Agriculture Reference
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potential sources of pathogen and relevant risk factors for contamination of produce
(Chase - Topping and others 2007 ).
The incidence data listed in Table 1.3 are from selected recent studies; the data
refl ect the dynamic nature of the incidence associated with different animal hosts,
spatial and temporal differences, and a variety of different methods. In a recent review
by Hussein and Bollinger, 39 reported studies of the incidence of E. coli O157:H7 in
thousands of cattle fecal samples from feedlots, pasture/range, and entering slaughter
ranged from 0.2 to 28%, depending upon the study and the cattle feeding or produc-
tion process (Hussein and Bollinger 2005). A previous review of some of the same
studies involving animals in Asia, Australia, Europe, and North America (sampling
periods between 1991-1999) reported incidence in fecal samples in the range of 0.1
to 62% (Duffy 2003). Indeed, the common occurrence of E. coli O157:H7 in cattle is
consistent with numerous outbreaks of E. coli O157:H7 occurring as a result of direct
human contact with animals, feces, or manures at fairs, farms, and other public settings
(Duffy 2003; Durso and others 2005; Keen and others 2006, 2007). Similar studies
of sheep in the U.K., U.S., and Spain, representing thousands of samples, reported
an incidence of E. coli O157 that ranged from 0.7 to 7.3%, and for domestic pigs
incidence ranged from 0.3 to 8.9% (Table 1.3).
In multiple studies of cattle feedlots and ranches, strains of E. coli O157:H7 per-
sisted for up to 24 months at individual farms, and strains indistinguishable by molecu-
lar typing methods were isolated from farms separated by up to 50 km (Rice and others
1999; LeJeune and others 2004; Wetzel and LeJeune 2006). Indeed, a link between
livestock and human illness with E. coli O157:H7 and other STEC has been supported
by a direct correlation reported between the density of livestock and amount of
reported illness in a region of Ontario, Canada (Michel and others 1999).
Salmonella enterica
Strains of S. enterica were isolated from 1.4 to 9% of beef cow fecal samples
(Australia, U.S., U.K.) reported in four studies (Table 1.3). In a recent study of 7,680
animal and environmental samples from a single U.S. dairy, 13-72% of the cattle
samples (depending upon period of testing), and
50% of air, soil, water, insect, and
bird feces samples yielded S. enterica (Pangloli and others 2008). Similarly, high
incidences of S. enterica in pigs were reported in a U.K. study (23.4%), in poultry
fl ocks (10.5 to 13%) in U.S. and Belgium studies, and in poultry production environ-
mental samples (12 to 51%) in a U.S. study (Table 1.3). S. enterica has been isolated
from 1 to 7% of deer samples in two studies reported and up to 3% of wild bird
samples. A multidrug - resistant S. Newport strain was prevalent on two different farms
for months and shed by a cow for at least 190 days (Cobbold and others 2006), and,
as noted above, a strain of SE (PT30) has been isolated from almond orchard soil
periodically for at least 5 years (Uesugi and others 2007).
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Campylobacter Species
C. jejuni incidence in cattle, poultry, other farm animals, and wild animals has been
reported and reviewed (Miller and Mandrell 2006). Although the incidence of C. jejuni
reported in
20 studies is comparable or higher than those reported and listed for E.
coli O157 and Salmonella in Table 1.3, few major outbreaks of C. jejuni associated
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