United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Veterinary Services 

Centers for Epidemiology and Animal Health June 2012 

_________________________________________________________________________________________________________________________ 

Respiratory Disease on BreederChicken Farms in the United 

States 

Breeder-chicken farms consist of primary breeders 

whose progeny are breeding birds, and multipliers 

whose progeny are broilers and table-egg layers. 

Breeder farms provide the genetics for the poultry 

industry, and the birds on these farms are very valuable. 

Therefore, it is crucial to prevent disease introduction 

that could threaten the farms’ genetic stock. 

The USDA’s National Animal Health Monitoring 

System (NAHMS) conducted a study of breeder-chicken 

farms in 2010. A total of 482 breeder farms located in 

the Central and East regions of the United States 

participated in the study (see map). The study 

questionnaire addressed potential risk factors for 

respiratory disease relating to farm surroundings, 

farm/house characteristics, human traffic, birds and 

other animals on the farm, and bird/egg movement and 

transport. 

Occurrence of respiratory disease 

Breeder farms placed hens in the laying house at 

20.9 weeks of age and removed them at 64.1 weeks of 

age, on average. Breeder farms reported the 

occurrence of specific diseases in the last completed 

flock, including the following respiratory diseases: 

Mycoplasma synoviae (MS), Mycoplasma gallisepticum

(MG), infectious laryngotracheitis (ILT), Newcastle 

disease, infectious bronchitis, infectious coryza, and 

avian influenza. Respiratory disease occurred rarely (4.6 

percent of last completed flocks). No breeder farms 

reported MG, Newcastle disease, infectious coryza, or 

avian influenza in their last completed flock. MS, ILT, 

and infectious bronchitis occurred in the last completed 

flock on 2.0, 1.8, and 0.9 percent of breeder farms, 

respectively (table 1). ILT did not occur in breeder flocks 

in the Central region (table 1) or in primary breeder 

flocks (table 2). Table-egg type breeder farms had no 

occurrences of MS or ILT in the last completed flock 

(table 3). 

Table 1. Percentage of farms that had the following 

respiratory diseases in the last completed flock, by 

region 

Percent Farms 

Region 

Respiratory disease Central East 

All 

farms 

Mycoplasma synoviae

(MS) 1.6 2.1 2.0 

Infectious laryngotracheitis 

(ILT) 0.0 2.4 1.8 

Infectious bronchitis 1.1 0.8 0.9 

Any 2.7 5.2 4.6 

Table 2. Percentage of farms that had the following 

respiratory diseases in the last completed flock, by 

farm type 

Percent Farms 

 Farm Type 

Respiratory disease 

Primary 

breeder Multiplier 

Mycoplasma 

synoviae (MS) 3.8 1.8 

Infectious 

laryngotracheitis (ILT) 0.0 2.1 

Infectious bronchitis 2.6 0.7 

Any 6.4 4.4 

F L

N M

D E M D

T X O K

K S

N E

S D

N D

M T

W Y

C O

U T

ID

A Z

N V

W A

C A

O R

K Y

M E

N Y

P A

M I

V T N H

M A

R I C T

V A

W V

O H IN

IL

N C

T N

S C

M S A L

A R

L A

M O

IA

M N

W I

N J

G A

Poultry 2010 Regions

Regions

East

Central

Technical Brief
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Table 3. Percentage of farms that had the following 

respiratory diseases in the last completed flock, by 

breeder farm type 

Percent Farms 

 Breeder Farm Type 

Respiratory disease Broiler Table egg

Mycoplasma synoviae (MS) 2.0 0.0 

Infectious laryngotracheitis (ILT) 1.9 0.0 

Infectious bronchitis 0.9 2.5 

Any 4.7 2.5 

MS was the only respiratory disease problem in the 

last completed flock that any breeder farms ranked as 

moderate or severe (table 4). Slight problems with ILT 

and infectious bronchitis were reported. 

Table 4. Percentage of breeder farms by severity of 

respiratory disease problems in the last completed 

flock 

Percent Breeder Farms 

 Severity 

Respiratory 

disease Severe Moderate Slight None 

Mycoplasma 

synoviae (MS) 0.7 0.5 0.8 98.0 

Infectious 

laryngotracheitis 

(ILT) 

0.0 0.0 1.8 98.2 

Infectious 

bronchitis 0.0 0.0 0.9 99.1 

Risk factors associated with respiratory disease

Figure 1 and table 5 show factors related to 

area/farm location that were associated with the 

occurrence of respiratory disease in the last completed 

flock. Each factor was evaluated individually against the 

outcome of respiratory disease. Results are presented 

as odds ratios. The odds ratio is the likelihood of having 

respiratory disease for farms with the factor compared 

with farms without the factor. A higher percentage of 

farms located in counties with a high density of birds 

(poultry) and poultry farms had respiratory disease in the 

last completed flock compared with farms in counties 

with lower densities of poultry or farms (OR=11.6 and 

8.1 respectively). Additionally, a higher percentage of 

farms within 1 mile of another commercial poultry 

operation had respiratory disease than farms that were 

not in such close proximity to another commercial 

operation (OR=15.3). A higher density of poultry could 

potentially increase the pathogen load as well as 

opportunities for exposure to pathogens. 

Table 5. Percentage of farms with respiratory 

disease in last completed flock, by area/location 

factors 

 Percent Farms 

Factor 

With 

factor 

Pct. 

positive

Odds 

ratio P-value

Poultry density 

2,000 birds or 

more/sq mi 

Yes 4.0 11.6 0.02 

No 0.4 referent 

Poultry density 

0.25 or more 

poultry farms/ 

sq mi 

Yes 6.5 8.1 0.04 

No 0.9 referent 

Another 

commercial 

poultry operation 

within 1 mi 

Yes 7.6 15.3 0.003 

No 0.5 referent 

0

5

10

No

Yes

Poultry density

2,000 birds or 

more/sq mi

Poultry density

0.25 or more

poultry farms/

sq mi

Another

commercial

poultry operation

within 1 mi

Factor

Percent

Figure 1. Percentage of farms with respiratory disease 

in last completed flock, by area/location factors 

With factor

4.0

0.4

6.5

0.9

7.6

0.5
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture 

Biosecurity practices also impact respiratory 

occurrence on breeder farms. Spraying tires of feeddelivery vehicles was associated with a reduced risk of 

respiratory disease, while allowing the feed deliverer to 

enter the poultry house, using catch crews that catch for 

other companies, and using buggies to load egg flats 

onto trucks that were used on other farms were all 

associated with an increased risk (table 6, figure 2). 

Although nearly all farms that used buggies on different 

farms cleaned and disinfected the buggies between 

farms (97.6 percent), it may be difficult to thoroughly 

remove all contamination on buggies, particularly on the 

wheels. 

Table 6. Percentage of farms with respiratory 

disease in last completed flock, by biosecurity 

characteristics 

Percent Farms 

Characteristic 

Character

-istic 

Pct. 

positive OR P 

Spray tires of feed 

delivery vehicle 

before entering 

farm 

Yes 0.6 referent 

No 6.9 11.3 0.007 

Feed deliverer 

entered poultry 

houses in 

previous 12 

months 

Yes 18.7 16.4 0.007 

No 1.4 referent 

Catch crews catch 

for other 

companies 

Yes 5.2 7.9 0.01 

No 0.7 referent 

Buggies to load 

egg flats onto 

truck used on 

other farms 

Yes 5.3 4.4 0.03 

No 1.3 referent 

Summary 

Movements of people and vehicles were the most 

important factors related to occurrence of respiratory 

disease on poultry breeder farms. Breeder farms located 

in poultry-dense areas need to be especially vigilant 

about biosecurity measures to prevent introduction of 

respiratory diseases to their farms. 

______________________________ 

For more information, contact: 

USDA–APHIS–VS–CEAH 

NRRC Building B, M.S. 2E7 

2150 Centre Avenue 

Fort Collins, CO 80526-8117 

970.494.7000 

http://nahms.aphis.usda.gov

#654.0612 

___________________________________ 

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provider and employer. 

0

5

10

15

20

No

Yes

Spray tires on

feed delivery

vehicle

Feed

deliverer

entered poultry 

houses

Catch crews

catch for

other

companies

Characteristic

Percent

Figure 2. Percentage of farms with respiratory disease 

in last completed flock, by biosecurity characteristics 

Characteristic

0.6

6.9

18.7

1.4

5.2

0.7

5.3

1.3

Buggies to

load egg

flats onto

truck used on

other farms