30 Microbial Safety of Food and Food Products 697tended shelf life. Listeriosis infections often result in
septicemia and/or meningitis. The case mortality
ratio for Listeriosis infections is much higher than
those of Salmonella, Campylobacter,and E. coli
0157:H7 infections. An estimated 500 deaths associ-
ated with Listeriosis are reported annually in the
United States. Individuals most susceptible to Lis-
teriosis include the elderly, the young, immunocom-
promised patients, and pregnant woman. A wide
variety of foods including processed meats, milk
and dairy products, fruits,and vegetables have been
implicated in a number of Listerioses outbreaks. In
1999, a multistate outbreak involving 1000 cases of
Listeriosis in the United States was linked to con-
sumption of contaminated hot dogs and delicatessen
meats, resulting in a recall of 35 million pounds of
these food products (MMWR 1999).
VEROTOXIGENICESCHERICHIA COLI(VTEC)
INFECTIONS
Verotoxigenic Escherichia coli(VTEC) belonging
to the O157 serogroup is the most common VTEC
serogroup implicated in foodborne disease out-
breaks. This organism was first recognized as a
cause of hemorrhagic colitis in 1982. VTEC O157
and serogroups O5, O26, and O111 are of high
prevalence in feces of healthy cattle. Thus, foods of
animal origin such as meat, milk, and dairy products
can be contaminated with these organisms. Other
types of foods such as salads, vegetables, fruits,
sandwiches, and cooked meat can be contaminated
during preparation. Contaminated water can also be
a source of infection by this organism. The majority
of food- and waterborne outbreaks had links with
contamination of fecal origin. Infection by VTEC
can result in hemorrhagic colitis (HC) and hemolyt-
ic uremic syndrome (HUS), abdominal pain, and
watery diarrhea (bloody or nonbloody). The HC
symptoms may lead to complications of the HUS
and subsequent renal failure. Although HUS can
occur in any age group, children are more suscepti-
ble (Karmali 1989). In adults, 50% of thrombocy-
topenic purpura (TP) cases are caused by HUS.
Other bacterial foodborne infections can occur as
a result of ingestion of food contaminated with Sta-
phylococcus aureustoxin, Clostridium perfringens,
Clostridium botulinumtoxin, Shigellaspp., Yersinia
enterocolitica, Brucellaspp., Vibrio cholera, Vibrio
paraheamolylicus, and Bacillus cereusenterotoxin.
FOODBORNEPARASITEINFECTIONSFoodborne parasite infections are caused by certain
groups of protozoa. It is believed that foodborne
infections related to parasites are underreported by
an estimated factor of 10 or more (Casemore 1991),
and the etiological agent of foodborne outbreaks is
identified in less than 50% of the cases (Bean et al.
1990, Cliver 1987). Parasites commonly associated
with foodborne disease and possible food and water
sources are listed in Table 30.3.
Cryptosporidium parvumis the species of Cry-
ptosporidiumassociated with infection in humans
(Current and Blagburn 1990). It is a common cause
of gastrointestinal infections in immunocompro-
mised individuals and is an opportunistic pathogen
associated with infections in patients with acquired
immune deficiency syndrome (AIDS), but it affects
healthy people as well. Although drinking water
contaminated with human or animal feces is the usu-
al source of transmission of this organism to hu-
mans, epidemiological links between the consump-
tion of contaminated foods such as raw sausage,
offal, and raw milk and cryptosporidiosis have been
reported (Casemore 1990, Casemore et al. 1986).
The largest outbreak of waterborne cryptosporidio-
sis was reported in Milwaukee, Wisconsin, with
403,000 persons ill. Reported outbreaks in most
countries are associated with contaminated drinking
water or contaminated swimming pools.
Cyclosporais an emerging pathogen, which caus-
es diarrheal infections in humans. The first reported
outbreak of Cyclosporainfection occurred in 20
U.S. states and two provinces in Canada, Ontario
and Quebec, during the months of May and June,
1996, and April and May, 1997. Consumption of
contaminated imported raspberries was implicated
in many of these outbreaks (Herwaldt and Ackers
1996, Herwaldt and Beach 1997). Contaminated
mesculun lettuce and basil have also been linked to
Cyclosporaoutbreaks (MMWR 1997).
Sarcocytisis another coccidian parasite, which is
prevalent in livestock. Human infection occurs as a
result of ingestion of raw or undercooked meat con-
taining mature sarcocysts (Tenter 1995).
Toxoplasma gondiiis an intracellular parasite,
which is prevalent in man and animals (Fayer 1981).
Ingestion of raw or undercooked meat from live-
stock and game animals is often implicated in hu-
man toxoplasmosis infections. Another parasite