2 Foodborne viruses - FOODBORNE VIRUSES Dr Ryser FSC 342...

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Unformatted text preview: FOODBORNE VIRUSES Dr. Ryser FSC 342 NOROVIRUS STRIKES LANSING! FOODBORNE VIRUSES Introduction Structure Small obligate intracellular parasites Contain either RNA or DNA (single or double stranded) surrounded by a protective virus-encoded protein coat Virus Structure – Hepatitis and Norovirus Foodborne viruses transmitted as particles measuring 25- 75 nm in diameter VIRUS STRUCTURE - Bacteriophage Protein Capsid (contains DNA) Collar Tube Contractile Sheath (covers tube) Tail Tail Fibers End Plate VIRUS MULTIPLICATION Attachment of viral protein to a specific receptor on cell surface Penetration of host cell membrane Un-coating of virus leaving nucleic acid Replication- of viral proteins by the host RNA Duplication FOODBORNE VIRUSES: Steps in Viral Gastroenteritis Ingest the virus Survives harsh stomach conditions Invades and multiply in epithelial cells of the small intestine Shed in feces FOODBORNE VIRUSES Two viruses among top 10 causes of foodborne illness Hepatitis A Norovirus (formerly Norwalk virus) FOODBORNE VIRUSES Viral gastroenteritis most common foodborne illness in Minnesota from 1984 - 1991 (poor hygiene and infected food handlers) Before 1999 most foodborne gastroenteritis was assumed to be bacterial Norovirus is now responsible for about two-thirds of all foodborne gastroenteritis cases 4 FOODBORNE VIRUSES Totally inert- unable to replicate outside host cell (i.e. food, water or the environment) Environmentally Stable- resistant to many common methods used to inactivate bacteria Notably low infectious dose FOODBORNE VIRUSES: Enteric Viruses Hepatitis A and Norovirus Transmission: oral Food or water: shed in feces Person-to-person Most infections detected as outbreaks FOODBORNE VIRUSES: Enteric Viruses Human generally the exclusive host with animal vectors not involved (exception: tick-borne encephalitis) Principal sites of action following ingestion Small intestine - Norovirus Liver – Hepatits A FOODBORNE VIRUSES: Enteric Viruses Infectious dose Theoretically 1 particle but unlikely Fecal shedding: >108 particles/g 10 ug of fecal contamination (1,000 particles) is highly infectious Almost impossible to detect this level of contamination in 100 g of food Hepatitis Virus Classification Types A, B, C, D and E – All infect the liver Types A and E transmitted by fecal- oral route Type A: Virtually Worldwide Type E: primarily Asia, Africa, Latin America Hepatitis A Virus Shape / Size Spherical 28 - 32 nm Survival Dried feces – 1 month pH 1.0 / 38°C - 90 minutes Hepatitis A Virus Inactivation Milk: complete elimination by HTST pasteurization questionable Relatively resistant to: Chlorine – 1: 10 dilution of household bleach/1 minute required due to organics (feces)] (less resistant in water) Gamma radiation Hepatitis: The Disease Susceptible Population everyone Greatest risk Children < age 5 in developing countries (most exposed and have acquired active immunity) Adults (developing countries) Cirrhosis of liver Immune status less important Hepatitis: The Disease Hepatitis E More serious in pregnant women (17 - 33% mortality) Hepatitis:The Disease Hepatitis A indistinguishable from Hepatitis E More common in children than type E Frequently asymptomatic in young children as opposed to adolescents and adults Hepatitis A: Transmission Contaminated food/ water North America: Salads and fruits via food handlers Worldwide: Contaminated shellfish Person-to-person Regular contact Sexual contact Daycare centers Hepatitis A: Infection Ingest virus through food or water Survives passage through the stomach Infects intestinal cells Moves to the liver Does not kill cells Immune response destroys infected cells Excreted in bile and then feces Shed in high number 10- 14 days before symptoms Hepatitis: Incubation Period Hepatitis A 15-50 d (28 - 30 d) fecal shedding 10-14d before onset Shedding 7-14 d after onset leads to food transmission Hepatitis E 22 - 60 d (40 d) Hepatitis: Symptoms and Diagnosis Symptoms: Jaundice, anorexia, vomiting and profound malaise Death is rare Diagnosis Demonstration of antibodies against virus in blood commercial test kits Hepatitis: Outbreaks Outbreaks Hundreds reported since first outbreak in 1943 Earlier United States estimate: 4,800 35,000 cases of foodborne hepatitis A annually 1999: Estimate of 4,170 foodborne cases Hepatitis: Incidence Hepatitis: Outbreaks Reported risk factors among persons with hepatitis A, United States, 1990–2000. IDU, injection drug use; MSM, men who have sex with men. Hepatitis: Vehicles of infection Water, raw shellfish, fruits and vegetables, salads Luncheon meats Sandwiches Fruit Juices and iced drinks Milk and dairy products Hepatitis: Sources of Contamination Water (shellfish) Infected workers Food processing facilities Restaurants Retail Hepatitis: Outbreaks Foods contaminated by infected handler 1962 Missouri: 28 cases - Reconstituted orange juice 1978 Arkansas/Texas: 140 cases - Vegetarian sandwiches and salads 1986 Florida: >100 cases - Floating restaurant 1988 Shanghai: 310,746 cases - Shellfish 1988 Kentucky: >200 cases - Lettuce (unknown origin) 1989 England: 50 cases - bakery 1990 Missouri: 110 cases - lettuce 1998 Maryland: hepatitis A carrier prepared salad bar at Wendy's (an estimated 3000 people served) Hepatitis A from Frozen Mexican Strawberries via California - 1997 The Outbreak The beginning of March 1997 saw the outbreak of approximately 260 cases of Hepatitis A in Calhoun County, Michigan. This epidemic has startled national health officials, since an outbreak of this magnitude has not occurred in the United States in over ten years. In an effort to determine the origins of the Hepatitis A epidemic, the Centers for Disease Control and the United States Department of Agriculture quickly dispatched investigators to Michigan. Investigators found a positive link between strawberries served in a local cafeteria and the Hepatitis A outbreak. the majority of those infected with the disease were understandably children. The strawberries served in the school lunches were traced to a processing plant in San Diego, known as Andrew and Williamson. It was discovered that this processing company shipped strawberries from the same lot as the ones sent to Michigan to schools in five other states, including Arizona, southern California, Georgia, Iowa, and Tennessee. As a precautionary measure, the CDC and school officials in these states set up immunization programs for students with shots of immune globulin to protect students that may have been infected. A Multistate, Foodborne Outbreak of Hepatitis A Yvan J.F. Hutin, M.D., Vitali Pool, M.D., Elaine H. Cramer, M.D., Omana V. Nainan, Ph.D., Jo Weth, M.A., Ian T. Williams, Ph.D., Susan T. Goldstein, M.D., Kathleen F. Gensheimer, M.D., Beth P. Bell, M.D., Craig N. Shapiro, M.D., Miriam J. Alter, Ph.D., Harold S. Margolis, M.D., for The National Hepatitis A Investigation Team ABSTRACT Background We investigated a large, foodborne outbreak of hepatitis A that occurred in February and March 1997 in Michigan and then extended the investigation to determine whether it was related to sporadic cases reported in other states among persons who had consumed frozen strawberries, the food suspected of causing the outbreak. Methods The cases of hepatitis A were serologically confirmed. Epidemiologic studies were conducted in the two states with sufficient numbers of cases, Michigan and Maine. Hepatitis A virus RNA detected in clinical specimens was sequenced to determine the relatedness of the virus from outbreak-related cases and other cases. Results A total of 213 cases of hepatitis A were reported from 23 schools in Michigan and 29 cases from 13 schools in Maine, with the median rate of attack ranging from 0.2 to 14 percent. Hepatitis A was associated with the consumption of frozen strawberries in a case–control study (odds ratio for the disease, 8.3; 95 percent confidence interval, 2.1 to 33) and a cohort study (relative risk of infection, 7.5; 95 percent confidence interval, 1.1 to 53) in Michigan and in a case– control study in Maine (odds ratio for infection, 3.4; 95 percent confidence interval, 1.0 to 14). The genetic sequences of viruses from 126 patients in Michigan and Maine were identical to one another and to those from 5 patients in Wisconsin and 7 patients in Arizona, all of whom attended schools where frozen strawberries from the same processor had been served, and to those in 2 patients from Louisiana, both of whom had consumed commercially prepared products containing frozen strawberries from the same processor. Distribution of Frozen Strawberries The strawberries implicated in this outbreak were grown in Mexico, processed and frozen in a California plant, and distributed through the Department of Agriculture for school-lunch programs and through distributors for commercial use. The processor shipped 13 lots of frozen strawberries processed on April 19, May 8, and May 9, 1996, to the Michigan school-lunch programs, and 9 lots processed on April 29, April 30, and May 3, 1996, to the Maine school-lunch programs. In each state, the sealed 30-lb (14-kg) containers of frozen strawberries were opened in the school kitchens, thawed, and incorporated into shortcakes or served in cups. The risk of illness associated with specific lot numbers could not be examined because no records were kept of which local kitchens received which lots. Officials of the California Department of Health Services, the Food and Drug Administration (FDA), and the Department of Agriculture surveyed the plant where the strawberries had been processed, packed, and frozen. The investigation did not identify any record of illness consistent with hepatitis A among the employees during the time the strawberries were processed. Strawberries were carried on a conveyor belt, washed in a chlorine solution of 12 parts per million, mechanically sliced, combined with a sucrose solution, packed, and frozen. Hand contact with the berries was limited to the rejection of unacceptable berries as they passed on the conveyor belt. Officials from the FDA also visited three of the four growing fields in Mexico. Water for drip irrigation was piped from a river and filtered in sand tanks. Few slit latrines were available for use by pickers. The only hand-washing facilities were on trucks that circulated through the fields. The pickers did not wear gloves and removed the strawberry stems with their fingernails. No records were kept of illnesses among the picker Attorney for Hepatitis victims cautions against assuming green onions are source of hepatitis outbreak Seattle Attorney also renews call on Chi-Chi’s to compensate victims of hepatitis outbreak, repay Department of Health for shot administration and outbreak investigation PITTSBURGH (November 18, 2004) — Seattle attorney William Marler today cautioned consumers against attributing the current outbreak of hepatitis-A in Pennsylvania to consumption of green onions. Marler again called on Chi Chi’s to pay damages to those 8,000 people exposed to, and 500 people infected with, hepatitis-A after eating at the restaurant’s Beaver Valley Mall location in October and early November. Marler represents nearly 50 people sickened and exposed in the outbreak. His law firm, Marler Clark, along with the Pittsburgh law firm of Meyers, Rosen, Louik, and Perry, has already filed three lawsuits against Chi Chi’s. Hepatitis Outbreaks: 2002 – 2004 2004 2003 Hepatitis: Treatment and Prevention Prevention Human immune serum globulin (positive immunity) Vaccine: Hepatitis A NOROVIRUS Responsible for 66% of all foodborne gastroenteritis cases in the United States ~9.2 million cases annually Easily transmitted Drastically under reported 4 NOROVIRUS: Characteristics Unable to multiply in any laboratory host (cant culture) “Small, round, structured viruses" (SRSVs) ~30 - 38 nm in diameter Single strand of RNA NOROVIRUS: Stability Determined from human feeding studies remains infectious after refrigeration and freezing pH 2.7/room temperature: 3 hours Survives in fermented, brined and pickled foods NOROVIRUS: Stability Temperature Remains infectious after refrigeration and freezing 60°C/pH 7 for 1 hour Generally inactivated in properly cooked foods Environment Survives well on inanimate surfaces NOROVIRUS: Inactivation 1000 ppm Phenolic compounds Hydrogen peroxide Heat: 70 C NOROVIRUS: Detection Historically complicated by virus concentration and testing methods Concentration – extraction, filtration, absorption/elution, centrifugation (yield: 10-90%) NOROVIRUS: Detection Traditional: Cell Culture (primate kidney cells) Problems: low levels in food (1 - 200 viruses / g in shellfish), interfering food components, poor replication or no replication (norovirus) Emerging methods: ELISA and DNA/RNA probes, PCR NOROVIRUS: Transmission Foodborne Food handlers Source: harvesting, processing, packing, transport Water Wells, recreational water Low chlorination Person-to-person Fecal-oral High rate of secondary transmission Low ID NOROVIRUS: Susceptible Population Widespread susceptibility attack rate typically >50% -Most people exposed will have symptoms 50% of United States children exposed by age 6 Antibodies to virus do not afford protection vaccine not promising NOROVIRUS: Symptoms Incubation period: 6-48 hours Abrupt onset: nausea, vomiting, diarrhea More vomiting in children Duration: 12- 72 h Virus shed in vomit and up to 1 week in feces after symptoms end No long term complications NOROVIRUS: Diagnosis Detection of viral antibody in serum/ blood Detection of virus particles in stool by electron microscopy, immune electron microscopy NOROVIRUS: Outbreaks Restaurants and delicatessens (~60%) Cruise ships Nursing homes Other Schools Camps Prisons Private homes NOROVIRUS: Implicated Foods Fresh fruits and vegetables- lettus and salad bars Sandwiches Seafood- oysters Baked goods- cakes Meats Ice (resistant to freezing) NOROVIRUS: Shellfish Outbreaks Outbreaks Shellfish (frequent vehicles) First Outbreak - Oysters: >2,000 cases, attack rate 85% (1978 Australia) Depuration of shellfish Persists longer than fecal coliforms NOROVIRUS: Other Outbreaks Butter cream frosting: ~3,000 cases (Minneapolis / St. Paul, MN,1982) Ice: ~5,000 cases (Pennsylvania and – Delaware, 1982), 200 cases (Hawaiian cruise ship, 1992) School lunches: 3,353 cases (Japan 1991) Fresh cut fruit: 238 cases (Hawaiian cruise ship, 1990) NOROVIRUS: 2004 Outbreaks NOROVIRUS: 2004 Outbreaks NOROVIRUS: 2004 Outbreaks NOROVIRUS: 2004 Outbreaks NOROVIRUS: 2004 Outbreaks NOROVIRUS: 2004 Outbreaks NOROVIRUS: 2004 Outbreaks NOROVIRUS: Outbreaks January 2002 – January 2003 OTHER FOODBORNE VIRUSES Astrovirus Rotavirus 4 ASTROVIRUS Small (approximately 28nm diameter) circular, sometimes showing a starshaped surface configuration *Responsible for gastroenteritis especially in small children ASTROVIRUS Astrovirus infections occur most often during the cooler months of the year (October to April) Causes infantile gastroenteritis, but older children and adults can also be affected Foodborne outbreaks are rare ROTAVIRUS Exhibits a characteristic wheel-like appearance when viewed by electron microscopy (Latin rota, meaning "wheel"). The virus is stable in the environment. ROTAVIRUS The most common cause of severe diarrhea among children in the US 55,000 hospitalizations annually Worldwide ~600,000 fatalities in children annually Symptoms: Incubation period:~2 days Vomiting and watery diarrhea for 3 - 8 days fever and abdominal pain ROTAVIRUS: Transmission Fecal- oral route Contaminated water or food More common during the cooler months Foodborne outbreaks are rare FOODBORNE VIRUSES – Future Challenges Need for enhanced virus detection to document foodborne outbreaks Easy, Sensitive, Reliable Testing should eventually provide Regulatory option for shellfish and foods contaminated by human handling Control strategies for viral contamination in foods (HACCP from farm to fork) ...
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