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Pathogen Reduction Dialogue

Panel 1

May 6, 2002

Food Safety Pathogens on the

Farm

David A. Dargatz DVM PhDUSDA:APHIS Centers for Epidemiology and Animal Health

Ft. Collins, CO



Summary of Results from NAHMS

Studies

• NAHMS – National Animal Health MonitoringSystem

• Program of USDA Animal and Plant Health

Inspection Service (APHIS)• Program Goal: Provide information on animal

health of livestock and poultry throughout theU.S.

• Approach to Pathogens – Estimate prevalence

– Evaluate risk factors

• Primary focus – Salmonella and E. coli O157



Production Systems

• Feedlot cattle (1994 and 1999)

• Dairy (1996)

• Layers (1999)• Swine (1995 and 2000)



Pathogens in Feedlots - 1994

• 100 feedlots in 13 states

• Samples collected from Oct – Dec

• Laboratory evaluation

– Salmonella

• 2 pens of cattle

• culture, serotype

– E. coli O157

• 4 pens of cattle

• historical culture methods




• Results

– Salmonella

• 38% of feedlots with 1+ positive samples

• 5.5% (273/4,977) of samples positive

• Most common serotypes (65% of isolates)

– S. Anatum

– S. Montevideo

– S. Muenster

– S. Kentucky

– S. Newington

Fedorka-Cray et al. J. Food Protection 61:525




• Results

– Salmonella

• Factors associated with positive pens

– Tallow – Whole cottonseed or cotton seed hulls

• Factors not associated with positive pens – Region

– Operation size

– Use of sprinklers

– Time on feed

– Type of cattle

– Cattle density

– Other feed ingredients

Losinger et al. Prev. Vet. Med. 31:231




• Results

– E. coli O157

• 63% of feedlots 1+ positive samples

• 1.8% (210/11,881) of samples positive

Hancock et al. J. Food Protection 60:462




• Results

– E. coli O157

• Factors associated with positive pens

OR

– Short time in feedlot (<20 days) 3.39

– Barley feeding 2.75

– Light entry weights (<700) 1.85

– Steers 3.03

• Factors not associated with positive pens

– Region

– Operation size

– Animal density

– Ionophore use

– Other feed ingredients

Dargatz et al. J. Food Protection 60:466



Pathogens in Feedlots – 1999/2000

• 73 feedlots in 11 states

• Samples collected from Oct 1999 – Sept 2000

– Each feedlot visited twice

• Laboratory evaluation

– Salmonella

• 3 pens

• Culture, serotype

– E. coli O157

• 3 pens

• immunomagnetic bead separation




• Results

– Salmonella

• 51% of feedlots with 1+ positive samples

• 6.3% (654/10,417) of samples positive• Most common serotypes (72% of isolates)

– S. Anatum*

– S. Montevideo*

– S. Reading

– S. Newport

– S. Kentucky*

• Risk factor evaluation underway

http://nahms.aphis.usda.gov/Beef_Feedlot/99sal.pdf




Percent Samples Positive for Salmonel la

4.0

2.8

6.8

11.4

0.0

2.0

4.0

6.0

8.0

10.0

12.0

Oct-Dec Jan-Mar Apr-Jun Jul-Sep




• Results

– E. coli O157

• 100% of feedlots 1+ positive samples

• 11% (1,148/10,415) of samples positive

– Early 13.9%

– Random 10.6%

– Late 8.6%

• Risk factor evaluation underway

http://nahms.aphis.usda.gov/Beef_Feedlot/coli.PDF




Percent Samples Positive for E. co li O157

10.2 11.18.9

5.7

3.3

4.7

15.6

12.1

15.3 17.4

10.7

19.9

0

5

10

15

20

25

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep



Dairy 1996

• Operations in 19 states – 91 dairies

– 97 markets

• Samples collected from Feb – Jul – Milk cows (n=3,640)

– Cull cows on farm (n=668)

– Cull cows in markets (n=2,287)

• Laboratory evaluation – Salmonella – culture, serotype

– E. coli O157 – historical culture methods



Dairy 1996 – Salmonella

• Overall cow-level prevalence – Milk cows 5.4%

– Expected culls 18.1%

– Culls at markets 14.9%

• Most common serotypes (63.2%) – S. Montevideo

– S. Cerro

– S. Kentucky – S. Menhaden

– S. Anatum

– S. Meleagridis

Wells et al. J. Food Protection 64:3



Dairy 1996 - Salmonella

• 21.1% of operations had milk cows shedding

• 25.9% of operations had expected culls

shedding

• Salmonella shedding on dairies related to

OR

– Larger herd size – 100 or more cows 5.8

– Southern region 5.7 – Use of recycled flush water 3.5

– Brewer’s products fed 3.4

Kabagambe et al. Prev Vet Med 43:177-194



0

1

2

3

4

5

Milk cows

on-farm

Cows to be

culled

Cull cows at

markets

Feb-AprMay-Jul

Total

Percent of Samples with VT E. coli O157NAHMS Dairy ‘96 Study

http://nahms.aphis.usda.gov/Dairy_Cattle/ecosalm98.htm



0

10

20

30

40

50

60

Farm Market

Feb-Apr

May-Jul

Total

Percent of Operations with VT E. coli O157

NAHMS Dairy ‘96 Study

http://nahms.aphis.usda.gov/Dairy_Cattle/ecosalm98.htm



Dairy 1996

• Factors associated with dairy operations

positive for E. coli O157

OR

– Samples collected after May 1 7.7

– Flush alleyways with water 8.0

Garber et al., J Food Protection 62:307



Dairy 1996

• Factors not associated with shedding of E.

coli O157 on dairy farms

– Manure handling practices

– Chlorination of water tanks

– Grazing

– Housing type

– Diet components (protein, fat, byproducts,probiotics, alfalfa)

Garber et al., J Food Protection 62:307



Layers - 1999

• 200 layer houses – environmentalsamples

– Manure

– Egg belts – Elevators

– Walkways

• 129 layer houses – rodents collected• Laboratory evaluation

– Salmonella enterica serotype Enteritidis



Layers - 1999

• 7.1% of layer houses positive

• 3.7% of house mice were positive

• Factors associated with positive houses

– Flocks < 60 weeks

– Not cleaning feeders or hoppers betweenflocks

– Higher number of rodents

http://nahms.aphis.usda.gov/Poultry/lay99SEhi.htm



Layers - 1999

Percent of Houses and Mice SE Positive

4.4

9.0

17.2

0.0

3.7

2.3

7.3

0.00.0

2.04.0

6.0

8.0

10.0

12.0

14.016.0

18.0

20.0

West Central Great Lakes Southeast

Houses

Mice

http://nahms.aphis.usda.gov/Poultry/lay99SEhi.htm



Swine – 1995 and 2000

• Swine 1995

– 152 operations in 16 states

• At least 300 grower/finishers

– Up to 50 samples per site from late finishers• Total of 6655 samples

• Swine 2000

– 124 operations from 17 states

• At least 100 head inventory

– Up to 50 samples per site from late finishers

• Total of 5509 samples



Swine – 1995 and 2000

Salmonella

Prevalence 1995 2000

Herd 38.2% 34.7%

Sample 6.0% 6.6%



Salmonella serotypesSwine 1995

1. Derby

2. Agona

3. Typhimurium cop

4. Brandenberg

5. Mbandaka

6. Typhimurium

7. Heidelberg

8. Anatum

9. Enteritids BA

10.Worthington

Swine 2000

1. Derby

2. Agona

3. Typhimurium cop

4. Heidelberg

5. Brandenberg

6. Typhimurium

7. Worthington

8. Anatum

9. Infantis

10.Tennessee



Swine – 1995

• Salmonella

Factor Level OR (95% CI)

Mix on farm Yes .4 (.2 -.9)

AO (never) Some, most, all 2.5 (1.1 – 5.9)

Resp Culls (0) .01 - .25 .3 (.1 – 1.3)

> .25 .2 (.1 - .8)

Pen Sex (mixed) Single only 2.8 (1.0 – 7.8)

Both types 5.4 (1.8 – 16.3)

Region (SE) North .2 (.1 - .6)

Midwest .2 (.1 - .7)

Meal (Yes) No 26.4 (2.8 – 249)



Swine 1995 – E. coli O157

• E coli O157:H7• Tested a subset (4,229) of Salmonella fecal

samples

• All were negative



Pathogens on the Farm -

Conclusions• Widely distributed geographically and by operation type

– Region generally not a factor

– Similar prevalence for Salmonella across operation types

• Mostly present in low numbers or low prevalence

• Inconsistent risk factors identified across epidemiologicstudies

• Data from large epidemiologic studies should be used togenerate hypotheses to be evaluated in more controlledexperiments

• More research is needed to evaluate interventions

(biosecurity and active measures)



More Information Available

USDA:Centers for Epidemiology andAnimal Health

555. S. Howes

Ft. Collins, CO 80521

970 490-8000

[email protected]

nahms.aphis.usda.gov

food safety pathogens on the fafood safety pathogens on the farm

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