Agriculture Reference
In-Depth Information
Animal Sources of Enteric Foodborne Pathogens Relevant to
Produce Contamination
Carriage of pathogens by food animals is a critical factor relevant to many outbreaks
associated with produce, meat, milk, and other food products. Evidence for the colo-
nization of cattle (Elder and others 2000; Hussein and Bollinger 2005; Fegan and
others 2005; Low and others 2005; Dargatz and others 2003), swine (Chapman and
others 1997; Jay and others 2007), sheep (Ogden and others 2005), poultry (Chapman
and others 1997; Rose and others 2002; Foley and others 2008; McCrea and others
2006), and multiple species of wild animals (Ejidokun and others 2006; Hernandez
and others 2003; Kirk and others 2002; Sargeant and others 1999; Pritchard and others
2001; Wetzel and LeJeune 2006) by
E. coli
O157:H7,
S. enterica
, and
C. jejuni
(Miller
and Mandrell 2006) has been documented. Pathogen colonization of livestock and
wild animals is a dynamic process depending upon how and when pathogens are
encountered in the environment (food, grass, water), pathogen fi tness in the environ-
ment and animal GI tracts (viability, dose), animal contact/commingling and move-
ment, immunity, and fecal shedding. In addition, there are unknown factors that might
enhance or diminish pathogens in particular environments, for example, weather
conditions, feed, predation, or antimicrobials. One or more of these factors may be
important in initiating or contributing to the size of an outbreak.
Studies documenting the incidence of
E. coli
O157:H7 and
Salmonella
in animals
are summarized in Table 1.3. Details regarding the methods, periods, locations, and
samples studied can be obtained from the original papers cited.
E. coli
O157:H7 and Non-O157 STEC
Cattle are major carriers of
E. coli
O157, non - O157 shigatoxin - positive
E. coli
(STEC),
S. enterica
and
C. jejuni
strains (Table 1.3). Strains of the same serovars
as those associated with produce outbreaks have been isolated frequently from
cattle. Similarly, sheep, pigs, chickens, and turkeys are common or intermittent
carriers of these pathogens, and a variety of wildlife species carry these pathogens
or related pathogens (Tables 1.1 and 1.3). For example,
E. coli
O157:H7 and non-
O157 STEC strains have been isolated from deer (Keene and others 1997; Sargeant
and others 1999; Fischer and others 2001; Dunn and others 2004; Renter and others
2006), feral swine (Jay and others 2007), pigeons (Morabito and others 2001),
seagulls (Makino and others 2000), starlings, horses, dogs (Hancock and others
1998 ), barn fl ies (Keen and others 2006), and slugs (Sproston and others 2006).
Salmonella
has been isolated from deer (Branham and others 2005; Renter and
others 2006), badgers (Nielsen and others 1981), wild mice (Tablante and Lane
1989), wild turtles and tortoises (Hidalgo-Vila and others 2007), and a variety of
wild birds (Fenlon 1981; Wahlstrom and others 2003; Hughes and others 2008). The
concentration of pathogen in wildlife samples is not well documented; thus, the
shedding status of wildlife compared to livestock is unclear. Moreover, the quantity
of feces shed by different species of wildlife per animal or for a population in a
region is unknown, so data relevant to the total amount of pathogen disseminated
by a species in any spatial and temporal context also are unknown. The amount of
pathogen shed by an animal is extremely relevant epidemiologically for identifying
