Reserch Articles Swine Helth Impct on Crcss Contmintion nd Humn Foodorne Risk H. Scott Hurd, DVM, PhD Jen Brudvig, DVM, MPH Jmes Dickson, PhD Jovn Mircet, DVM c Miroslv Polovinski c Nel Mtthews, MS, PhD d Ronld Griffith, DVM, PhD SYNOPSIS Ojective. This study mesured the reltionship etween lesions suggestive of suclinicl pig illness t hrvest to crcss contmintion nd humn foodorne risk. Methods. Over the course of eight visits (Decemer 2005 to Jnury 2006), we swed 280 rndomly selected crcsses, during norml slughter opertions, t three points in the slughter line: skin pre-scld; the ung or pelvic cvity following removl of the distl colon nd rectum; nd pleurl cvity, immeditely efore the finl crcss rinse. Ech sw sponge ws used on five crcsses in ung nd pleurl cvity smpling. Sw sponges were cultured quntittively for Cmpylocter spp., Enterococcus spp., nd Enteroctericee spp., nd qulittively for Slmonell spp. Dt on helth indictors were collected for ll pigs in the study (2,625 pigs) y experienced plnt qulity ssurnce personnel. Results. Cmpylocter spp. were recovered from the pleurl cvity in 58.9% (33/56) of pools (five crcsses/pool), nd in 44.6% (25/56) of pools from the ung cvity. Enterococcus spp. were recovered from 66.1% (37/56) nd 35.7% (20/56) of pleurl nd ung pools, respectively. The most common lesion identified ws the peel-out (pleuritis or dhesions), with totl of 7.1% (186/2,625 totl hed). Liner regression showed tht for every percentge point increse in peel-outs, Enterococcus spp. contmintion incresed y 4.4% nd Cmpylocter spp. incresed y 5.1% (p 0.05). Conclusions. This study showed correltion etween niml helth nd humn helth risk, s mesured y crcss contmintion. Therefore, niml mngement decisions on-frm, such s housing, ntiiotic use, environment, nd level of veterinry cre, my directly impct pulic helth. Iow Stte University, College of Veterinry Medicine, Ames, IA Iow Stte University, College of Agriculture, Ames, IA c University of Novi Sd, Novi Sd, Seri Montenegro d Premium Stndrd Frms, Miln, MO Address correspondence to: H. Scott Hurd, DVM, PhD, College of Veterinry Medicine, Iow Stte University, VMRI Building 4, Ames, IA 50011; tel. 515-231-3720; fx 515-294-8793; e-mil <shurd@istte.edu>. 2008 Assocition of Schools of Pulic Helth 343
344 Reserch Articles Since the pssge of the Food nd Drugs Act in 1906, the pulic hs greed tht the consumption of helthy food nimls is in the est interest of pulic helth. 1 Tody, pulic helth risks not detected y trditionl visul inspection procedures in the pcking plnt include chemicl or ntiiotic residues nd foodorne pthogens. The one medicine concept, or the close ssocition of the medicl nd veterinry professions for the helth of ll species, 2 is often discussed; however, it is uncler how veterinry cre specificlly impcts pulic helth risks. Accurte quntifiction of this risk-risk reltionship etween niml helth nd pulic helth is essentil for effective policy-mking. The risk-risk pproch hs een pplied to some pulic helth issues in the U.S., such s the Environmentl Protection Agency s ssessment of cncer risk from chlorinted wter reltive to cteril risk from nonchlorinted wter. 3,4 To conduct these types of nlyses in the food sfety ren, the link etween niml nd humn helth needs to e mesured. Antemortem inspection usully removes cliniclly ill nimls from the humn food supply. However, sucliniclly ill nimls ppering helthy t slughter my hve internl lesions ffecting processing. These lesions my impct the eviscertion process leding to cross-contmintion nd incresed pthogen lod. Enterococcus is n indictor of fecl contmintion on the crcss. Cmpylocter spp. nd Slmonell spp. re common humn foodorne pthogens, nd thus indicte the level of pulic helth risk. Additionlly, these lesions often indicte chronic or resolved illnesses in the growing or finishing pig. 5 The ojective of this study ws to quntify the reltionship etween lesions detected t slughter nd cteril crcss contmintion. METHODS For cteriologicl evlution, we selected crcsses during norml slughter opertions in modern, verticlly integrted pork production compny. We swed three loctions on the crcsses t three different points in the slughter line: (1) the skin immeditely efore scld; (2) the ung (pelvic) cvity immeditely fter removl of the ung (distl colon nd rectum) ut efore eviscertion; (3) nd the pleurl cvity following complete eviscertion nd immeditely prior to finl crcss rinse. Becuse crcsses were not identified t the point of smple collection, it is likely tht we did not otin smples from ll three res on the sme crcss; i.e., we took only one smple from one of the three sites per crcss. We otined dt on eight different visits during Decemer 2005 nd Jnury 2006, with n verge of 328 pigs per group. In this opertion, pigs re mrketed from single rn on two or three seprte occsions. The first pigs mrketed re those first chieving cceptle weight. We smpled these first pull pigs the fstest-growing nd likely the helthiest first thing in the morning to minimize cross-contmintion mong workers, crcsses, nd mchinery. On Mondy, we collected smples from conventionl pigs, nd on Tuesdy from ntiiotic-free pigs. CON-rised pigs received ntiiotics for disese prevention or tretment, or performnce enhncement from lte nursery until ner slughter. ABF pigs were rised without performnce-enhncing/preventive or tretment ntiiotics. Cliniclly ill nimls requiring tretment were moved to seprte pens in the sme uilding nd were sent to mrket seprte from their ABF cohorts. Mngement of the two groups, excepting ntiiotic tretment, ws similr in veterinry cre, housing, environment, nd feed. Microiologicl comprison etween ABF nd CON pigs ws secondry ojective in this study, nd is not reported here. Helth indictors Experienced plnt qulity ssurnce (QA) personnel reported cses of the following helth indictors per group ( group represented ll pigs processed from one rn on tht dy): Ascessed heds: condemned heds due to visile scesses. Peel-outs (pleuritis or dhesions): the pleurl lining is removed fter eviscertion due to dhesions etween the pleur nd portions of the lung. Portions of the lung were usully ttched. Ftigued: nimls exhiit signs of neroic metolism, including respirtory distress (open-mouth rething), reluctnce to move, or recumency. Bcteriology Specimen collectors wore ltex gloves nd chnged gloves etween ech smpling. We swed the crcsses with Whirl-Pk Speci-Sponges (Nsco, Ft. Atkinson, Wisconsin) sws hydrted with 10m sterile 0.1% peptone wter. For the pre-scld smples, one sponge ws used for ech crcss. However, for the ung (pelvic) nd pleurl cvity smpling, one sponge ws used for five crcsses pooling method commonly used in Denmrk to llow for the incresed efficiency needed to detect the expected low numer of Slmonell spp. positive crcsses. 6 The interior surfce of the pelvic, dominl, nd thorcic cvity ws swed, covering s much re s possile in the short time ville, s crcsses were still moving down the line. Sponges were
Swine Helth Impct on Crcsses nd Humns 345 mintined on ice during trnsport to the lortory. We minimized differences in storge times etween the two groups y immeditely trnsporting smples to the lortory on Mondy nd Tuesdy fternoons. In the lortory, we enriched sponges with 15mL sterile 0.1% peptone wter, stomched the sponges (Sewrd Stomcher 3500, Worthing, West Sussex, UK) for one minute, serilly diluted the smples in 0.1% peptone wter, nd then plted on selective grs for Cmpylocter spp., Enteroctericee spp., nd Enterococcus spp. We complied with Nnnpneni 7 in Cmpylocter gr (CA) preprtion y comining Cmpylocter enrichment roth (Bolton formul, LAB 135; J&K Microiologics, Inc., North Ridgeville, Ohio) with 1.5% gr (Becton Dickinson Microiology Systems, Sprks, Mrylnd), mixing Cmpylocter selective ntiiotic supplement (X132, J&K Microiologics, Inc.) nd 5% lysed defirinted horse lood (MT 59074; Qud Five, Ryegte, Montn) thoroughly efore pouring CA pltes. We septiclly spred 100µL of diluted smples onto CA pltes in duplicte. The pltes were incuted in Form Tri-gs incutor (5% O 2, 10% CO 2, 85% N 2 ) t 42 C nd evluted t 24 nd 48 hours. To isolte Enterococcus spp., we septiclly spred 100µL of diluted smple onto Enterococcosel gr (Difco, Becton Dickinson Microiology Systems) in duplicte nd incuted for 24 hours t 35 C. Similrly, we isolted Enteroctericee spp. y septiclly spreding 100µL of diluted smple onto violet red ile gr with glucose (VRBG, Difco, Becton Dickinson Microiology Systems) in duplicte (24 hours t 37 C). For Slmonell spp., we enriched the remining uffer nd sponge sw in uffered peptone wter, nd screened these with n ntigen-cpture enzyme-linked immunosorent (Revel Slmonell; Neogen, Lnsing, Michign) ssy to determine presumptive Slmonell spp. positives. Presumptive positive smples were enriched in tetrthionte roth (24 hours t 37 C) nd streked for isoltion on XLD gr (24 hours t 37 C). Colonies exhiiting typicl slmonell morphology nd phenotypic rections were trnsferred to Triple Sugr Iron gr (TSI) nd Lysine Iron gr (LIA) slnts. Colonies showing typicl slmonell-like rections on TSI nd LIA were confirmed using the BBL Crystl Enteric/ Nonfermenter ID kit, following the mnufcturer s instructions. Slmonell spp. colonies were serotyped t the U.S. Deprtment of Agriculture (USDA) Animl nd Plnt Helth Inspection Service (APHIS) Ntionl Veterinry Services Lortory. Sttisticl nlysis We compred the mens of the vriles etween the CON nd ABF groups with t-tests nd the Wilcoxon rnk sum test. We did not use the nonprmetric Chi-squre test s it requires comining ll the CON smples into single group, nd there ws sustntil vrince etween the oservtions y replicte. We evluted the ssocition etween helth (percent lesions) nd contmintion (percent of pools positive) with liner regression using ivrite liner regression etween ll possile pirs of contmintion nd helth. Contmintion ws the response vrile. For the regression, the helth nd the contmintion vriles tht were percentges (rnge50 100) were treted s unounded continuous vriles. Becuse the helth nd the contmintion vrile vlues in the CON group differed sustntilly from those in the ABF group, we used multivrite regression y forcing the ntiiotic use group (ABF or CON) indictor vrile into the model. We lso utilized multivrite liner regression to determine whether the quntity of cteri (log of the most prole numer) ws ssocited with niml helth indictors. RESULTS On ech visit, 35 crcsses were swed t ech loction (ung [pelvic] cvity, pleurl cvity, skin pre-scld). One sponge ws used for five crcsses, resulting in seven pools of crcsses swed per replicte, except for pre-scld, where only one sponge ws used. A totl of 280 crcsses over eight replictes were swed, resulting in 56 pools for culture. Tle 1 shows the results of cteril contmintion y loction on the crcss. In Tle 1, n represents the numer of crcsses ville for swing in prticulr replicte nd the numer oserved for helth indictors (Tle 2). Enteroctericee spp. ws recovered in high percentge of the pools, rnging from men of 82.1% pre-scld (46/56 pools) to 96.4% (54/56 pools) of ung sws. Slmonell spp. ws recovered in reltively low percentge of pools, rnging from men of 8.9% in oth the ung nd pleurl cvities (5/56 pools) to 17.9% (10/56 pools) pre-scld. Becuse the level of cteri on the skin pre-scld is less mesure of food sfety nd more n indictor of how dirty the pigs re t slughter, we excluded this pre-scld mesure from further nlyses. One experienced plnt QA person oserved ll crcsses (2,625 hed) for helth-relted lesions. Results re shown in Tle 2. The most common lesion identified ws the peel-out, with totl of 7.1% (186/2,625 totl hed). Ascessed heds were found in 1.7% (44/2,625) of crcsses. Antemortem signs of ftigue were recorded in 0.5% (13/2,625) of oserved nimls. Similr to contmintion rtes, vritions in helth sttus existed etween replictes. Tle 3 shows
346 Reserch Articles Tle 1. Bcteril contmintion of swine crcsses t slughter collected from three different points in the slughter process: skin pre-scld, pelvic (ung), nd pleurl cvities Numer positive out of 7 pools Orgnism nd loction Rep. 1 n 337 Rep. 1 n 326 Rep. 2 n 332 Rep. 2 n 338 Rep. 3 n 320 Rep. 3 n 320 Rep. 4 n 316 Rep. 4 n 336 Percent of positive pools (n 56) Slmonell pre-scld 1 2 0 1 2 1 1 2 17.9 Slmonell ung 1 1 0 0 0 0 1 2 8.9 Slmonell pleur 1 4 0 0 0 0 0 0 8.9 Enterococcus pre-scld 4 7 4 7 7 7 5 7 85.7 Enterococcus ung 2 0 3 2 6 1 6 0 35.7 Enterococcus pleur 7 6 3 3 4 6 7 1 66.1 Enteroctericee pre-scld 4 7 7 7 0 7 7 7 82.1 Enteroctericee ung 7 7 7 6 7 7 7 6 96.4 Enteroctericee pleur 7 7 7 6 7 7 6 5 92.9 Cmpylocter pre-scld 0 0 2 4 0 0 3 0 16.1 Cmpylocter ung 3 3 7 1 4 1 6 0 44.6 Cmpylocter pleur 2 3 6 5 7 2 7 1 58.9 CON nimls received ntiiotics for growth promotion nd disese prevention nd tretment; ABF nimls never received ntiiotics. n numer of crcsses ville for testing in ech Rep. CON conventionlly rised ABF ntiiotic-free Rep. replicte comprison of helth nd contmintion etween ntiiotic use groups. There ws no sttisticlly significnt (p 0.05) difference in helth indictors etween groups. While ABF pigs hd more scessed heds thn CON pigs (2.7% compred with 0.7%, p=0.06), cteril contmintion ws consistently higher in the CON pigs. For only this reson, the ntiiotic use group ws included s covrite in the regression models mesuring the reltionship etween helth nd contmintion. Tle 4 shows the results for regression nlysis etween helth indictors nd percent of crcsses contminted. Although some confidence intervls (CIs) re estimted s less thn zero, ll of the predicted Tle 2. Helth indictors for swine t hrvest Numer positive (out of n hed oserved) Helth indictor Rep. 1 n 337 Rep. 1 n 326 Rep. 2 n 332 Rep. 2 n 338 Rep. 3 n 320 Rep. 3 n 320 Rep. 4 n 316 Rep. 4 n 336 Totl (n 2,625) (percent) 95% CI Peel-out c 15 16 13 46 34 19 36 7 186 (7.10) 6.10, 8.07 Ascessed heds d 0 9 4 2 0 13 5 11 44 (1.70) 1.20, 2.20 Ftigue e 4 3 3 0 2 0 1 0 13 (0.50) 0.20, 0.76 CON nimls received ntiiotics for growth promotion nd disese prevention nd tretment; ABF nimls never received ntiiotics. n numer of crcsses ville for testing in ech Rep. c Pleuritis or pleurl dhesions usully requiring removl of the cvity lining d Heds condemned due to visile scess(es) e Aneroic metolism, respirtory distress, recumency CON conventionlly rised ABF ntiiotic-free Rep. replicte CI confidence intervl
Swine Helth Impct on Crcsses nd Humns 347 Tle 3. Comprison of the key helth indictors nd contmintion rtes etween ABF nd CON pigs Vrile Totl percent in CON groups (n 1,305 pigs) Totl percent in ABF groups (n 1,320 pigs) P-vlue for two-sided t-test Peel-out 7.60 6.63 0.77 Ascessed heds c 0.69 2.67 0.06 Ftigue d 0.76 0.23 0.12 Cmpylocter in pleurl cvity 78.50 39.30 0.11 Cmpylocter in ung cvity 71.40 17.00 0.02 Enterococcus in ung cvity 60.70 10.70 0.02 CON pigs received ntiiotics for growth promotion nd disese prevention nd tretment; ABF pigs never received ntiiotics. Pleuritis nd pleurl dhesions c Heds condemned due to visile scess(es) d Aneroic metolism, respirtory distress, recumency ABF ntiiotic-free CON conventionlly rised Rep. replicte vlues were within the intervl (rnge50 100). These results indicte tht s the percentge of sucliniclly ill nimls (evidenced y peel-outs [pleuritis or dhesions] nd ftigue) increses, so does the percentge of crcsses with cteril contmintion. We found the strongest positive reltionships etween the percentge of peel-outs nd Cmpylocter spp. contmintion in the pleurl cvity (β55.7) nd etween peel-out percent nd Enterococcus spp. contmintion in the ung (pelvic) cvity (β55.1). In the multivrite model (ntiiotic use s covrite), these reltionships were sttisticlly significnt (p 0.05), s shown y the 95% CIs tht do not include zero. We lso identified nother positive reltionship etween the percentge of ftigued pigs nd Cmpylocter spp. contmintion in the ung cvity. The Figure grphiclly shows the reltionship etween helth nd contmintion: s the percentge of peel-outs in group increses y 1 percentge point, the pleurl Cmpylocter spp. contmintion increses 5 percentge points, nd Enterococcus spp. contmintion in the ung increses 4.4 percentge points. We identified negtive reltionships etween cteril contmintion nd the percentge of scessed heds in the group. In the multivrite regression, s the percentge of scessed heds incresed, Cmpylocter spp. contmintion in the pleur decresed (β5 6.2), s did Enterococcus spp. in the ung (β5 2.5). Tle 4. Regression coefficients (univrite nd multivrite with ntiiotic use group s covrite) etween percentge of representtive helth vriles nd percentge of crcsses positive for Enterococcus spp. or Cmpylocter spp. in the ung or pleurl cvities, Helth indictor Bcteril contmintion Loction on crcss Regression coefficient (ß) (univrite) 95% CI Regression coefficient (ß) (multivrite) 95% CI Ftigued c Cmpylocter Bung 41.0 ( 19.0, 102.0) 10.0 ( 50.0, 70.0) Peel-outs d Cmpylocter Pleur 5.7 ( 0.3, 11.7) 5.1 (0.4, 9.9) Peel-outs Enterococcus Bung 5.1 ( 1.3, 11.5) 4.4 (1.3, 7.4) Ascessed heds e Cmpylocter Pleur 12.7 ( 31.0, 5.0) 6.2 ( 33.0, 21.0) Ascessed heds Enterococcus Bung 13.3 ( 31.0, 0.5) 2.5 ( 24.0, 19.0) All helth nd contmintion reltionships were tested. Only those with p 0.2 in the univrite comprison re shown. Conventionlly rised nimls received ntiiotics for growth promotion nd disese prevention nd tretment; ntiiotic-free nimls never received ntiiotics. c Aneroic metolism, respirtory distress, recumency d Pleuritis nd pleurl dhesions e Heds condemned due to visile scess(es) CI confidence intervl
348 Reserch Articles Neither of these negtive correltions ws sttisticlly significnt in this dtset. Additionlly, Tle 5 shows sttisticlly significnt reltionships etween the percentge of peel-outs in the group nd the quntity (log of the men colony forming units, log 10 CFU) of Enterococcus spp. present in the ung cvity (β50.38). A positive correltion ws lso identified etween the quntity of Cmpylocter spp. in the pleurl cvity nd the percentge of peel-outs. DISCUSSION This study shows correltion etween lesions suggestive of suclinicl niml illness nd humn helth risk, s mesured y crcss contmintion (Cmpylocter spp., Enterococcus spp.). 5 The rtionle cn e understood from the impct of niml helth on the eviscertion process: ntemortem inspection processes typiclly remove cliniclly ill nimls. However, if disese is not outwrdly evident or hs resolved, leving old lesions, these ill nimls my go undetected until eviscertion. In previous studies, 50% of normlities went undetected y Europen Commission inspection methods. 8 Insufficient or imprecise eviscertion ws shown to impct the proility of crcss contmintion nd microil lod more thn other processes in slughter. For exmple, Enteroctericee spp. contmintion incresed from 4% to 40% during processing from polishing (eginning) to post-eviscertion (end). 8 Dressing, splitting, nd met inspection cn ccount for 85% to 90% of crcss contmintion. 9,10 Therefore, lesions ffecting eviscertion qulity will ffect pulic helth risk y incresing crcss hndling nd crosscontmintion. Helth conditions tht ffect eviscertion qulity include peritonitis, pleuritis, dhesions, volume nd fluidity of gut contents, gut friility, nd ny helth condition tht leds to dditionl hndling (skin lesions, ruises, scesses, rthritis). Helth indictors One experienced plnt QA person recorded the helth indictors used in this study, which reflect orgnoleptic (ssessment y sight nd touch) inspection issues tht must e ddressed in the slughter process. The definition of peel-out, or ftigued pig, is specific from met-inspection perspective, ut is not specific veterinry pthologicl dignosis. The precise pthologicl mening of the indictors needs to e defined. The Figure. Reltionship (multivrite liner regression) etween percentge of peel-outs nd crcss contmintion with Cmpylocter spp. in the pleur (%Cmpy PL) nd Enterococcus spp. in the ung cvity (%Ecocc B) in pig crcsses cultured during processing
Swine Helth Impct on Crcsses nd Humns 349 Tle 5. Regression coefficients of the quntity (log10cfu/ml) of Cmpylocter spp. nd Enterococcus spp. present in the pleur nd ung, nd the percentge of peel-outs in slughter pigs Bcteril contmintion Log men CFU Log men CFU Regression coefficient (multivrite) 95% CI Cmpy pleur 4.66 2.88 0.39 ( 0.27, 1.05) Ecocci ung 2.95 2.47 0.38 ( 0.1, 0.86) Ecocci pleur 3.23 1.04 0.25 ( 0.35, 0.85) CON nimls received ntiiotics for growth promotion nd disese prevention nd tretment. ABF nimls never received ntiiotics. CFU colony-forming units CON conventionlly rised nimls ABF ntiiotic-free nimls Cmpy Cmpylocter spp. Ecocci Enterococcus spp. CI confidence intervl 13 ftigued pigs in this study exhiited signs of rethlessness nd difficulty in moving. After dditionl rest in the pens, they were multory, nd pssed USDA Food Sfety nd Inspection Service (USDA:FSIS) veterinry inspection for norml slughter. Future reserch should etter define the specific pthologicl dignosis of these helth indictors. Reserch hs shown tht pthology in the thorx, such s pleuritis nd dhesions, is likely due to respirtory disese erlier in life. 5 Crcsses requiring peel-out typiclly hve portions of the lung ttched to the pleur. Although ftigue nd peel-outs re indirect mesures of pig helth, oth of these vriles were correlted with n incresed mount of cteril crcss contmintion, nd thus wrrnt further explortion. The ojective of this study ws not to compre ABF nd CON pigs. These groups were studied s prt of n ojective, reported elsewhere, to compre ntiiotic resistnce ptterns. 11 Given the dt collected, comprison etween these two groups is tenuous. Although ABF nd CON nimls were rised with similr mngement, feed, nd housing, ABF pigs likely represent different popultion thn CON pigs. The ABF group included only fster-growing nimls tht were never treted with ny ntiiotic, representing the est of the est. Ill nimls in the ABF group were removed from tht group nd treted, remining in seprte pens until slughter. CON pigs my hve received previous tretment for clinicl illness. Consequently, in these dt, comprison of helth prmeters etween ABF nd CON is to e voided, especilly without more detiled dt such s moridity/mortlity rtes, rte of gin, nd feed efficiency. However, due to the higher contmintion rtes in the CON group, this vrile proved to e n importnt confounder in our regression models. Bcteril contmintion The loctions tested for contmintion (ung [pelvic] nd pleurl cvities) reflect two temporl extremes of the slughter process nd the crcss itself. The ung cvity ws swed erly in processing, while the pleurl cvity ws swed t the end of the slughter process, when the crcss represents ner-finl product entering the cutting nd friction process. Higher levels of Enterococcus spp. contmintion might e expected in the ung, which lies in close proximity to the nl orifice. However, Cmpylocter spp. hve een recovered from tonsils, stomch, ileum, cecum, colon, nd lymph nodes. 12 The ssocition etween pthology, such s peel-outs nd Cmpylocter spp. contmintion, does not suggest tht Cmpylocter cuses swine respirtory disese. Pssive inhltion of scld wter hs een implicted in contmintion of the lungs. Tering of the lungs during eviscertion my llow tht pssive contmintion onto the pleur. 13 Regression reltionships We descrie reltionships in these dt etween percent of group of pooled smples nd percent helth lesions oserved in trucklod of pigs. Smple pooling is n efficient mens to test more crcsses, which cn e used to estimte individul crcss prevlence of Slmonell spp. 5 However, in this study, we compred the percent positive pools rther thn estimting crcss prevlence. The sttisticl results reflect the reltively lower power of only seven oservtions (pools) per replicte. Therefore, it is noteworthy tht sttisticlly significnt correltions were detected with such smll study. The helth mesures, such s peel-outs, re not specific veterinry pthologicl dignoses; however, if there is ny misclssifiction, it would hve occurred nondifferentilly, mong the contminted nd noncontminted crcsses.
350 Reserch Articles The liner regression models suggest tht for every percentge point increse in lesions, there is 4 to 5 percentge point increse in contmintion. The Figure nd the CIs in Tles 4 nd 5 show the uncertinty round these predicted increses. This uncertin informtion cn e used in risk-risk models to estimte the impct of veterinry cre on humn helth risk. While it is uncler why cteril contmintion rtes were so much higher in the CON group (Tle 3), multivrite nlysis with ntiiotic use s covrite djusted for this oservtion. Therefore, the multivrite regression coefficients shown in Tle 4 illustrte the reltionship etween helth nd contmintion, even though contmintion in CON pigs ws higher. An insignificnt negtive ssocition ws noted etween scessed heds nd cteril crcss contmintion (Tle 4). A hed ws condemned if there were visile scesses (pockets of inflmmtory cells in res such s muscles or lymph nodes). Crcsses with visile hed scesses were more likely to e removed from the processing line for further inspection or condemntion. Given our study design, these crcsses would not e ville for cteriologicl exmintion t either the ung or pleurl loctions, producing negtive ssocition. While few studies hve reported miniml correltion etween lesions nd pthogen contmintion within the lesion, 14,15 these studies use different method. They focused on detecting the pthogen in the lesion site, not on pprently helthy prts of the crcss. Pulic helth implictions Implictions to humn helth found in this study uild on the ssumption tht swine crcss contmintion is resonle proxy for humn helth risk. USDA: FSIS inspection stndrds ccept this ssumption. The prevlence of Slmonell positive swine crcsses is the stndrd for meeting Hzrd Anlysis nd Criticl Control Point requirements. 16 In Denmrk, gols for swine Slmonell control re set reltive to crcss contmintion rtes, nd the sme stndrds re used in the Europen Union community. 17 Creful modeling of the swine slughter process corroorted this ssumption. Both Dutch nd Dnish scientists report tht reducing crcss contmintion is the most effective wy to reduce pulic helth risk. 18 21 Notly, some of these studies reported tht control methods fter crcss rinse (e.g., friction nd cutting) would not e effective due to dditionl cross-contmintion. 18 CONCLUSION This study gives preliminry indiction of risk-risk reltionship etween niml nd humn helth, which hs een explored y others. Russell showed tht decresed poultry helth t processing increses the proility of crcss contmintion with Cmpylocter spp. nd Slmonell spp. 22 Others hve shown tht smll chnges in niml helth cn hve lrge impcts on the numer of foodorne illness dys, even when djusting for the hypotheticl increse in illness dys from resistnt infections. 23,24 If the findings from this study cn e supported y further reserch nd repetition, then humn foodorne illness risk is impcted y swine helth. Therefore, niml mngement decisions onfrm such s housing, ntiiotic use, environment, nd veterinry cre directly impct pulic helth. The uthors thnk Ssidhr Mlldi for ssistnce in dt nlysis; Brend Ptton, Deprtment of Animl Science, for dt collection nd cteriology; nd Elnco Animl Helth, Greenfield, Indin, for prtil funding. At the time of puliction, Dr. Hurd ws serving s Deputy Undersecretry for Food Sfety t the U.S. Deprtment of Agriculture (USDA) Food Sfety nd Inspection Service. 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