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 annuallyIncludes 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 12 million

Flu 50 million

Common cold 62 million

Foodborne disease 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 5,000

Hepatitis A 4,200

Listeria monocytogenes 2,500

Brucella sp. 780

Botulism 60

Trichinella spiralis 50

Vibrio cholerae 50

Vibrio vulnificus 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/yrPrincipal vehicles - poultry, unpasteurized milk

Salmonella sp. - est. 1.5 million cases/yrPrincipal vehicles - eggs, poultry, beef, pork, produce

Shigella - est. 90,000 cases/yrPrincipal 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 animalsFecal 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:H7Carried in intestinal tract of cattleDirect 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 1,229,190,000

Hogs 112,652,300

Chickens 14,394,000

Turkeys 5,425,000

TOTAL 1.36 billion

Prevalence of Campylobacter in Manure

Cattle manureBeef cattle at slaughter 89% prevalence

Poultry manureChickens and turkeys 80-100% prevalence

(depending on flock)

Sheep manureSheep at slaughter 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 10.2% Apr 00 15.6%

Nov 99 11.1 May 00 12.1

Dec 99 8.9 Jun 00 15.3

Jan 00 5.7 Jul 00 17.4

Feb 00 3.3 Aug 00 10.7

Mar 00 4.7 Sep 00 19.9

Reported Levels of Pathogens in Animal Manures

Pathogen Animal

Cattle Poultry Sheep (CFU or Oocysts/g)

Campylobacter 104 - 108 104 - 107 up to 105

Salmonella up to 108 - 1010 104 - 107 E. coli O157:H7 102 - 105 — 108 Cryptosporidium 105 - 1010 — 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 sewageMilkBeefPoultryPorkEggsProduce (e.g., lettuce, sprouts, fruit juices, cantaloupe,

cilantro)

Types of Foods Most Likely Contaminated with Foodborne Pathogens

Foods prepared by an infected food handlerSaladsSalad bar foodsSandwiches

Emerging Issues in the Microbiological Safety of Foods

Imported Foods

Sanitation practices for food production and preparation are not universally equivalent

Major Concern RegardingImported 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:H735 positive for Salmonella 9 positive for Shigella 0 positive for E. coli O157:H7

Prevalence of Salmonella and Shigella on Imported Produce

Produce Type No. Sampled No. Positive Broccoli 36 0

Cantaloupe 151 11

Celery 84 3

Cilantro 177 16

Culantro 12 6

Lettuce (loose-leaf) 116 2

Parsley 84 2

Scallions 180 3

Strawberries 143 1

Tomatoes 20 0

Total 1003 44

Emerging Issues in the Microbiological Safety of Foods

Antibiotic-Resistant Foodborne PathogensOpportunistic 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. coliExamples 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 OutbreakMore than 1500 illnesses in 15 states and

CanadaVehicle - Guatemalan raspberries

Suggested source was untreated water from natural reservoirs used to mix pesticides sprayed on raspberries

Cyclospora cayetanensis

1997 OutbreaksGuatemalan (and possibly Chilean)

raspberries5 states and a cruise ship

Mesclun lettucePesto sauce (basil)

Toxoplasmosis Estimated 112,500 food-associated cases annually

in United StatesEstimated 2,500 hospitalized cases and 375

deaths In Europe, congenital toxoplasmosis affects 1 to 10

in 10,000 newborn babies1 to 2% develop learning disorders or die4 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 contactContact 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.