Environmental Engineering Reference
In-Depth Information
1974 and 1975, probably due to hygienic processing, pasteurization, and qual-
ity control,
44
but bulk and cracked eggs are a recurring problem as vehicles
for foodborne salmonella.
42
Hauschild and Bryan found that for a total of 26
outbreaks of salmonellosis the median ratio of estimated cases to initial human
isolations of salmonella was 29.5.
35
On this basis, the actual number of cases of
human salmonellosis for the period 1969 to 1978 was estimated to be 740,000 in
the United States and 150,000 in Canada annually.
35
Although estimates differ,
they do show the seriousness of the problem and the need for more effective
control methods. The overall national salmonellosis morbidity has remained rel-
atively constant. The average number of isolates has actually increased since
1976 except for the years 1980 and 1984. Surveillance by the Foodborne Dis-
eases Active Surveillance Network (FoodNet) has similarly found that despite
decreases in the incidence of many foodborne pathogens,
Salmonella
infections
have remained relatively constant over time. Of the six most common
Salmonella
serotypes, only one declined in 2006 from baseline levels.
45
Additionally, because
Salmonella
can be transmitted to human via many vehicles, including produce,
eggs, poultry, meat, and contact with animals, efforts to control
Salmonella
must
take into account many potential sources of infection. Several recent outbreaks
of
Salmonella
, including one associated with peanut butter,
46
and one associ-
ated with tomatoes
47
underscore the diverse routes of infection and the need to
more effectively prevent contamination of food products. Salmonellosis control
involves use of salmonella-free feeds; strict hygiene in the handling and prepa-
ration of food for human consumption; education of managers, inspectors, and
foodhandlers; time-temperature control in food preparation; and prohibition of
antibiotics in animal feed (cattle, hogs, poultry), which may promote the growth
of drug-resistant organisms that can spread to humans.
Milk and Other Dairy Products
Raw milk (including certified) or improperly pasteurized milk, poor milk-
handling and processing practices, postpasteurization contamination, and
improper refrigeration have been associated with outbreaks caused by contami-
nated milk. Soft cheeses and other dairy products have also been associated with
a number of foodborne outbreaks. Raw milk and raw milk products have been
associated with outbreaks of a number of pathogens, including
Salmonella
spp.,
Camylobacter, Listeria, Staphylococcus aureus
(staphylococcus enterotoxin),
Streptococcus agalactiae, Mycobacterium tuberculosis, Listeria monocytogenes
,
and
Yersinia enterocolitica
. A recent review found 46 raw-milk-associated
outbreaks reported to CDC from 21 states during 1973 to 1992, including 57
percent caused by
Campylobacter
and 26 percent caused by
Salmonella
.
48
Sev-
eral recent multistate outbreaks of
Salmonella
associated with the consumption
of raw milk have been reported.
49
,
50
The largest milkborne outbreak on record occurred in the Chicago area in
March and April of 1985. Two brands of two percent low-fat pasteurized milk
were implicated.
Salmonella typhimurium
was found in 16,284 culture-confirmed
