stained liver, enlarged spleen and kidneys, enteritis, and lesions in other organs. In young birds, lesions can overlap with pullorum disease, so appearance alone is not enough.

Definitive diagnosis requires laboratory isolation and identification of the organism, often with serotyping. Your vet may submit whole birds or tissue samples to a veterinary diagnostic laboratory for culture and related testing. Serologic screening can support flock investigation, but confirmation depends on identifying S. Gallinarum. In the U.S., your vet may also coordinate with state animal health officials or NPIP-related testing pathways when flock control decisions are needed.

Prevention starts with flock biosecurity. Keep a closed flock when possible, and quarantine all new birds before they join the group. Avoid sharing crates, feeders, waterers, and show equipment unless they have been thoroughly cleaned and disinfected. Buy chicks, started pullets, and hatching eggs from reputable sources that follow recognized health monitoring programs, including NPIP participation when relevant.

Good sanitation lowers risk. Clean manure and wet litter regularly, keep feed protected from rodents and wild birds, and disinfect high-contact surfaces between groups. If you have a sudden unexplained death, remove the body promptly and contact your vet before losses spread. In some settings outside the United States, live or inactivated vaccines are used, but Merck notes there are no federally licensed fowl typhoid vaccines in the U.S. as of 2026.

Long-term prevention also means avoiding silent spread. Do not move birds on or off the property during an active illness investigation. Be cautious with swaps, exhibitions, and mixed-age housing. If your flock has had a confirmed salmonella problem, your vet can help you decide whether testing, culling, extended downtime, or a full cleanup-and-restart plan is the safest path for future birds.