The National Poultry Improvement Plan (NPIP) was started in the early 1930s to coordinate State programs aimed at eliminating pullorum from commercial poultry. In those days, many poultry breeders served the needs of thousands of small flock owners. Today, there are only a very few breeders of commercial poultry to serve the commercial poultry industry, which produces billions of chickens and millions of turkeys annually.

Today, the NPIP concerns itself with certifying that flocks are free of the following disease:

• Pullorum
• Fowl typhoid
• Avian mycoplasmas
• Salmonella enterica
• Avian influenza

Pullorum disease, discovered in 1899, is a worldwide disease of chickens. The main reservoirs of infection are the egg-producing organs of the infected hen. chicks from disease hens are infected at conception inside the egg.

Pullorum disease will also affect turkeys, guinea fowl, pheasants, sparrows, quail, bittern, geese, pigeons, doves, parakeets, and canaries. The causative organism, Salmonella pullorum, rarely affects mammals.