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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 HealthFt. Collins, CO
Summary of Results from NAHMS Studies
• NAHMS – National Animal Health Monitoring System
• Program of USDA Animal and Plant Health Inspection Service (APHIS)
• Program Goal: Provide information on animal health of livestock and poultry throughout the U.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
Pathogens in Feedlots - 1994
• 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
Pathogens in Feedlots - 1994
• 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
Pathogens in Feedlots - 1994
• 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
Pathogens in Feedlots - 1994• 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
Pathogens in Feedlots – 1999/2000
• 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
Pathogens in Feedlots – 1999/2000
Percent Samples Positive for Salmonella
4.02.8
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
Pathogens in Feedlots – 1999/2000
• 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
Pathogens in Feedlots – 1999/2000
Percent Samples Positive for E. coli O157
10.2 11.18.9
5.73.3
4.7
15.6
12.1
15.317.4
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 cowson-farm
Cows to beculled
Cull cows atmarkets
Feb-AprMay-JulTotal
Percent of Samples with VT E. coli O157
NAHMS Dairy ‘96 Study
http://nahms.aphis.usda.gov/Dairy_Cattle/ecosalm98.htm
0
10
20
30
40
50
60
Farm Market
Feb-AprMay-JulTotal
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 – environmental samples– 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 between
flocks– 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
3.72.3
7.3
0.00.02.04.06.08.0
10.012.014.016.018.020.0
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 19951. Derby2. Agona3. Typhimurium cop4. Brandenberg5. Mbandaka6. Typhimurium7. Heidelberg8. Anatum9. Enteritids BA10.Worthington
Swine 20001. Derby2. Agona3. Typhimurium cop4. Heidelberg5. Brandenberg6. Typhimurium7. Worthington8. Anatum9. Infantis10.Tennessee
Swine – 1995
• SalmonellaFactor 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 epidemiologic studies
• Data from large epidemiologic studies should be used to generate hypotheses to be evaluated in more controlled experiments
• More research is needed to evaluate interventions (biosecurity and active measures)
More Information Available
USDA:Centers for Epidemiology and Animal Health
555. S. Howes
Ft. Collins, CO 80521
970 490-8000
NAHMSWEB@aphis.usda.gov
nahms.aphis.usda.gov
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