FOODBORNE ZOONOSES

1. FOODBORNE ZOONOSES • Over 250 diseases can be caused by contaminated food or drink • most are bacterial (Salmonella and Campylobacter) or caused by Norwalk virus • most cases are single cases, not associated with a recognized food-borne outbreak • majority of food items are raw or undercooked products of animal origin (meat, dairy, poulty, seafood) • ~ 500 outbreaks reported each year

2. FOODBORNE ZOONOSES • Foodborne illness a substantial problem in US • 6.5 to 33 milliion cases annually • ~9000 deaths • Since 1986, of ~3200 outbreaks reported, only 21 were associated with contaminated produce • Reporting of food- and water-borne diseases began over 50 years ago as investigations of enteric fevers

3. FOODBORNE ZOONOSES

4. FOODBORNE ZOONOSES • Major virulence determinants: • toxins - destroy, damage, inactivate natural defense mechanism of host • exotoxins • endotoxins • enzymes - assist bacteria in establishing infection and producing disease

5. FOODBORNE ZOONOSES Toxins • exotoxins • secreted from cell or leak out after cell death • soluble protein, thus readily carried through body by lymphatics or blood • damage at distant site, usually specific • normally destroyed by heating to 100º C., although some are resistant to boiling (S. aureus) • non-pyrogenic • example: botulinism toxin, Staphylococcus aureus

6. FOODBORNE ZOONOSES Toxins • endotoxins • produced only by gram negative bacteria • part of the outer cell wall (lipopolysaccharide coat) • lipid A component is toxic • side chains (O, H antigen) are immunogenic • released in large amounts at cell death • heat stable, not destroyed by autoclaving • less potent and less specific than exotoxins

7. FOODBORNE ZOONOSES Toxins • endotoxins • pyrogenic • toxic to most animals, producing similar range of biological effects regardless of source • fever • increased WBC • DIC (disseminate intravascular coagulopathy) • hypotension • shock • death • degraded by oxidizing agents • examples: E. coli, Salmonella, Shigella

8. FOODBORNE ZOONOSES Enzymes • spreading factors • hyaluronidase (gram +) - attacks interstitial cement of connective tissue • collagenase (Clostridium) - break down collagen, facilitating invasion of muscle and gas gangrene formation • neuraminidase (Vibrio and Shigella) - break down intercellular cement of intestinal epithelial cells • kinase (Strep and Staph) - digests fibrin, preventing clotting and allowing rapid diffusion

9. FOODBORNE ZOONOSES Enzymes • cell lysis • hemolysins (Staph, Strep, and Clostridia) • lecithinases (C. perfringens) • phospholipases (C. perfringens) -  toxin • coagulase (Staph) - causes clotting • adenylate cyclase activity - bacterial toxins having immediate (short-range) effects that promote invasion • Ex: anthrax toxin - edema factor

10. FOODBORNE ZOONOSES New challenges • newly identified pathogens (emerging pathogens) • newly identified vehicles of transmission • changes in food production • changes in food distribution • decline in food safety awareness

11. FOODBORNE ZOONOSES Reasons for emergence or re-emergence • changes in pathogen • centralized and concentrated production • globalization of food supply • increase in “at risk” populations • changes in food animal practices • changes in type and volume of foods imported • now import over 30 billion tons of food annually • change in dietary preferences and exposure has led to many more types of produce being introduced

12. FOODBORNE ZOONOSES Surveillance programs • Foodborne Disease Active Surveillance Network (FoodNet) by CDC-EIP • collaboration with USDA, FDA • to determine incidence of foodborne illness in US • established in 7 locations: • California (selected counties) • Connecticut (selected counties) • Georgia (selected counties) • Minnesota (entire state) • Oregon (entire state) • New York (selected counties) • Maryland (selected counties)

13. FOODBORNE ZOONOSES Surveillance programs • FoodNet (continued) • to document effectiveness of Hazard Analysis and Critical Control Points Rule (HACCP) • active surveillance • population survey • physician survey • case-control study of E. coli O157:H7

14. FOODBORNE ZOONOSES Surveillance programs • Antimicrobial resistance surveillance • PulseNet - network set up for molecular subtyping • pulsed-field gel electrophoresis method for E. coli O157:H7 now available in 24 state laboratories, along with USDA and FDA • rapid comparison of PFGE profiles with database at CDC • already been critical in outbreak investigation in Colorado associated with ground beef and multi-state investigation traced to alfalfa sprouts • Basic research at NIH • establish virulence mechanisms and develop prevention tools

15. FOODBORNE ZOONOSES Surveillance programs • Enter-Net (formerly Salm-Net) • European Commission funded • Established for surveillance for Salmonella and E. coli infections • Includes 15 European countries • has already let to public health interventions and product recalls in Europe

16. FOODBORNE ZOONOSES • Escherichia coli O157:H7 • Campylobacter spp. (jejuni; fetus ssp. fetus) • Listeria monocytogenes • Salmonella spp. (Enteriditis; Typhimurium) • Yersinia enterocolitica; Y pseudotuberculosis

17. Escherichia coli • gram-negative rod-shaped bacteria • hundreds of strains • most strains are harmless, normal intestinal flora of healthy humans and animals • occurrence: ubiquitous, worldwide distribution

18. Categories of Escherichia coli causing diarrhea • enterohemorrhagic (EHEC - hemorrhagic colitis; O157:H7) • enterotoxigenic (ETEC- traveler’s diarrhea) • enteroinvasive (EIEC - dysentery-like) • enteropathogenic (EPEC - infant diarrhea) • enteroaggregative (infant d. in underdeveloped countries) • diffuse-adherence (pediatric diarrhea)

19. Escherichia coli O157:H7 • first recognized in 1982 outbreak of hemorrhagic diarrhea traced to hamburgers (fast food chain) • estimated 10,000 to 20,000 cases/yr in the US • outbreaks have been associated with other foods such as leaf lettuce, cider, contaminated water • more commonly isolated than Shigella

20. Escherichia coli O157:H7 • “O” and “H” designation refer to cell surface antigen markers that are used to distinguish serotypes • Other serotypes of enterohemorrhagic strains may also be implicated (O26:H11; O111:H8; O104:H21)

21. Escherichia coli O157:H7 • syndrome caused by potent cytotoxins: verotoxins 1 and 2 (Shiga-like toxins I and II because resemble toxins of Shigella dysenteriae) • may also produce hemolytic-uremic syndrome • although recognized and intensively studied for 15 years, still do not know best method of treatment nor how animals become infected

22. Escherichia coli O157:H7 • Microbiological features and identification • most enterohemorrhagic (EHEC) strains of E. coli do not ferment sorbitol (MacConkey-sorbitol media used for screening O157:H7) • presence of Shiga-like toxins • serotyping (phage typing)

23. Escherichia coli O157:H7 • Microbiological features and identification • identification of toxin genes by DNA probes • presence of virulence plasmid (plasmid allows expression of a fimbria, attachment to the intestinal mucosa) • does not grow well or at all at 44-45ºC

24. Escherichia coli O157:H7 Epidemiological features • Reservoir: • cattle especially young dairy cattle • wild ruminants - deer (?) • humans

25. Escherichia coli O157:H7 Epidemiological features • Transmission: • ingestion of contaminated foods • usually inadequately cooked beef (especially ground beef) • raw milk • other foods by cross-contamination--lettuce, apple cider, apple juice • person-person (families, child care facilities, institutions) • waterborne (swimming in crowded areas, drinking water)

26. Escherichia coli O157:H7 Epidemiological features • Incubation period: • relatively long, ranging from 3-8 days • Period of communicability: • <1 week in adults • may be up to three weeks in children • prolonged carriers uncommon

27. Escherichia coli O157:H7 Epidemiological features • Susceptibility and resistance • very low infectious dose • old-age appears to be a risk factor • children < 5 years of age are at greatest risk of developing hemolytic-uremic syndrome

28. Escherichia coli O157:H7 Epidemiological features • Occurrence • important cause of foodborne disease in US, UK, Europe, Japan, South Africa, southern regions of South America, Australia • importance in underdeveloped regions and rest of world not established

29. Escherichia coli O157:H7 Clinical features • diarrhea ranging from mild, non-bloody to virtually • straight bloody stool, abdominal cramping • fever is infrequent

30. Escherichia coli O157:H7 Clinical features • Hemolytic-uremia syndrome • more common in children • may occur in up to 10% of cases • characterized by: • hemolytic anemia • thrombocytopenia • renal failure (common cause of renal failure in children)

31. Escherichia coli O157:H7 Clinical features • Thrombotic thrombocytopenic purpura (TTP) in elderly • Case fatality rate: 3-5% (up to 50% in elderly with TTP)

32. Escherichia coli O157:H7 Control methods • Preventive measures to reduce incidence • slaughterhouse management to minimize contamination of meat by intestinal contents • pasteurization of milk and dairy products • irradiate beef, especially ground beef

33. Escherichia coli O157:H7 Control methods • preventive measures to reduce incidence • adequately cook meat to a temp of 155°F (68°C) • ‘pink all gone’ does not mean necessarily safe - cooking with meat thermometer is recommended • protect, purify, chlorinate public water supplies for drinking • chlorination of swimming pools • adequate hygiene in day-care facilities

34. Escherichia coli O157:H7 Control methods • control of patient and immediate environment • report to health department (mandatory in many states) • isolation: because of extremely small infective dose, patients should not be allowed to handle food or provide child/patient care until 2 negative samples are obtained • disinfection • contacts with diarrhea should be handled as if infected (no food handling, no patient care or child contact) until two negative fecal samples are obtained

35. Escherichia coli O157:H7 Control methods • treatment • fluid/electrolyte replacement • antibiotic treatment uncertain; TMP-SMX may lead to hemolytic-uremia syndrome

36. Campylobacter enteritis Background • Significant cause of enteritis worldwide and of traveler’s diarrhea in U.S. • Leading cause of bacterial diarrhea in U.S. • Campylobacter 45% • Salmonella 30% • Shigella 17% • E.coli O157:H7 5% • Most common isolate: C. jejuni (C. fetus ssp. jejuni)

37. Campylobacter enteritis Microbiology • Campylobacter jejuni; C. colio, C. fetus ssp. fetus, C. spp. • many biotypesand serotypes occur; useful in epidemiology • gram-negative, microaerophillic, motile rods • distinct shape of organism, flagella useful in identification • require special environmental conditions for optimal growth • 5% O2 • prefers relatively high concentration of CO2 • relatively fragile, sensitive to stresses such as oxygen, drying, heat, acidic conditions

38. Campylobacter enteritis Microbiology Gram stain from culture media (Note slender, curved rods)

39. Campylobacter enteritis Clinical features • watery diarrhea, sometimes with blood (occult) • normally self-limiting, not requiring treatment • most common in children (<5 yrs) and young adults (15-29 yrs of age) • low fatality rate--usually in immunocompromised • infective dose small (~500 organisms in some cases) • toxin production may cause diarrhea

40. Campylobacter enteritis Epidemiology • Occurrence: estimated 2 - 4,000,000 cases/yr in US, probably more • Reservoir: • poultry and cattle primarily; also pets, swine, and other species • common contaminant of raw poultry (20-100% at retail) • can exist in intestinal tract of people and animals without causing symptoms • present in high numbers in stools of infected symptomatic individuals

41. Campylobacter enteritis Epidemiology • Mode of transmission: • vehicles: • undercooked meat • contaminated food and water • raw milk • direct contact: pets, farm animals, infected infants • person-person uncommon

42. Campylobacter enteritis Prevention and control • On the farm: good sanitary practices (USDA guidelines) • In the plant: HACCP1 to minimize opportunity for spread • At retail: recall policy on ready-to-eat meat and poultry products found to be contaminated enforced by USDA (similar for E. coli O157:H7) • Consumer: proper food handling procedures in kitchen 1 HACCP = Hazard Analysis and Critical Control Point

43. Campylobacter enteritis Prevention and control • CDC report: 80% of US outbreaks due to Campylobacter could be prevented with universal pasteurization of milk and proper treatment of drinking water • improved handling of chicken important • bacteria destroyed when meat/poultry reach internal temperature of 160º F • freezing not reliable method for destroying organism but thorough cooking will render product safe

44. Campylobacter enteritis Outbreaks • Usually outbreaks are small (< 50 individuals) • Vermont: 2,000 people ill from temporary use of non-chlorinated water supply • 1986 outbreak in school children traced back to milk which was being pasteurized for 135º F for 25 minutes rather than the required 145º F for 30 minutes (LTLT) • Note: 161º F for 15 seconds (HTST) 280º F for 2 seconds (ultra-pasteurized)

45. SALMONELLOSIS • Causative organisms: primarily S. enteriditis, typhimurium in U.S. • numerous serotypes, many are pathogenic to both animals and man • of the ~2,000 serotypes known, only ~200 recognized in the U.S. • discovered in 1880, genus named for American scientist Salmon in honor of his extensive work

46. SALMONELLOSIS • Microbiological features and identification • gram-negative rod-shaped bacteria • motile (non-motile forms are S. gallinarium, pullorum) • heat labile • growth prevented at <7º C for most serotypes • non-spore forming, but can survive for long periods in foods and other substrates • can survive for long periods in foods with low aw (water activity) such as chocolate, peanut butter, black pepper)

47. SALMONELLOSIS Epidemiology - reservoir • ubiquitous • found in a wide range of animals, particularly poultry, swine, cattle, pets (iguanas, turtles, terrapins, tortoises, chicks, dogs, cats), humans • chronic carriers common in animals and birds, less so in humans • S. enteriditis infects ovaries of healthy appearing hens, thereby contaminating eggs in oviduct before shell is formed

48. SALMONELLOSIS Epidemiology - reservoir • S. typhi, paratyphi - man only • S. typhimurium - animals, particularly food animals • S. enteriditis - animals, particularly food animals • S. dublin - cattle • S. choleraesuis - swine • S. gallinarum, pullorum - poultry • S. arizonae - animals, reptiles

49. SALMONELLOSIS Epidemiology - mode of transmission • ingestion of raw, undercooked, or contaminated food • meat, milk, eggs, produce • fecal-oral transmission • contact with pets (especially infants) • foods contaminated by infected food handler • outbreaks usually traced to food items

50. SALMONELLOSIS Epidemiology - disease frequency • incidence highest in infants and young children • estimated 5 million cases annually (US) • up to 80% are sporadic cases • large outbreaks in hospitals, restaurants, institutions are common • largest outbreak in US (25,000 cases) resulted from a nonchlorinated municipal water supply