1

Agents of Foodborne Zoonoses• Illness caused by

– Campylobacter spp.– Escherichia coli O157:H7– Salmonella

• 80-95% cases from these bacteria estimated tobe foodborne; probably of animal origin

• FoodNet data (repeat???)– PulseNet: Molecular epidemiology

• Outbreaks and investigations• Carriage by food animals and food• Risk

Foodborne Diseases ActiveSurveillance Network (FoodNet)

• Principal foodborne disease component ofCDC's Emerging Infections Program

• Active surveillance for foodborne diseases andrelated epidemiologic studies (PulseNet) tobetter understand the epidemiology of foodbornediseases in the United States.

• “Active” surveillance system, meaning publichealth officials frequently contact laboratorydirectors to find new cases of foodbornediseases and report these cases electronically toCDC.

FoodNet Disease Monitoring• Bacteria

– Campylobacter– Escherichia coli O157– Listeria monocytogenes– Salmonella– Shigella– Vibrio– Yersinia enterocolitica

• Parasites– Cryptosporidium– Cyclospora

• Viruses– Hepatitis A– Noroviruses

FoodNet

• 1995, FoodNet surveillance began in fivelocations: California, Connecticut, Georgia,Minnesota and Oregon

• New York and Maryland in 1998,Tennessee in 2000, Colorado in 2001 andNew Mexico in 2004).– The total population of the 2004 bacterial

catchment is 44.5 million persons, or 15.1% ofthe United States population.

Mead et al (1999)

Reported and Estimated Illnesses:Foodborne pathogens--US

Mead et al (1999)

2

Foodborne Disease - US (1998-2002)(Reported)

From FoodNet and Mead et al (1999)

(Estimated)

Relative Rates vs 1996-1998 Baseline

FoodNet

FoodNet 2006

FoodNet

Incidence/105

Outbreaks 1998-2002

After FoodNet Kimura et al (2004)

3

After FoodNet

Campylobacteriosis

FoodNet

Campylobacteriosis

http://www.cdc.gov/foodnet/annual/2004/Tables.pdf

All Sites California

Foodborne Illness Cases(Top 10 Salmonella Serotypes)

FoodNet

Reported Outbreaks and Cases—US (1998)

4

Outbreak Investigations

• Subtyping• PulseNet• E. coli O157

– Hamburger– Spinach

• Salmonella• Campylobacter

– Manning et al (2003)

Subtyping• ID cases likely to be part of an outbreak• Eliminate sporadic cases (background noise)• Difficult to select appropriate method

– Tenover et al. (1997)• Salmonella

– Bender et al (2001)– McQuiston et al (2004)

• E. coli O157:H7– Samadpour (1995)

• Campylobacter– Manning et al (2003)

Methods used for typingE. coli O157:H7 strains

• Toxin gene screening

• Plasmid profiling

• Phage typing

• Antibiotic susceptibility testing

• Restriction fragment lengthpolymorphism with bacteriophageλ (λ -RFLP)

• Ribotyping;• Pulsed-field gel electrophoresis• PCR using randomly amplified

polymorphic DNA (RAPD)sequences

• PCR using highly repetitivesequences (rep-PCR)

• Amplified fragment lengthpolymorphism analysis

• Thomas et al., 1996; Ostroff et al.,1989

• Ostroff et al., 1989; Paros et al., 1993;Meng et al., 1995; Radu et al., 2001

• Ahmed et al., 1987; Khakhria et al.,1990; Barrett et al., 1994

• Kim et al., 1994; Farina et al., 1996;Radu et al., 2001;

• Paros et al., 1993;Samadpour et al.,1993

• Martin et al., 1996; Roberts et al., 2001• Bohm and Karch, 1992;Barrett et al.,

1994;Meng et al., 1995;Radu et al.,2001

• Swaminathan and Barrett,1995; Raduet al., 2001

• None specific for E. coli-O157:H7;Johnson and O’Bryan, 2000

• Iyoda et al., 1999; Zhao et al., 2000

How Does PulseNet Work?1. PFGE2. Pattern electronic database at local,

state or federal level3. Uploaded to national database at CDC4. CDC searches for clusters of patterns5. Local cluster searches6. Clusters posted to Listserve.

5

Changes in Outbreaks

• Food consumption and practices in UShave changed during the past 20 years

• Shift from the typical point source, or“church supper” outbreak, which isrelatively easy to detect to the morediffuse, widespread outbreaks that occurover many communities with only a fewillnesses in each community.

Changes in OutbreaksContinued• Large food producing facilities that disseminate

products throughout the country• Some few outbreaks that some low level

contamination of food products• Products are distributed among many states• Only a few illnesses occur in each community,• New laboratory and statistical tools, such as

PulseNet and the surveillance outbreakdetection algorithm (SODA), impact ability toidentify and investigate these new types ofoutbreaks

How does subtyping help inepidemiologic investigations?• Identifies cases within an outbreak• Distinguishes outbreak cases from concurrent

sporadic cases• Reduces misclassification• Detects outbreaks through surveillance• Links apparently sporadic cases

– Cases may be too widely dispersed to detect– Organism too common to notice small increase– Identifies related cases and separates them from

unrelated ones• DNA “fingerprinting” methods have greatly

increased sensitivity of subtyping

Increases sensitivity of outbreak detection

Rangel, J.M. et al. Emerg. Infect. Dis. 11: 603-609 (2005)

outbreakdetected 1993

Meat recall

1993 Western States E. coli O157 Outbreak

732 cases4 deaths

39 d

outbreak detected 2002

18 d

Swaminathan

Prevalence in Food Products

• E. coli O157:H7– Beef– Fruits and vegetables

• Salmonella– Poultry, beef, hogs– Eggs, fruits, vegetables

• Campylobacter– Poultry

6

Fresh ProduceOutbreaks--US

(1977-1999)

Sivapalasingam et al. (2004)

Some pathogenic E. coli(Simplified)

LT/STenterotoxigenic stx+

eae+

EHEC

O157:H7

E. coli

stx Assay on Vero CellsFiltrate Control

Speirs et al (1977)

E. coli O157:H7 Outbreak--1993

• Western states• >500 laboratory-confirmed infections• 4 deaths• O157:H7 known in hamburger since 1982

– Wells et al. (1983)• Prompted FSIS to declare O157:H7 an

adulterant in raw ground beef (1994)– Product often undercooked

Leafy Greens Outbreaks

Buchanan

MMWR

7

MMWR

SalmonellaFarm and Processing Plant

McCrea et al. (2006)

Salmonella poona: Cantaloupes

• April—June 2000– 47 cases; 5 states

• April—May 2001– 50 cases; 5 states

• March—May 2002– 58 cases; 14 states and provinces

Anderson et al. (2002)

PR/HACCP Salmonella “A” Sets(1998-2006)

After: http://www.fsis.usda.gov/science/Progress_Report_Salmonella_Testing_Tables/index.asp

PR/HACCP Salmonella “A” Sets

http://www.fsis.usda.gov/PDF/Salmonella_9year_Figures.pdf Sarwari et al. (2001)

8

Broilers Ground Turkey

Hogs Ground Beef

Rigney et al. (2004)

1998-2000

Heinitz et al (2000)

CampylobacterFarm and Processing Plant

McCrea et al. (2006)

Campylobacteriosis in Iceland

Stern et al. (2003)

Campylobacter Prevalence (US)Chicken Carcass Rinses

Stern and Pretanik (2006)

20042003

0

0

0

Campylobacter Prevalence (US)Chicken Carcass Rinses

Stern and Pretanik (2006)

9

Risk Factors

• Mostly exposure to food• Exposure to animals

Risk Factors S. enteric serotypeEnteritidis (FoodNet 02-03)

Marcus et al. (2006)

Friedman et al (2004)

Transfer of Campylobacter

Luber et al. (2006)

10

E. coli O157:H7 Risk Factors(FoodNet 1999-2000)

Voetsch et al (2006)