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 

diseases:

• Pullorum—An egg-transmitted disease of poultry, 

caused by Salmonella pullorum, that kills a high 

proportion (60–80 percent) of baby poultry

• Fowl typhoid—An egg-transmitted disease of 

poultry, caused by Salmonella gallinarum, that 

may result in significant mortality in both baby 

poultry and adult birds

• Avian mycoplasmas—The species of Mycoplasma that are most pathogenic to poultry are the 

ones covered by the testing program in the NPIP: 

Mycoplasma gallisepticum (MG), Mycoplasma 

synoviae (MS), or Mycoplasma meleagridis (MM)

• Salmonella enterica*—An egg-transmitted 

disease of poultry, caused by the organism of the 

same name, that may also have human health 

implications through consumption of contaminated 

table eggs

• Avian influenza—A worldwide viral infection of 

several species of poultry

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 diseased hens are infected at 

conception inside the egg.

*Taxonomists have recently changed the 

Latin names for several bacteria in the 

genus Salmonella. Most sources now 

call S. enteritidis Salmonella enterica subspecies enterica, serovar enteritidis. 

NPIP certificates can be revised to show 

the changed name after the correction is 

made to the NPIP sections of the Code of 

Federal Regulations. The NPIP General 

Conference Committee and Technical 

Committee will consider the name change 

at the next biennial conference.

 Pullorum disease will also affect turkeys, ducks, 

guinea fowl, pheasants, sparrows, quail, bittern, 

geese, pigeons, doves, parakeets, and canaries. 

The causative organism, Salmonella pullorum, rarely 

affects mammals. 

 Once called bacillary white diarrhea of chicks, 

pullorum has been a devastating disease of poultry 

for more than 50 years. It causes heavy losses in 

chicks and poultry and reduces the productivity 

of adult birds. Young birds die during their first 

3 weeks. Losses may be as high as 80–90 percent of 

the brood. Death from pullorum rarely occurs after 4 

weeks of age. Infected adult birds normally show 

no outward evidence of infection, but they are 

disease carriers for life.

 The infection may spread by breathing contaminated dust or coming into contact with down from 

infected poultry or with other material in the incubator, 

shipping box, brooder, or pen that has been touched 

by infected birds. Infected feces in litter and feed or 

water can transmit the disease to other brood-mates. 

One chick might infect an entire hatch of birds. If 

young birds have other diseases, pullorum tends to 

spread faster.

 Carrier hens lay infected eggs, and the hatchlings are infected. Hens can be infected by eating 

contaminated feed, infected eggs, or manure from 

other infected chickens. 

 Blood-testing adult breeding birds, biosecurity, 

and sanitation have all but eliminated the disease in 

the United States. Pullorum–typhoid testing is available through State agencies as a free service or at 

a nominal charge. Individual poultry raisers may be 

certified by these State agencies as testing agents in 

some States.

 Pullorum can be controlled and eradicated by 

eliminating infected carrier birds and thus breaking 

the disease cycle. Blood-testing potential breeding animals and culling infected birds are the steps 

needed to eliminate the eggborne disease. Breeders 

that have tested negative produce noninfected eggs 

and thus noninfected chicks.

 The official blood tests of the NPIP for pullorum–

typhoid are the rapid whole-blood plate agglutination 

test, the rapid serum plate test, the standard tube 

agglutination test, and the microagglutination test. 

These tests use whole blood or serum of infected 

birds which contain antibodies that will clump (stick together, agglutinate) when mixed with stained pullorum 

organisms.

MG, MS, and MM are the species of Mycoplasma that are pathogenic to poultry.

 MG is commonly called chronic respiratory 

disease in chickens and infectious sinusitis in turkeys. 

Producers with MG-affected flocks suffer economic 

losses from downgraded carcasses, lowered eggproduction efficiency, and increased medication costs. 

MS can become systemic and cause acute synovitis 

of chickens and turkeys. MM’s primary lesion is airsacculitis in baby turkeys.

Avian influenza is a worldwide viral infection of 

poultry. An influenza virus has the ability to mutate, 

or change its genetic character, so that it can infect a 

host animal in one of several ways. The host responses from influenza infection can range from no 

apparent signs to mild and moderate illness to death. 

Because of the different symptoms of influenza, three 

levels of host disease are described: nonpathogenic, 

low-pathogenicity, and high-pathogenicity avian 

influenza.

Figure 1—Results of the rapid whole-blood 

plate agglutination test for pullorum are 

positive (top left), suspect (top right), and 

negative (bottom). (Photo by Gene Lambert 

of Paradigm Media; reproduced by permission.)
The agar gel immunodiffusion test is the official 

test for avian influenza under the NPIP. The test must 

be conducted only in laboratories authorized under 

the NPIP, and tissues from all suspects are subtyped 

at the National Veterinary Services Laboratories, 

Ames, IA.

 Fowl typhoid is a salmonella infection similar to 

pullorum but caused by Salmonella gallinarum. Both 

diseases elicit common antigenic reactions. The 

same blood test works for both diseases. Since 1954, 

breeders are considered negative for both diseases 

on the results of the same test.

Salmonella enterica-infected chickens often 

display no symptoms at all. But because this disease 

is egg-transmitted, like pullorum, it can be passed 

in the intact egg. Because Salmonella enterica is a 

human pathogen, it must be eliminated from breeding 

chickens.

For more information, visit

<http://www.aphis.usda.gov/vs/npip>.

The U.S. Department of Agriculture (USDA) 

prohibits discrimination in all its programs 

and activities on the basis of race, color, 

national origin, age, disability, and where 

applicable, sex, marital status, familial status, 

parental status, religion, sexual orientation, 

genetic information, political beliefs, reprisal, 

or because all or part of an individual’s 

income is derived from any public assistance 

program. (Not all prohibited bases apply to 

all programs.) Persons with disabilities who 

require alternative means for communication 

of program information (Braille, large print, 

audiotape, etc.) should contact USDA’s 

TARGET Center at (202) 720–2600 (voice and 

TDD). To file a complaint of discrimination, 

write to USDA, Director, Office of Civil Rights, 

1400 Independence Avenue, S.W., Washington, 

D.C. 20250–9410, or call (800) 795–3272 (voice) 

or (202) 720–6382 (TDD). USDA is an equal 

opportunity provider and employer.

Issued November 2001

Slightly revised January 2006

National Poultry Improvement Plan1498 Klondike Road, Suite 101Conyers, GA 30094Phone: (770) 922–3496Fax: (770) 922–3498

United States Department of Agriculture

Animal and Plant Health Inspection Service

Program Aid No. 1708

Helping You, 

the Poultry Breed-

er, Prevent Dis-

ease