Food Safety Challenges
from Farm to Table
Michael P. Doyle
Incidence of Foodborne Illness in
United States

Centers for Disease Control and
Prevention estimates 76 million cases
of foodborne illness annually
 Includes 325,000 hospitalizations
and 5,000 deaths
P. S. Mead et al. 5:607 (1999)
Comparison of Estimated Annual
Incidence of Foodborne Illness with
Other Illnesses in U.S.
Illness
No. of Cases
Bronchitis
Flu
Common cold
Foodborne disease
12 million
50 million
62 million
76 million
CDC estimates (2000)
Estimated Number of Cases of Foodborne
Illness Annually in United States
Cases from Foodborne Transmission
Norwalk-like viruses
9, 200,000
Campylobacter spp.
1,963,000
Salmonella (nontyphoid)
1,332,000
Clostridium perfringens
248,500
Giardia lamblia
200,000
Staphylococcus food poisoning
185,000
Toxoplasma gondii
112,500
Shigella spp.
90,000
Yersinia enterocolitica
86,800
P. S. Mead et al. Emerging Infect. Dis. 5:607 (1999)
Estimated Number of Cases of Foodborne
Illness Annually in United States
Cases from Foodborne Transmission
Escherichia coli O157:H7
62,500
Enterotoxigenic E. coli
55,600
Streptococcus
51,000
Astrovirus
39,000
Rotavirus
39,000
Shiga-toxin producing E. coli (nonO157)
31,000
Bacillus cereus
27,400
E. coli (other diarrheic)
23,900
Cyclospora cayetanensis
14,600
P. S. Mead et al. Emerging Infect. Dis. 5:607 (1999)
Estimated Number of Cases of Foodborne
Illness Annually in United States
Cases from Foodborne Transmission
Vibrio parahaemolyticus
Hepatitis A
Listeria monocytogenes
Brucella sp.
Botulism
Trichinella spiralis
Vibrio cholerae
Vibrio vulnificus
5,000
4,200
2,500
780
60
50
50
50
P. S. Mead et al. Emerging Infect. Dis. 5:607 (1999)
Leading Bacteriological Causes of
Foodborne Illness in USA




Campylobacter jejuni - est. 2 million cases/yr
 Principal vehicles - poultry, unpasteurized milk
Salmonella sp. - est. 1.5 million cases/yr
 Principal vehicles - eggs, poultry, beef, pork,
produce
Shigella - est. 90,000 cases/yr
 Principal vehicles - salads, produce (food handler
contamination)
E. coli O157:H7 - est. 60,000 cases/yr
 Principal vehicles - cattle (handling) and beef,
produce, water (recreational and drinking)
Transmission of Foodborne Pathogens


Campylobacter jejuni and Salmonella sp.
 Carried in intestinal tract of poultry and
other animals
 Fecal contamination of skin during
grow out and processing
Salmonella Enteritidis
–Colonize ovarian tissue of poultry
–Internal contents of eggs are
contaminated
Risk Factors for Sporadic Campylobacter
Infections in the United States

Case-control study of 6 FoodNet sites from Jan 98
- Mar 99 involving 1463 patients with
Campylobacter infection and 1317 controls

Risk factors include:
 Foreign travel
 Eating undercooked poultry
 Eating chicken or turkey cooked outside the home
 Eating nonpoultry meat cooked outside the home
 Eating raw seafood
 Drinking raw milk
 Living on or visiting a farm
 Contact with farm animals
 Contact with puppies
Transmission of Foodborne Pathogens

E. coli O157:H7
 Carried in intestinal tract of cattle
 Direct or indirect contact with cattle
manure is likely most frequent origin
Manure can contaminate food through:
-Use of manure as a soil fertilizer
-Polluted irrigation water
-Defecation of cattle in vicinity of
produce or foods of animal origin
Risk Factors Associated with
Sporadic Cases of E. coli O157:H7
Infection in U.S.


Eating undercooked ground beef
Visiting a farm
U.S. Centers for Disease Control and Prevention, 1998
Agricultural Practices

Major sources of foodborne pathogen
contamination of agricultural products
are: (1) animal manure and (2) human
feces (e.g., produce harvesting and
handling)
The Manure Glut: A Growing
Environmental Threat

Five tons of animal manure is produced
annually nationwide for every person living in
the United States


The amount of animal manure is 130 times
greater than the amount of human waste
produced
Cattle, hogs, chickens and turkey produced an
estimated 1.36 billion tons of manure in 1997
The U.S. Manure Glut (1997 estimates)
Animal
Solid Waste (Tons/yr)
Cattle
Hogs
Chickens
Turkeys
1,229,190,000
112,652,300
14,394,000
5,425,000
TOTAL
1.36 billion
Prevalence of Campylobacter in
Manure



Cattle manure
 Beef cattle at slaughter
Poultry manure
 Chickens and turkeys
Sheep manure
 Sheep at slaughter
89% prevalence
80-100% prevalence
(depending on flock)
high prevalence
Prevalence of Salmonella in
Manure

Cattle manure
- 10 to 25% of samples

Poultry manure - 29% of samples
E. coli O157 in U.S. Feedlots


USDA National Animal Health Monitoring
System determined prevalence of E. coli O157
in beef feedlots in 11 western and midwestern
states during Oct 99 - Sept 00
11.0% (1,148/10,415) of fecal samples were E.
coli O157-positive
USDA-APHIS, Fort Collins, CO. E. coli O157 in
United States Feedlots, October 2001
E. coli O157 in U.S. Feedlots

Prevalence of E. coli O157 in beef fecal
samples by month of collection
Oct 99
Nov 99
Dec 99
Jan 00
Feb 00
Mar 00
10.2%
11.1
8.9
5.7
3.3
4.7
Apr 00
May 00
Jun 00
Jul 00
Aug 00
Sep 00
15.6%
12.1
15.3
17.4
10.7
19.9
Reported Levels of Pathogens in
Animal Manures
Pathogen
Animal
Cattle
Poultry
(CFU or Oocysts/g)
Campylobacter
104 - 108
Salmonella up to 108 - 1010
E. coli O157:H7
102 - 105
Cryptosporidium 105 - 1010
104 - 107
104 - 107
—
—
Sheep
up to 105
108
107
What types of foods are most likely
to be contaminated with foodborne
pathogens?
Types of Foods Most Likely Contaminated
with Foodborne Pathogens

Fresh (unpasteurized) foods of animal
origin and plant-derived foods having
contact with manure or human sewage
 Milk
 Beef
 Poultry
 Pork
 Eggs
 Produce (e.g., lettuce, sprouts, fruit
juices, cantaloupe, cilantro)
Types of Foods Most Likely Contaminated
with Foodborne Pathogens

Foods prepared by an infected food handler
 Salads
 Salad bar foods
 Sandwiches
Emerging Issues in the
Microbiological Safety of Foods

Imported Foods

Sanitation practices for food
production and preparation are not
universally equivalent
Major Concern Regarding
Imported Food

Pathogens on produce
 Sources:
Irrigation water
Processing water
Poor personal hygiene of infected
foodhandlers
Sewage/manure used as soil fertilizer
 (Example) Shigellosis from Mexican-grown parsley
Prevalence of Salmonella and
Shigella on Imported Produce

FDA assayed 1003 imported produce
samples from March 99 - October 00 for
Salmonella, Shigella and E. coli
O157:H7
 35 positive for Salmonella
 9 positive for Shigella
 0 positive for E. coli O157:H7
Prevalence of Salmonella and
Shigella on Imported Produce
Produce Type
Broccoli
Cantaloupe
Celery
Cilantro
Culantro
Lettuce (loose-leaf)
Parsley
Scallions
Strawberries
Tomatoes
Total
No. Sampled
36
151
84
177
12
116
84
180
143
20
1003
No. Positive
0
11
3
16
6
2
2
3
1
0
44
Emerging Issues in the
Microbiological Safety of Foods

Antibiotic-Resistant Foodborne Pathogens
 Opportunistic pathogens become
untreatable
 Vancomycin-resistant enterococci
 Prevalent pathogens become life
threatening
 Multi-resistant Salmonella
Emerging Issues in the
Microbiological Safety of Foods

Non-O157:H7 enterohemorrhagic E. coli
 Examples of other serotypes of EHEC
O26:H11
O6:H31
O104:H21
O48:H7
O111:NM
O98:NM
O145:NM
O103:H2
O157:NM
E. coli O111:NM Outbreaks


23 cases of hemolytic uremic
syndrome from January February 1995 in South Australia
Vehicle was mettwurst (semi-dry
sausage)
Emerging Issues in the
Microbiological Safety of Foods

Foodborne Parasites

Global trade and a penchant for fresh,
uncooked/undercooked foods can be
a dangerous combination
Cyclospora cayetanensis

1996 Outbreak
 More than 1500 illnesses in 15 states and
Canada
 Vehicle - Guatemalan raspberries
Suggested source was untreated water
from natural reservoirs used to mix
pesticides sprayed on raspberries
Cyclospora cayetanensis

1997 Outbreaks
 Guatemalan (and possibly Chilean)
raspberries
5 states and a cruise ship
 Mesclun lettuce
 Pesto sauce (basil)
Toxoplasmosis


Estimated 112,500 food-associated cases
annually in United States
 Estimated 2,500 hospitalized cases and
375 deaths
In Europe, congenital toxoplasmosis affects
1 to 10 in 10,000 newborn babies
 1 to 2% develop learning disorders or die
 4 to 27% develop permanent impairment of
vision
Toxoplasma Infection in European
Pregnant Women


Case-control study in 6 European cities to
identify risk factors associated with
toxoplasmosis in pregnancy
Results:
 Between 30 and 63% of infections at different
centers were attributed to consumption of
undercooked (lamb, beef or game) and cured
meat products
 6 to 17% were attributed to soil contact
 Contact with cats was not a risk factor
A. J. C. Cook et al. Br. Med. J. 321:142 (2000)
Prevalence of Giardia and
Cryptosporidium in Dairy Herds
Assayed for parasites 2943 fecal samples from
cattle on 109 dairy farms
 8.9% positive for Giardia sp.
 0.9% positive for Cryptosporidium
parvum
 1.1% positive for Cryptosporidium muris
 Calves < 6 months of age
 20.1% positive for Giardia sp.
 2.4% positive for C. parvum
S. E. Wade et al. Vet. Parasitol. 93:1 (2000)

Emerging Issues in the
Microbiological Safety of Foods

Foodborne Viruses

A major but highly underreported
cause of foodborne illness

CDC estimates 9.2 million foodborne
cases of Norwalk-like virus annually in
U.S.