Pullorum Disease in Chickens: White Diarrhea in Chicks and Flock Risk

Pullorum disease is a contagious bacterial infection of poultry caused by Salmonella enterica serovar Gallinarum biovar Pullorum, often shortened to Salmonella Pullorum. It was historically called bacillary white diarrhea because affected chicks often pass chalky white droppings that stick around the vent. The disease is especially dangerous in very young chicks and poults, where it can cause heavy losses early in life.

In the United States, pullorum disease has been largely eliminated from commercial breeding flocks through the National Poultry Improvement Plan (NPIP). That said, it can still appear in backyard, hobby, exhibition, or mixed-species flocks. This matters because apparently healthy adult birds can sometimes carry the organism and pass it to eggs or other birds.

For pet parents, the biggest concern is not only the sick chick in front of you. It is the whole-flock risk. A few weak chicks with white diarrhea can signal a problem that affects hatchability, chick survival, and the long-term health status of the flock. Early veterinary guidance helps you protect both current birds and future hatchlings.

Pullorum disease is caused by Salmonella Pullorum, a poultry-adapted bacterium. One of the most important routes of spread is vertical transmission, meaning an infected hen can pass the organism into the egg. Chicks can also become infected from contaminated hatchers, brooders, feeders, waterers, litter, or contact with infected birds and their droppings.

This disease is especially concerning in breeding and hatching settings because a single carrier bird can affect many eggs or chicks. Infection from the egg or hatchery environment often leads to illness and death very early in life. Adult birds may look normal, which makes the flock risk harder to spot without testing.

Backyard flocks are at higher risk when birds are added from swaps, auctions, informal breeders, or mixed sources without health documentation. Shared equipment, poor sanitation, and mixing chickens with other susceptible birds such as game birds or some ornamental species can also increase spread. Your vet can help you sort out whether the problem is likely coming from the hatch source, the environment, or carrier birds already in the flock.

Diagnosis starts with the story: chick age, hatch source, death losses, and whether there is white pasted diarrhea or poor hatchability. Your vet may examine sick birds and, if a chick has died, recommend a necropsy. Pullorum disease can look similar to other causes of chick diarrhea and weakness, so appearance alone is not enough for a firm diagnosis.

Screening in live birds may include serologic blood testing, which is often used for surveillance or exhibition requirements. However, screening tests are not perfect. According to veterinary references, definitive diagnosis is made by isolation and identification of the organism, usually through a veterinary diagnostic laboratory using tissues from dead birds, eggs, or other samples.

In practical terms, many backyard flocks need a combination approach: isolate affected birds, submit a fresh dead chick for necropsy if possible, and discuss flock testing with your vet or state poultry health officials. Because pullorum disease has regulatory and flock-certification implications in some settings, your vet may also coordinate with a state diagnostic lab or poultry program.

Prevention starts with source control. Buy chicks, hatching eggs, and breeding birds from reputable suppliers that participate in recognized health programs such as NPIP. This does not remove every risk, but it greatly lowers the chance of bringing pullorum disease into your flock. Avoid impulse additions from swaps, auctions, or unknown backyard sources unless you can verify testing history.

Good biosecurity also matters. Quarantine new birds, keep brooders and incubators clean, and do not share feeders, waterers, crates, or show equipment without thorough cleaning and disinfection. If you hatch your own chicks, pay close attention to egg hygiene, incubator sanitation, and separating age groups so older birds do not expose fragile hatchlings.

If you keep exhibition or breeding birds, ask your vet whether routine pullorum testing is appropriate for your flock and local rules. Fast action after unexplained chick deaths can prevent bigger losses. In many cases, the most effective prevention plan is a combination of tested source birds, strict quarantine, careful hatch sanitation, and early veterinary involvement when something looks off.