Objective—To describe the frequency and distribution
of Escherichia coli O157:H7 in the feces and environment
of cow-calf herds housed on pasture.
Sample Population—Fecal and water samples for 10
cow-calf farms in Kansas.
Procedure—Fecal and water samples were obtained
monthly throughout a 1-year period (3,152 fecal samples
from 2,058 cattle; 199 water samples).
Escherichia coli O157:H7 in fecal and water samples
was determined, using microbial culture.
Results—Escherichia coli O157:H7 was detected in
40 of 3,152 (1.3%) fecal samples, and 40 of 2,058
(1.9%) cattle had ≥ 1 sample with E coli. Fecal shedding
by specific cattle was transient; none of the cattle
had E coli in more than 1 sample. Significant differences
were not detected in overall prevalence
among farms. However, significant differences were
detected in prevalence among sample collection
dates. Escherichia coli O157:H7 was detected in 3 of
199 (1.5%) water samples.
Conclusions and Clinical Relevance—Implementing
control strategies for E coli O157:H7 at all
levels of the cattle industry will decrease the risk of
this organism entering the human food chain.
Devising effective on-farm strategies to control E coli
O157:H7 in cow-calf herds will require an understanding
of the epidemiologic characteristics of this
pathogen. (Am J Vet Res 2000;61:1375–1379)
Objective—To determine the diversity of Salmonella
serotypes isolated from a large population of cull
(market) dairy cows at slaughter.
Sample Population—Salmonella organisms isolated
from the cecal-colon contents of 5,087 market dairy
Procedure—During winter and summer 1996, cecalcolon
contents of cull dairy cows at slaughter were
obtained from 5 US slaughter establishments.
Specimens were subjected to microbiologic culturing
for Salmonella spp at 1 laboratory. Identified isolates
were compared with Salmonella isolation lists published
by the Centers for Disease Control and
Prevention (CDC) and the National Veterinary Services
Laboratory (NVSL) for approximately the same period.
The Simpson diversity index was used to calculate
the likelihood that Salmonella isolates selected randomly
by establishment were different.
Results—Of 58 Salmonella serotypes identified,
Salmonella ser. Montevideo was the most prevalent. Two
of the top 10 CDC serotypes identified from humans in
1996, Salmonella ser. Typhimurium and S Montevideo,
appeared on our top 10 list; 8 of the top 10 were found
on NVSL listings. Thirty-one of 59 S Typhimurium isolates
were identified as DT104 and found at a west slaughter
establishment, 30 during the winter and 1 during the
summer. The greatest diversity of serotypes was at a
southeast establishment during the summer; the least
diversity was at a central establishment in the winter.
Conclusions and Clinical Relevance—58 Salmonella
serotypes were isolated from market dairy cows at
slaughter and could pose a threat for food-borne illness.
Salmonella Montevideo was the most frequently
isolated serotype and may contribute substantially
to salmonellosis in dairy cattle. (J Am Vet
Med Assoc 2001;219:1216–1220)
Objective—To determine the prevalence of
Salmonella spp in the cecal-colon contents of cull
(market) dairy cows at slaughter because of potential
public health ramifications.
Sample Population—Cecal-colon contents collected
from 5,087 cull (market) dairy cows at slaughter at 5
slaughter establishments across the United States.
Procedure—During 2 periods of the year, winter
(January and February) and summer (July through
September), 5 cull (market) cow slaughter establishments
in the United States—west (WE), southeast
(SEE), central (CE), north central (NCE), and south central
(SCE)—establishments were visited, and cecalcolon
contents of cull dairy cows were obtained at the
time of slaughter. Samples were examined by microbiologic
culture at a single laboratory for Salmonella spp.
Results—Salmonella spp were detected in 23.1% of
cecal-colon content samples from cull dairy cows
across the 5 slaughter establishments. The highest
site prevalence (54.5%) was detected at the WE during
the summer period, whereas the lowest was
found at the CE during the summer (4.3%) and at the
NCE during the winter (4.5%). Considerable variation
in the daily prevalence of Salmonella spp was found,
particularly at the WE and the SCE. Salmonella spp
were isolated from 93% of cecal-colon contents collected
on a summer day at the WE.
Conclusions and Clinical Relevance—Results
strongly suggest that there is a high prevalence of
Salmonella spp in cull dairy cows at slaughter, which
could burden Hazard Analysis Critical Control Point
programs implemented in slaughter establishments.
Procedures to reduce Salmonella load at the dairy
farm and during transport to slaughter could reduce
the risk of spread during the slaughter process. (J
Am Vet Med Assoc 2001;219:1212–1215)