Veterinary Services 

Centers for Epidemiology and Animal Health December 2003 

_________________________________________________________________________________________________________________________ 

Salmonella and 

Campylobacter on U.S. Dairy 

Operations 

Background 

In 2002, there were approximately 16,500 

laboratory-diagnosed cases of bacterial foodborne 

illness in humans in the United States.1 Of these 

cases, 67 percent were caused by species of 

Salmonella and Campylobacter. Both of these 

pathogens cause fever, abdominal cramping, and 

diarrhea in humans. Severe cases can result in 

systemic infections and even death. 

 The percentage of culled dairy cows shedding 

Salmonella and Campylobacter is higher than in 

dairy cows in normal production. Culled dairy cows 

represent a substantial portion of the nation’s 

ground beef and may serve as a potential source of 

foodborne salmonellosis and campylobacteriosis 

when meat is contaminated with fecal material at 

slaughter.2 3

Salmonella on U.S. Dairy Operations 

Clinical signs of salmonellosis in cattle include 

fever, diarrhea, anorexia, and decreased milk 

production. Infection can range from subclinical to 

endotoxemia and death.4 Cows can shed 

Salmonella in their feces due to stress incurred 

during transportation, lactation, and calving, without 

showing clinical signs typically associated with 

infection.4 

 Although over 2,000 serotypes of Salmonella

have been identified, most laboratory-confirmed 

Salmonella infections in cattle are due to a small 

number of serotypes. Recently, a drug-resistant 

form of Salmonella serotype (Newport) has 

emerged.5 These multidrug-resistant isolates have 

caused disease in humans, adult cattle, and less 

commonly in calves, and are of concern to both 

veterinary and public health officials. 

The National Animal Health Monitoring 

System’s (NAHMS) Dairy ’96 study determined that 

27.5 percent of dairy operations and 66.7 percent 

of livestock markets studied had at least one cow 

shedding Salmonella.

 2 Fecal shedding was higher 

in dairy cows designated for culling within 7 days 

and in market dairy cattle than in cows in normal 

production. 

 In 2002, the USDA’s National Animal Health 

Monitoring System (NAHMS) conducted Dairy 

2002, NAHMS’ third national study of U.S. Dairy 

operations. During Dairy 2002, fecal samples were 

collected via rectal retrieval from approximately five 

operations in each of the 21 States* participating in 

the study. On each operation, fecal samples were 

collected from approximately 40 cows. From March 

27 through September 25, 2002, a total of 3,669 

samples were collected on 96 operations and 

cultured for Salmonella. 

The percentage of cows where Salmonella was 

recovered from feces increased from 5.4 percent in 

the Dairy ’96 study to 7.3 percent in the Dairy 2002 

study. This increase was statistically significant. 

The overall percentage of operations with one or 

more Salmonella-positive cows also increased from 

27.5 percent in Dairy ’96 to 31.3 percent in Dairy 

2002, although this increase was not statistically 

significant. Figure 1 shows the regional breakout of 

operations with at least one positive Salmonella

sample. 

_______________________ 

*Regions/States: 

West: California, Colorado, Idaho, New Mexico, Texas Washington 

Midwest: Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, 

Wisconsin 

Northeast: New York, Pennsylvania, Vermont 

Southeast: Florida, Kentucky, Tennessee, Virginia 
 

0

20

40

60

80

West Midwest Northeast Southeast All 

31.3

42.9

25.6

6.7

50.0

Percent

Region

Figure 1. Percent of Operations in Dairy 2002 With at

Least One Positive Salmonella Sample, by Region

(n=28) (n=39) (n=15) (n=14) (n=96)

Overall, 294 Salmonella isolates were isolated 

from the 269 Salmonella-positive samples collected 

during the Dairy 2002 study. The five most common 

serotypes of Salmonella recovered are summarized 

in Table 1. In addition, S. Newport represented 2.7 

percent of the Salmonella isolates recovered, and 

seven of the eight S. Newport isolates were 

multidrug resistant. 

Table 1. Percent of Isolates for the Five Most Common 

Salmonella Serotypes Isolated from Cattle Feces Collected 

During Dairy 2002:

Salmonella serotype Percent Isolates 

Meleagridis 24.1 

Montevideo 11.9 

Typhimurium 9.9 

Kentucky 9.5 

Agona 7.5 

 

Campylobacter on U.S. Dairy Operations 

 Although Campylobacter species can be 

considered commensal organisms or normal flora 

in livestock, they also may produce diarrhea in 

neonatal calves, and may cause abortion, infertility, 

and early embryonic death in adult cattle.6 7 

Foodborne transmission of Campylobacter can 

occur through fecal contamination of carcasses at 

slaughter and also through fecal contamination of 

milk or water.8 9 

 In Dairy ’96, it was determined by a multiplex 

polymerase chain reaction assay that 80.6 percent 

and 19.4 percent of dairy operations were positive 

for Campylobacter jejuni and Campylobacter coli,

respectively.7 Approximately 38 percent of dairy 

cows had fecal samples positive for C. jejuni and 

1.8 percent were positive for C. coli. 

 Of the 3,669 samples tested for Salmonella in 

the Dairy 2002 study, 1,450 also were tested for

Campylobacter. Results from Dairy 2002 showed 

that 51.4 percent of cows were shedding 

Campylobacter species, as determined through 

fecal cultures. Overall, 97.9 percent of operations 

sampled had at least one cow shedding 

Campylobacter in their feces. 

Conclusions 

The percentage of cows shedding Salmonella

and the percentage of dairy herds with at least one 

cow shedding Salmonella increased slightly 

between Dairy ’96 and Dairy 2002: 5.4 percent to 

7.3 percent of cows, respectively; and 27.5 percent 

to 31.3 percent of operations, respectively. 

Salmonella Newport, a serotype of Salmonella of 

particular interest at this time, represented 2.7 

percent of isolates. Campylobacter was isolated 

from approximately one of two (51.4 percent) cows 

sampled and was found in at least one cow on 97.9 

percent of dairies sampled. Continued efforts by 

dairy producers to decrease the spread of 

Salmonella and Campylobacter will help limit cattle 

morbidity and mortality, and reduce the zoonotic 

spread of these organisms. 

References 

1. CDC. Preliminary FoodNet data on the incidence of 

foodborne illnesses – selected sites, United States, 

2002. Morb Mortal Weekly Rept 2003; 52:340-343. 

2. Kabagambe EK, Wells SJ, Garber LP, et al. Risk 

factors for fecal shedding of Salmonella in 91 U.S. 

dairy herds in 1996. Prev Vet Med 2000; 43:177-

194. 

3. Troutt HF, Galland JC, Osburn BI, et al. Prevalence 

of Salmonella spp. in cull (market) dairy cows at 

slaughter. J Am Vet Med Assoc 2001; 219:1212-

1215. 

4. House JK, Smith BP. Current strategies for 

managing Salmonella infections in cattle. Food An 

Pract 1998; 93:756-764. 

5. USDA, APHIS, Centers for Epidemiology and Animal 

Health. What veterinarians and producers should 
know about multidrug-resistant Salmonella Newport. 

Fort Collins, CO, 2002. 

6. Smith BP. Large animal internal medicine. Mosby, 

St. Louis, MO, 2002; 353, 967-968. 

7. Wesley IV, Wells SJ, Harmon KM, et al. Fecal 

shedding of Campylobacter and Arcobacter spp. in 

dairy cattle. Appl Environ Microbiol 2000; 66:1994-

2000. 

8. CDC. Outbreak of Campylobacter jejuni infections 

associated with drinking unpasteurized milk 

procured through a cow-leasing program – 

Wisconsin, 2001. Morb Mortal Weekly Rept 2002; 

51:548-549. 

9. CDC. Surveillance for Waterhouse-disease 

outbreaks – United States, 1999-2000. Morb Mortal 

Weekly Rept 2002; 51(SS08):1-28. 

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 

E-mail: NAHMSweb@aphis.usda.gov 

www.aphis.usda.gov/vs/ceah/cahm

#N401.1203 

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