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Keeping Foodborne Pathogens Down on the Farm Michael P. Doyle.

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1 Keeping Foodborne Pathogens Down on the Farm Michael P. Doyle

2 Leading Bacteriological Causes of Foodborne Illness in USA l Campylobacter jejuni - est. 2 million cases/yr s Principal vehicles - poultry, unpasteurized milk l Salmonella sp. - est. 1.5 million cases/yr s Principal vehicles - eggs, poultry, beef, pork, produce l E. coli O157:H7 - est. 60,000 cases/yr s Principal vehicles - cattle (handling) and beef, produce, water (recreational and drinking)

3 Transmission of Foodborne Pathogens l Campylobacter jejuni and Salmonella sp. s Carried in intestinal tract of poultry and other animals s Fecal contamination of skin during grow out and processing l Salmonella enteritidis –Colonize ovarian tissue of poultry –Internal contents of eggs are contaminated

4 Transmission of Foodborne Pathogens l E. coli O157:H7 s Carried in intestinal tract of cattle s Direct or indirect contact with cattle manure is likely most frequent origin u Manure can contaminate food through: a.Use of manure as a soil fertilizer b.Polluted irrigation water c.Defecation of cattle in vicinity of produce or foods of animal origin

5 Prevalence of Risk Factors for Foodborne Illnesses in the General Population l Approximately 7,500 adults in CA, CT, GA, MN and OR were interviewed by telephone between July 1996 and June 1997 s 30% ate pink hamburger s 18% ate running eggs s 1.9% ate raw shellfish s 1.5% drank raw milk s 7% did not wash cutting board after cutting raw chicken s 7% did not wash their hands after handling raw meat or poultry B. Shiferaw et al. J. Food Protect. 63:1538 (2000)

6 Risk Factors for Sporadic Campylobacter Infections in the United States l Case-control study of 6 FoodNet sites from Jan 98 - Mar 99 involving 1463 patients with Campylobacter infection and 1317 controls s Risk factors include: u Foreign travel u Eating undercooked poultry u Eating chicken or turkey cooked outside the home u Eating nonpoultry meat cooked outside the home u Eating raw seafood u Drinking raw milk u Living on or visiting a farm u Contact with farm animals u Contact with puppies C. Friedman et al. Abstr. Int Conf Emerg Infect Dis 2000 No. 63. P

7 Risk Factors for Fluoroquinolone-Resistant Campylobacter Infections l Case-control study of 7 FoodNet sites from s 94 of 858 (11%) isolates from Campylobacter infections were fluoroquinolone-resistant s Risk factors include: u Eating chicken or turkey cooked at a commercial establishment u Storing raw chicken in refrigerator without plate to catch drippings u Travel outside the United States H. Kassenborg et al. Abstr. Int Conf Emerg Infect Dis 2000 No. 63, P. 150

8 Risk Factors Associated with Sporadic Cases of E. coli O157:H7 Infection in U.S. l Eating undercooked ground beef l Visiting a farm U.S. Centers for Disease Control and Prevention, 1998

9 Risk Factors Associated with E. coli O157:H7 Infections in Scotland 1. Handling / preparing raw food (40%) 2. Involved in gardening / garden play (36%) 3. Lived on / visited farm (20%) 4. Direct / indirect contact with animal manure (17%) 5. Private water supplies (12%) 6. Recent failures with high coliform counts of water supplies (12%) J. E. Coda et al., J. Infect. 36:317, 1998

10 Risk Factor Associated with E. coli O157:H7 Infections in Sweden Risk Factor l Contact with farm animals and farms Swedish Government Recommendations l Between June 1 to October 31, farmers with cattle, sheep or goats should avoid: s Visits to animal houses by unauthorized people, especially children under the age of 5 avoid contact with cattle s Consuming unpasteurized milk and dairy products s Contact between grazing animals and humans sunbathing on nearby beaches B. de Jong, Smittskydd 4:48, 1998

11 Risk Factor Associated with Shiga Toxin- Producing E. coli Infections in Canada l Determined spatial relationship between livestock density and human STEC incidence s Based on 3001 cases of STEC (>95% E. coli O157:H7) infection from in Ontario, Canada Michel et al. Epidemiol. Infect. 122:193 (1999)

12 Risk Factors Associated with STEC Infections in Canada l Results: s Areas with high incidence of STEC cases were situated predominantly in areas of mixed agriculture (high in rural areas compared to urban areas) s Cattle density had a positive association with incidence of STEC cases SElevated risk of STEC infection in rural populations associated with living in areas with high cattle density

13 Risk Factors Associated with STEC Infections in Canada l Conclusions: s Importance of contact with cattle and cattle manure likely has been previously underestimated as a risk factor for STEC infections

14 Calf to Human Transmission of E. coli O157:H month-old boy hospitalized with bloody diarrhea in October 1992; lived on dairy farm in SW Ontario -E. coli O157:H7 phagetype 23 isolated from stool 2.Boy placed on straw between calves while mother did barn chores -Boy frequently touched calves and put his fingers in their mouths and his 3.Fecal culture of 1 of 7 calves tested positive from E. coli O157:H7 phagetype 23 Renwick et al. J. Infect. Dis. 168:792 (1993)

15 E. coli O157:H7 Transmission via a Dog 1. Three-year-old U.K. girl developed E. Coli O157:H7 infection after petting a dog at a farm visitor center 2. Girl had no other contact with animals or dirt 3. An identical strain of O157:H7 was recovered from cattle on the farm Parry et al Lancet 346:8974

16 E. coli O157:H7 Infection from Vegetables 1.39-year-old lacto-ovo-vegetarian woman in Maine had E. coli O157:H7 infection 2.She lived on a farm and her diet consisted almost exclusively of vegetables from her garden - Garden fertilized with manure from calf and cow 3.E. coli O157:H7 was isolated manured soil from the garden Cieslak et al., Lancet 342:367 (1993)

17 Outbreak of E. coli O157:H7 Infections Associated with Farm Visits l 51 cases of E. coli O157:H7 infection associated with visiting a petting farm in Pennsylvania during Sept-Nov 2000 s 16 patients hospitalized, 8 with HUS l Case-control study identified physical contact with cattle as major risk factor (OR = 10.94) s Hand washing before eating was protective (OR = 0.23) l O157:H7 isolates from humans, 27 of 216 (13%) cattle and a handrailing all had same PFGE profile l Household survey estimated that 7,000 people developed diarrhea associated with visiting the farm J. A. Crump et al. Centers for Disease Control and Prevention (2001)

18 The Manure Glut: A Growing Environmental Threat l Five tons of animal manure is produced annually nationwide for every person living in the United States s The amount of animal manure is 130 times greater than the amount of human waste produced s Cattle, hogs, chickens and turkey produced an estimated 1.36 billion tons of manure in 1997 Democratic Staff of U.S. Senate Agriculture Committee (1998) “Animal Waste Pollution in America: An Emerging National Problem”

19 The U.S. Manure Glut (1997 estimates) AnimalSolid Waste (Tons/yr) Cattle 1,229,190,000 Hogs 112,652,300 Chickens 14,394,000 Turkeys 5,425,000 TOTAL 1.36 billion

20 Prevalence of Campylobacter in Manure l Cattle manure s Beef cattle at slaughter 89% prevalence l Poultry manure s Chickens and turkeys80-100% prevalence (depending on flock) l Sheep manure s Sheep at slaughterhigh prevalence

21 Prevalence of Salmonella in Manure l Cattle manure - 10 to 25% of samples l Poultry manure - 29% of samples

22 Prevalence of E. coli O157:H7 in Manure l Cattle manure s Weaned dairy calves5% s Unweaned dairy calves2% s Cattle at slaughter 13-28%

23 Reported Levels of Pathogens in Animal Manures PathogenAnimal CattlePoultrySheep (CFU or Oocysts/g) Campylobacter up to 10 5 Salmonella up to no information E. coli O157:H — 10 8 Cryptosporidium — 10 7

24 Fate of Salmonella in Cattle Manure Storage TemperatureDecimal Reduction Time ( o C) (Days) S. Himathongkham et al. FEMS Microbiol Lett 178:251 (1999)

25 Survival of E. coli O157:H7 in Bovine Feces Detected by enrichment 37 o C 22 o C  5 o C 

26 Survival of E. coli O157:H7 in Sheep Manure l Manure pile (7 m long by 3 m wide by 0.6 m deep) collected from sheep experimentally administered E. coli O157:H7; held undisturbed (not aerated) for 21 months s O157 isolated consistently for 12 months (except for November) from middle and bottom moist layers but not from dry feces at top u O157:H7 counts ranged from <10 2 to 2.2 x 10 6 cfu/g s O157 detected in 1 of 24 manure samples at 21 months I. T. Kudva et al. Appl. Environ. Microbiol. 64:3166 (1998)

27 E. coli O157:H7 Infection Associated with Well Water and Infected Cattle on a Dairy Farm l 16-month old child from dairy farm hospitalized with bloody diarrhea l E. coli O157:H7 isolated from: s Child's stool s 63% of cattle on the farm s Well water l Well water was contaminated with cattle manure S. G. Jackson et al., Epidemiol. Infect. 120:17, 1998

28 Lake-Associated Outbreak of E. coli O157:H7 Infection 1.12 cases of E. coli O157:H7 infection during June - July 1995 in Illinois 2.Acquired infection by swimming in a lake at an Illinois State Park -Case-control study revealed that risk for illness was associated with taking lake water into the mouth and swallowing lake water CDC, Morbid. Mortal. Weekly Rep. 45(21):437 (May 31, 1996)

29 Association of E. coli O157:H7 with Water l Drinking and recreational (swimming) waters have been identified as vehicles of E. coli O157 s Sources of contamination include: u Cattle manure seeping into well water or lakes u Children defecating in a lake and swimming pool

30 Survival of E. coli O157:H7 in Water l E. coli O157 can survive for a long period of time in water, especially at cold temperatures s Survival for more than 13 weeks in water at 8EC, with only a 10-to-100-fold reduction u Precautions should be taken when using lake or river waters for drinking or recreational purposes

31 Association of E. coli O157:H7 with Deer l During July - August 1997, 310 fresh deer fecal samples collected from ground at 5 Georgia wildlife management areas s No isolations of E. coli O157:H7 J. R. Fischer et al., University of Georgia

32 Association of E. coli O157:H7 with Deer l During autumn 1997, 371 fecal samples collected directly from hunter-killed deer at 6 Georgia wildlife management areas s E. coli O157:H7 isolated from 3 deer u All from deer in NW Georgia in vicinity of cattle u Two different PFGE DNA fingerprints J. R. Fischer et al., University of Georgia

33 Association of E. coli O157:H7 with Deer l During autumn 1998, 140 fecal samples collected directly from hunter-killed deer at NW Georgia location in vicinity of cattle s No isolations of E. coli O157:H7 l During same time period, 231 fecal samples collected directly from cattle present in vicinity of deer s E. coli O157:H7 isolated from 12 (5.2%) cattle J. R. Fischer et al., University of Georgia

34 Public Health Issues Associated Human Pathogens Carried by Animals 1.Contaminated food from animals l Meat, eggs, milk 2.Contaminated food that contacts animal waste l Vegetables and fruit grown in soil fertilized with animal manure or treated with irrigation water with animal waste 3.Contaminated water containing animal waste l Untreated drinking water and swimming in recreational lakes

35 Methods of Control for E. coli O157 l Low infectious dose of E. coli O157 necessitates reducing or eliminating pathogen, rather than solely preventing its growth l HACCP system most effective approach for reducing risk of E. coli O157 infections s Most desirable HACCP system includes a step that kills pathogens s For raw foods that do not receive a terminal kill treatment, HACCP systems must be implemented throughout food continuum, from farm to table

36 Where Must Food Safety Begin? l Solutions are complex but must begin at the farm l Food producers must consider and treat their products as foods rather than as commodities

37 Intervention or Control Points Food Producers Examples of CP’s for preharvest foods l Probiotics and competitive exclusion bacteria – Use of beneficial microorganisms that prevent colonization or eliminate pathogens from animals used for food products l Bacteriophage l Innovative vaccines l Dietary and feeding practices

38 Control of E. coli O157:H7 in Cattle by Competitive Exclusion Bacteria l Competitive exclusion involves use of microbial cultures that out-compete pathogens from colonizing specific niches s Principal sites of E. coli O157 localization in cattle are the animal’s three forestomachs and the large intestine s Isolates of E. coli that produce antimicrobials to E. coli O157 and localize in the same sites of bovine GI tract as E. coli O157 can eliminate or reduce carriage of E. coli O157 in ruminating calves

39 Recovery of E. coliO157:H7 at necropsy (13 to 27 days postinoculation) from experimentally infected calves No.Range Mean a Sample positive/ (CFU/gram) (CFU/gram) Site total contents contents Rumen9 / 9<0.5 X X X 10 2 Recticulum7 / 9<0.5 X X X 10 2 Omasum9 / 9<0.5 X X X 10 2 Abomasum0 / 9 00 Duodenum2 / 9 <0.5 X 10 1 <0.5 X 10 1 Ileum4 / 9<0.5 X X X 10 1 Distal cecum7 / 9<0.5 X X X 10 1 Spiral colon7 / 9<0.5 X X X 10 2 Descending 5 / 9<0.5 X X X 10 1 colon

40 Protocol l 20 adult steers (weight lbs) were fed production diet containing monensin (30g/ton) s Each administered by gavage E. coli O157 (5-strain mixture) at day 0 s 10 steers administered at 48 and 72 h post- challenge probiotic E. coli (3 strains) u E. coli O157 and probiotic bacteria fecal shedding monitored until day 33

41 E. coli O157:H7 (log CFU/g) in feces of cattle administered E. coli O157:H7 only

42 E. coli O157:H7 (log/g) at necropsy (day 33) in cattle administered E. coli O157:H7 only Steer No. Rumen content Rumen tissue Colon content Colon tissue Feces < < < < < < < < < < < <1.1

43 E. coli O157:H7 (log/g) in feces of cattle administered E. coli O157:H7 and probiotic bacteria Steer No. Day 2Day 12Day 21Day <1.1 < <2.4 <1.1 <2.4 <1.1 <2.4 <1.1

44 E. coli O157:H7 (log/g) at necropsy (day 33) in cattle administered E. coli O157:H7 and probiotic bacteria Steer No. Rumen content Rumen tissue Colon content Colon tissueFeces < < <1.1 <2.4 <1.1 <2.4 <1.1 <2.4 <1.1

45 Bacteriophage Treatment of E. coli O157:H7 Infection of Calves l Six bacteriophage (10 11 pfu) capable of lysing most E. coli O157:H7 strains were orally administered at -7, -6, 0 and 1 day to 6-week old calves (5 per group) per orally administered 3x10 9 E. coli O157:H7 on day 0 s Phage-treated calves shed fewer E. coli O157 on day 2, 4 and 6 than calves fed E. coli O157 only, and E. coli O157 was not shed after day 8 s 4 of 5 calves fed E. coli O157 shed O157 for 10 to 16 days T. Waddell et al. Abstr. VTEC 2000, No. 179 (2000)

46 Control of E. coli O157:H7 in Cattle by Vaccination l Vaccination involves exposing animal to attenuated pathogen or antigen of a virulent microorganism to produce immunity s Traditional approaches to vaccinate cattle against E. coli O157 are not likely to be successful s Innovative vaccines may be useful u Example, insert genes of virulence factors of E. coli O157 into alfalfa to stimulate production of IgA in GI tract

47 Edible Vaccine in Potatoes l Potatoes were genetically engineered to produce B subunit of E. coli heat labile enterotoxin s Results of volunteers who ingested transgenic potatoes: u 10 of 11 had a 4-fold increase in serum (IgG) antibodies u 6 of 11 had a 4-fold increase in intestinal (IgA) antibodies

48 Control of E. coli O157:H7 in Cattle by Farm Management Practices l Water troughs are on-farm sources of E. coli O157 contamination from cattle manure and cud s Need frequent cleaning of water troughs and improved design of cattle water reservoirs to reduce contamination

49 Effect of Diet on Carriage of E. coli O157:H7 by Cattle l Eight 1- to 2-year-old Holstein steers were fed finishing diets of 82 to 90% grain (barley/corn), 100% alfalfa hay or 100% timothy grass (modified crossover design) l Administered E. coli O157:H7 via gastric tube into rumen to each steer 3 weeks after adaption to a particular diet C. J. Hovde et al. Appl. Environ. Microbiol. 65:3233 (1999)

50 Effect of Diet on Carriage of E. coli O157:H7 by Cattle l Average duration of fecal shedding of E. coli O157:H7: Grain diet 4 days Alfalfa diet39 days Timothy grass diet42 days l Acid resistance of E. coli O157:H7 was unaffected by diets C. J. Hovde et al. Appl. Environ. Microbiol. 65:3233(1999)

51 Influence of Feed Rations on Fecal Shedding of Shiga Toxin-Producing E. coli by Cattle l Cattle were fed rations of grain or hay in 2- to 3-week increments or solely grain or hay s Irrespective of the feeding regime, STEC excretion was significantly reduced during the first week after changing the feed u Thereafter, STEC fecal excretion increased s STEC isolates from feces possessed high acid tolerance which was not influenced by feeding regime H. Richter et al. Abstr. Shiga Toxin-Producing E. Coli 2000, No. 8 (2000)

52 Approach to Addressing Foodborne Pathogens on the Farm 1.Prioritize foodborne pathogens of greatest concern in livestock and poultry 2.Identify vehicles of transmission of specific foodborne pathogens in production environment 3.Identify points of intervention that will have the greatest impact on reducing the occurrence of foodborne pathogens at production

53 Approach to Addressing Foodborne Pathogens on the Farm 4.Develop practical and effective intervention strategies that will reduce or eliminate selected foodborne pathogens from principal animal source 5.Develop Good Agricultural Practices for producing livestock and poultry

54 Prioritize Foodborne Pathogens of Greatest Concern in Livestock and Poultry l Epidemiologic case-control studies of human illness indicate strong correlations with: Human DiseasePrincipal Risk Factors E. coli O157:H7 infections- Eating undercooked ground beef - Visiting a farm - Contact with cattle Campylobacter infections- Handling raw poultry - Eating undercooked poultry Salmonella enteritidis - Eating uncooked or lightly infections heated egg products

55 Potential Vehicles of Transmission of Foodborne Pathogens in the Production Environment l Manure l Drinking water l Feed l Environment l Rodents, insects, wildlife

56 What Points of Intervention Will Have Greatest Impact on Reducing Occurrence of Foodborne Pathogens at Production l Case-control studies to identify major risk factors associated with occurrence/transmission of foodborne pathogens at production

57 Case-Control Study of E. coli O157:H7 Fecal Shedding in Dairy Calves 1.Determined that calves are more likely to shed E. coli O157:H7 after weaning (4.8%) than before weaning (1.4%) 2.Shedding in calves was associated with: a.Grouping calves before weaning b.Sharing buckets and bottles among unweaned calves without washing or rinsing c.Feeding grain to calves less than 5 days old

58 Case-Control Study of E. coli O157:H7 Fecal Shedding in Dairy Calves 3.Shedding was negatively associated with: a.Feeding calves whole cottonseed b.Pasturing in clover Garber et al JAVMA 207:46-49.

59 Possible Intervention Strategies to Reduce Pathogens at Production in Livestock and Poultry l Probiotics/competitive exclusion bacteria l Bacteriophage l Innovative vaccines l Genetically modified feeds (e.g., introduce antimicrobials into grain) l Genetically modified animals resistant to colonization by pathogens l Modify farm management practices l Manure treatment

60 Example of Approach to Reduce E. coli O157:H7 On Farm

61 Example of Approach to Reduce E. coli O157:H7 at Farm l Principal contributing factor to human illness is exposure to cattle feces based on principal risk factors (eating undercooked ground beef, visiting a farm, contact with cattle)

62 Example of Approach to Reduce E. coli O157:H7 at Farm l Principal points of intervention to reduce human exposure: s Reduce/eliminate intestinal carriage and fecal shedding of E. coli O157 s Reduce contamination of drinking water vessels used by cattle s Reduce E. coli O157 contamination of manure in the farm environment s Good personal hygiene of animal handlers

63 Example of Approach to Reduce E. coli O157:H7 at Farm l Develop practical and effective intervention strategies such as: s Reduce intestinal carriage and fecal shedding by: u Competitive exclusion bacteria u Innovative vaccines u Bacteriophage u Farm management practices

64 Example of Approach to Reduce E. coli O157:H7 at Farm l Develop practical and effective intervention strategies such as: s Reduce contamination of drinking water vessels u Redesign vessels that remove cud sediment u Cleaning regimes to remove biofilms that entrap E. coli O157

65 Example of Approach to Reduce E. coli O157:H7 at Farm l Develop practical and effective intervention strategies such as: s Reduce contamination of manure in farm environment u Develop biological competitive approaches to kill E. coli O157 in manure in farm yard u Develop methods to kill E. coli O157 in cow manure- based compost u Develop farm management practices for manure application to soil to reduce E. coli O157 contamination of produce and feeds

66 Example of Approach to Reduce E. coli O157:H7 at Farm l Develop practical and effective intervention strategies such as: s Educate animal handlers in good personal hygiene u Hand washing u Avoid touching mouth u CDC guidelines s Farm visitors avoid contact with animals and manure u Use good personal hygiene u CDC guidelines

67 Example of Approach to Reduce E. coli O157:H7 at Farm l Develop Good Agricultural Practices for producing cattle s Need to identify control points and intervention treatments s Prepare GAP guidelines for control food safety aspects of beef cattle production

68 Program Needs 1.Develop Good Agricultural Practices for livestock and poultry production –Should include input of experts in food safety with experience in animal production

69 Program Needs 2.Develop HACCP/GAPs for composting/manure treatment –Should include input of experts in food safety with experience in animal waste handling

70 Program Needs 3.Research program (case-control studies) to identify principal risk factors associated with transmission of target pathogens in livestock and poultry production

71 Program Needs 4.Research program to develop effective intervention strategies to: a.Reduce carriage/fecal shedding of pathogens by livestock and poultry ● EHEC 0157:H7 - Cattle ● Campylobacter - Poultry, Cattle ● Salmonella - Poultry, Swine, Cattle ● Cryptosporidium - Cattle b.Treat manure to kill pathogens before used for soil application, or contaminates irrigation or processing water

72 Program Needs 5.Develop educational program for producers/farmers ● Should include involvement of: a.Extension Service at Land Grant Universities b.Veterinary Schools/Veterinarians c.Veterinary Pharmaceutical Companies d.Representatives of food service, food retail and food processing industries e.Public relations firm to simplify messages and present them for effective communication


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