Salinas Valley, Monterey County

Transcription

1 Irrigation mediated transfer of E. coli O157:H7 from feces to lettuce, 211 & 212 Rob Atwill, Jennifer Chase, M. Jay, L. Harris, R. Bond, M. Partyka, WCFS field & lab crew Western Center for Food Safety, UC Davis David Oryang, Sherri Dennis, RTI International (M. Anderson, A. Mokhtari), ARS-Salinas, etc. Technical Forum on Produce Safety JIFSAN & FDA, College Park, MD February 8-9, 217 Primary vertebrate source(s) and key mechanism(s) of E. coli O157:H7 contamination of leafy green commodities in the preharvest production environment Salinas Valley, Monterey County Exclude wildlife by fencing, trapping and habitat modification Produce Fields consumed raw no kill step billions of servings Rangeland beef cattle wildlife habitat Montane & Chaparral beef cattle and wildlife habitat Salinas River riparian corridors wildlife habitat Comparing livestock to wildlife shedding of key foodborne zoonotic pathogens Cow-calf herds, central coastal CA, E. coli O157 infection ranged from % to 1% Herd pos n prev (%) A 489. B C 2. D E 61. F G H I 138. Total

2 CA statewide survey of 2 cow-calf herds, Butte, Contra Costa, Humboldt, Kern, Lassen, Madera, Modoc, Mono, San Joaquin, San Luis Obispo, Solano, Stanislaus, Tulare and Yuba County (14 counties) 1412 cows and calves Prevalence (%) of fecal shedding (positive/total) Salmonella E. coli O157 Cryptosporidium Giardia duodenalis Cow.4% (3/726) 5% (37/726) 9% (67/726) 23% (168/726) Calf.15% (1/686) 5% (35/686) 2% (136/686) 42% (286/686) TOTAL.3% (4/1412) 5.1% (72/1412) 14.4% (23/1412) 32% (454/1412) Sierra Foothill Research & Extension Center, University of California Buffer width (m).1, 1.1, 2.1 Land slope (%) 5, 2, 35 RDM (kg/ha) 225, 56, 9, 45 Rangeland buffers appear to retain 95% of E. coli in winter and spring; >99.9% achievable under certain conditions Tate et al., 26. J. Environ. Qual. 35: Wildlife and beef cattle from central coastal CA, 28-1 E. coli O157:H7 Feral pig 1/2 (5%) Coyote 2/95 (2%) Am. crow 5/93 (5%) Cowbird 2/6 (3%) Rabbit /18 (%) Skunk /63 (%) Tule elk 3/15 (2%) Deer /447 (%) Rodents 2/143 (.2%) Beef cattle 68/2715 (2.5%) Salmonella enterica wildlife 17/449 (3.8%) cattle 1/795 (.13%) wildlife shedding was 3 times higher compared to cattle (P<.1) Wildlife often congregate in groups Prevalence = 5% What is the probability of 1 positive bird in this group of 1 crows? 4% 2

3 Prevalence of pathogens in wild rodents in produce fields, central California, n=8113 trap nights, 13% trap success (171 rodents) E. coli O157:H7 2/1,43 (.2%) Salmonella 3/1,43 (2.9%) ~5% S. enterica subsp. arizonae (IIIA) ~3% S. I 6,8:d:- Winter precipitation runoff versus summer tail-water flows cow-calf ranches 1.4 to 7 deer mice/acre.5 to 2.7 cattle/acre Rodent species Cryptosporidium Giardia CA parasitic mouse 11% 13% Deer mouse 33% 27% Dusky-footed wood rat 17% 17% Total 26% 24% Cryptosporidium: oocysts/g feces; ~5% appear infectious for humans Giardia appears not infectious to humans Kilonzo et al., 213, Appl. Environ. Microbiol. 79(2): produce field 1 to 34 deer mice / acre (mean of 8.5 mice / acre) cattle in produce field Field trials of romaine lettuce: fecal transfer during irrigation ARS Salinas, California, July CFU of E. coli O157:H7 in 5 grams rabbit fecal slurry Feces Atwill et al., 215. J. Food Prot. 78(2): Bed Furrow Bed Timeline for Exp A & B irrigate on 7/14/211 Exp A days between fecal deposit and irrigate irrigate beds 11-3 F before irr, F F F samples 168 spot fecal all 27 plants immeidately after irrigate days between fecal spot and harvest Exp B SF after irr, beds 31-5 SF after irr SF after irr SF after irr SF after irr total samples F = fecal deposit, = sample lettuce, SF = spot fecal total samples Time between fecal deposition and irrigation (-3, -2, -1,.1 dy), wind aspect, distances between lettuce to fecal and fecal to mean sprinkler Beds Sp Sp F F3 F2 F1 F1 F2 F3 3

4 Probability to detect E. coli O157:H7 Fecal deposit 5 gm / cluster July 211 rabbit only July & October 212 rabbit & pig 1 tech depositing fecal to minimize error Tootsie-Rolls (aka fecal patties) ~1:1 fresh feces : PBS-E. coli O rabbit feces 212 rabbit & pig feces Homogenized with stomacher 5 gm field patties 1 gm validation patties 1-fold serial dilutions 3 concentrations x 3 reps No significant difference between field/lab Lettuce sampling after irrigation High concentration assay Detection limits mpn/head 2 6 mpn (1ml ) 1-fold serial dilutions Low concentration assay Detection limits 211: mpn/head 212: mpn/head 4 3 mpn (5, 1, 5, 1ml) 211: 3 3 mpn (1, 1, 1ml) 1. Sensitivity of MPN protocol to detect E. coli O157:H7 on heads of Romaine lettuce 2.5 hours of overhead irrigation using Nelson rotator emitters 1.25 to 3.85 mm applied E. coli O157:H7 (CFU/1 ml) 38% of lettuce heads within 7 cm (28 in) of scat had an average E. coli O157:H7 after irrigation (1.3 to 23, MPN). Relative to the original load of CFU of E. coli O157:H7 in 5 g, about.57 (.6%) transferred to the outer leaves of lettuce. 4

5 E. coli O157:H7 / head lettuce E. coli O157:H7 / head lettuce Log (C t /C ) for E. coli O157:H7 MPN per head of lettuce Log (C t /C ) for E. coli O157:H7 MPN per head of lettuce 2.5 hours of overhead irrigation using Nelson rotator emitters 1.25 to 3.85 mm applied Negative binomial regression: C t = e (α+ßx i ), [log(e(y X) = α+ßx] Log(C t /C o ), with C o set at MPN E. coli O157:H7/head asymmetric application of irrigation water ponding in furrows leaking irrigation pipe variable winds (NW) variable fog in am; sunshine in pm 38% of lettuce heads within 7 cm (28 in) of scat had an average E. coli O157:H7 after irrigation (1.3 to 23, MPN). Relative to the original load of CFU of E. coli O157:H7 in 5 g, about.57 (.6%) transferred to the outer leaves of lettuce. distance between feces and lettuce age of scat inches hours inches hours 2 inches 48 hours inches hours Mean distance of sprinklers to scat (inches) Mean distance of sprinklers to scat (inches) 1,, E. coli O157:H7 per head of Romaine lettuce 1, E. coli O157:H7 per head of Romaine lettuce Animal intrusion <24 hrs prior 1, 1, 1 1 1, 1 Worst case: animal intrusion immediately prior to last irrigation for lettuce in proximity to scat Distance between lettuce and fresh scat (inches) Age of scat (hrs) prior to irrigation 5

6 3 (ft) a b c a b c a b c a b c 285 a b c a b c a b c d e f a b c d e f d e f d e f F1-R F1-R F2-P a b c a b c a b c d e f d e f F1-P F-P F-P ### ### a b c a b c 46 a b c 23 d e f ### ### ### d e f d e f 3 19 d e f d e f F4-R F2-R F-P F4-P F2-R F-P ### ### 75 ### ### ### ### ### 82 a b c a b c a b c a b c a b c a b c Sp Sp Sp Sp Sp Beds F2-P Log (C t /C ) for E. coli O157:H7 in scat 3 E. coli O157:H7 remaining in scat post irrigation Age of scat (hours) Rodent traps set each day of experiment 9 rodents trapped, 4 separate individuals 3 for adult female tag 226 (lactating) 4 for adult male tag 227 (positive on 3 rd ) Fig 5 Field trials of romaine lettuce: fecal transfer during irrigation ARS Salinas, California, July-August and October 212 positive control strain from male deer mouse #227 F2-R F1-P ### F2-P ### ### d e f d e f d e f Sp Sp Sp Sp Sp F1-P F2-R F-R F1-R F2-P F-R F4-R a b c a b c 485 ### ### d e f d e f d e f d e f d e f d e f d e f a b c a b c a b c 17 ### 43 9 ### ### ### d e f 4 d e f d e f d e f F-R F1-R F4-R F4-R a b c a b c a b c a b c 4 d e f 1 d e f ### d e f F-R F4-P F1-P a b c 1 19 a b c ### a b c d e f d e f F4-P F4-P Field Schematic Highway Fence line Dirt Road 12 (ft) Dirt Road 3 (ft) Sprinklers 6

7 Log 1 (C t /C o ) E. coli O157 MPN/fecal Irrigation-mediated fecal transfer onto Romaine lettuce Salinas, CA 212 E. coli O157:H7 remaining in feces post irrigation Percent pos. (p/n) Percent transfer Mean MPN/head Range MPN/head Fecal C start Fecal C e / C end C s Aug 1, irrigate mm Pig 49% (47/96).1% , Rabbit Feces Aug Rabbit 76% (73/96).65% 23, , Oct 21, irrigate mm Pig 7% (67/96).7% 12, , Pig Feces Rabbit 79% (73/93).5% 9, , Median.7% 6 MPN C end MPN 211: spike CFU, 38% positive,.6% transfer ~5 hrs ~1 day ~2 days Age of feces (hrs) at collection ~4 days FSMA 215: Minimize fecal contamination from domestic and wild animals in the produce field: Farmers are required to take all measures reasonably necessary to identify and not harvest produce that is likely to be contaminated. Requires all covered farms to visually examine the growing area and all covered produce to be harvested, regardless of the harvest method used. 7