Seafood Safety (1991) / Chapter Skim
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3. Microbiological and Parasitic Exposure and Health Effects
3. Microbiological and Parasitic Exposure and Health Effects
Pages 30-86
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From page 30... ...
In particular, immunocompromised individuals, those with defective liver function, people afflicted with diabetes, and the elderly should be warned never to eat raw shellfish. The greatest risks from the consumption of raw molluscan shellfish could be minimized by research to develop valid indicators of human enteric viruses for proper classification of shellfish growing waters; by implementing and maintaining proper treatment 30
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From page 31... ...
This cannot be achieved by the visual or organoleptic inspection currently used for meat and poultry. Seafood inspection requires the development of valid microbiological guidelines to accurately assess human health risk from raw and processed seafoods.
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From page 32... ...
No Yes 2 Enteral non-A, non-B hepatitis No Yes 2 Hepatitis A Yes Yes 2, 3 Organisms That Cause Disease Most Often in Special Population Groups Mbno vulnipcus~ Yes Yes Rotaviruse Yes No Listena Yes No Organisms with Uncertain Roles as Food~borne Pathogens Aeromonas hydrophilaf Yes Yes Plesiomonas shigelloides Yes Yes Edwardsiella tarda Yes No 1, 3 a (1) Harvest water/associated with naturally occurring aquatic bacteria; (2)
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From page 33... ...
b Clostridium botulinum Shigellab Staphylococcus aureus 1 3 Bacillus cereus 3 26 3 1 4 2 9 6 Total outbreaks/cases 38 351 40 476 2,198 Unknown agentsC 16 203 88 3,271 5,098 a CDC reports disease from all crustacean and molluscan shellfish; NETSU reports only bivalve molluscan shellfish incidence. b Pathogens that may be associated with pollution or processing/handling - most molluscan shellfishassociated cases due to pollution.
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From page 34... ...
z Go Do o c— o v' In 'e en a en ED o · c)
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From page 35... ...
Staphylococcus aureus 3 9. Trio cholerae Of 2 Total outbreaks/cases 51 515 a Unknown etiologies are probably not all microbiological pathogens.
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From page 36... ...
Most of these bacteria fall within the family Vibrionaceae, which includes the genera rbno' Aeromonas, and Plesiomonas. These bacteria are generally not associated with fecal contamination of harvest waters, and some studies suggest an inverse relationship between counts of certain species and fecal coliform levels (Kaper et al., 1979; Tamplin et al., 1982~.
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From page 37... ...
The number of cases of cholera associated with these strains is relatively small (in the range of 50 cases since 1973~; their significance lies in their potential for causing severe disease in otherwise healthy hosts. Epidemiology and risk assessment Epidemiologic investigations have associated ~ cholerae O1 illness with eating crabs, shrimp, and raw oysters harvested along the Gulf Coast (Blake et al., 1980~.
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From page 38... ...
oyster lots harvested during warm summer months
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From page 39... ...
In support of the latter hypothesis, non-O1 ~ cholerae strains were isolated from 13 (2.7%) of 479 persons in a cohort of physicians attending a convention in New Orleans in late September; among persons eating raw oysters, 4% had non-O1 ~ cholerae in their stool.
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From page 40... ...
Although sporadic cases associated with the consumption of raw oysters have occurred, there does not appear to be the same strong association with consumption of raw oysters as reported
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From page 41... ...
With nonradioactively labeled oligonucleotide probes it may be possible to identify potentially pathogenic strains within a matter of hours. However, no effort has been made to make such probes commercially available or to assess their utility as public health tools.
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From page 42... ...
Although data are limited, some studies reported that close to 100% of oyster lots harvested in some areas during warm summer months have been positive for ~ vulnipcus, and in one study, 11% of the blue crabs harvested from Galveston Bay during summer months had the organism in their hemolymph (Davis and Sizemore, 1982; Tamplin, 1990~. Occurrence of ~ vulnipcus-induced primary septicemia is significantly associated with eating raw oysters (Tacket et al., 1984~.
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From page 43... ...
expected, given the frequency with which the organism has been identified in shellfish and the amount of shellfish consumed in these areas. This may reflect differences in virulence among strains, the effect of infectious dose (i.e., the minimum number of organisms needed to cause disease)
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From page 44... ...
Low-dose gamma irradiation of live shellstock and fresh or frozen seafood products has been shown to be extremely effective in the elimination of Vbno species (Giddings, 1984; Kilgen et al., 1988~. Rapid diagnostic techniques are available for ~ vulnipcus, based both on agglutination reactions with specific antisera (Simonson and Siebeling, 1986)
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From page 45... ...
The risk of infection with these organisms can likely be reduced by strategies similar to those used for other rbno species: that is, by using good manufacturing practices (GMPs) involving immediate and proper refrigeration, by possibly limiting shellfish harvesting to cooler months, by monitoring rbno counts in summer months for management purposes, by using low-dose irradiation for processing raw seafoods or live shellstock, and by advising persons in high-risk groups to avoid consumption of raw shellfish.
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From page 46... ...
It is possible that few strains carry virulent characteristics that enable them to cause human disease, but there is currently no way of differentiating potentially pathogenic strains from nonpathogenic ones. According to the NETSU data base, P
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From page 47... ...
Clonorchis sinensis, or the Chinese liver fluke, is transmitted by eating raw or undercooked freshwater fish containing cyst stages of the organism. The organism is endemic in east Asia in a zone extending from Japan to Vietnam.
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From page 48... ...
D Iatum is acquired by eating raw freshwater fish containing appropriate plerocercoids (Healy and Juranek, 1979~.
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From page 49... ...
Viral Human Enteric Pathogens More than 100 enteric viruses can be found in human feces. Families of viral pathogens associated with pollution of harvesting waters include picornaviruses, reoviruses, adenoviruses, caliciviruses, astroviruses, and unclassified viruses such as Norwalk and Norwalk-like viruses, Snow Mountain agent, small round viruses, and non-A, non-B hepatitis virus (NANB)
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From page 50... ...
Other marine animals, including lobsters, sandworms, detr~tai feeding test, and conch, have been shown to take up enteric viruses when marine waters were experimentally seeded with these viruses, but viral uptake from naturally polluted water has not been reported in field studies. The only seafood implicated to date in the transmission of enteric virus from contaminated estuarine waters has been molluscan shellfish (Gerba, 1988~.
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From page 51... ...
There is currently no valid indicator of human enteric viruses such as HAV in shellfish growing waters. Caliciviruse s and As t rovi ru se s Caliciviruses, like all enteric viruses, are found in human feces and are responsible for many cases of gastroenteritis.
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From page 52... ...
are usually difficult to obtain. Disease Control for Human Enteric Viruses Proper classification of shellfish growing waters based on valid human enteric virus indicators, as well as implementation and maintenance of proper treatment and disposal of sewage to prevent human enteric virus contamination of shellfish harvesting waters, are the most effective measures to deter raw shellfish-associated infections by these viruses.
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From page 53... ...
Bacterial Pathogens Salmonella Outbreaks of seafood-borne salmonellosis were reported to CDC between 1978 and 1987 (Tables 3-2-3-4 and 3-9~; however, no cases of salmonellosis associated with shellfish consumption were reported to NETSU in the same period (Tables 3-2 and 3-3~. Typhoid fever, due to infection by S
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From page 54... ...
montevideo, the outbreak serotype. Consumption of raw shellfish harvested from sewage-polluted waters also has resulted in Salmonella infections (Flowers, 1988a)
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From page 55... ...
The last shellfish-associated typhoid outbreak reported in the NETSU data base occurred in 1954 (Rippey and Verber, 1988~. The risk of typhoid fever associated with imported seafood may vary, depending on the rates of infection in the country of origin and the degree of Dollution ~ in, ~ D ~ r ot harvest waters.
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From page 56... ...
Thus, although the risk of Campylobacter infection associated with eating raw shellfish appears low, the data are inadequate to make any assessment of attributable risk. Control of C
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From page 57... ...
In recent years, L'stena has been implicated in outbreaks involving contaminated cabbage in Nova Scotia, fresh cheese in California, and pasteurized milk in Boston (FIeming et al., 1985; Linnan et al., 1988; Schlech et al., 1988~. An outbreak of perinatal listeriosis was tentatively attributed to consumption of raw finfish and shellfish in New Zealand, although it is not clear whether patients consumed raw seafood more often than persons who did not become ill (Lennon et al., 1984~.
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From page 58... ...
monocytogenes not be present in readyto-eat seafood products such as crabmeat or smoked fish. The restriction does not apply to raw products that will be cooked before eating.
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From page 59... ...
All cases occurred in the home or as a result of eating homemade seafood products. No domestic case of botulism from commercially prepared seafoods has been reported in the United States in recent years, although canned salmon from Alaska has caused two incidents in Europe.
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From page 60... ...
? 5 Total 38 a Alaskan fermented fish eggs produced by burial in the ground.
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From page 61... ...
One of these outbreaks, which involved nine cases, was shellfish associated (Table 3-3~. The other outbreak, involving three cases, was associated with other seafood products (Table 3-4~.
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From page 62... ...
There are no documented cases of transmission of human enteric viruses other than hepatitis A from seafood products contaminated at the processing, distribution, or food handling level (Bryan, 1986; CDC, 1981a-c, 1983a,b, 1984, 1985, 1989; Rippey and Verber, 19884. Viruses do not replicate in seafood products, so temperature abuse is not a factor.
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From page 63... ...
For equal safety, imported fully processed canned seafood products must be made by processes that meet domestic FDA requirements, including process approval, adequate recordkeeping, and employment of certified retort/operator supervisors. Semiconserved canned fishery products may contain living microorganisms because they receive milder heat treatment in pasteurization (Delmore and Crisley, 1979; Eklund, 1982; Lerke and Farber, 1971~.
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From page 64... ...
It is well established that modified atmosphere (MA) storage of seafood products will extend the shelf life considerably by inhibiting the normal psychrotrophic microflora and reducing the spoilage rate.
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From page 65... ...
Of the enteric viruses, only hepatitis A virus, Norwalk virus, Snow Mountain agent, caliciviruses, astroviruses, NANB enteral hepatitis, and unspecified hepatitis have
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From page 66... ...
Human enteric viruses from naturally occurring contamination have been isolated in field studies only from molluscan shellfish and from blue crabs collected at a sludge dump in the North Atlantic. Other marine animals, including lobsters, sandworms, detrital feeding fish, and conch, have been shown to take up enteric viruses seeded into marine waters experimentally, but this has not been reported from field studies to occur naturally.
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From page 67... ...
Efforts can also be directed toward reducing or eliminating organisms present in shellfish after harvest. The self-cleansing of some enteric viruses and marine vibrios may not proceed at the same rate as for enteric bacteria and indicators, which suggests that current techniques for deputation may be of little benefit in limiting contamination with Vibrionaceae.
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From page 68... ...
Pathogens Associated with Pollution Control of pollution-associated agents generally translates into identifying sewage contamination of haIvest areas. The only seafood products that are regulated by microbiological indicator standards for growing water quality are molluscan shellfish.
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From page 69... ...
Fecal coliforms are present in high numbers in untreated sewage and are considered "indicators" of the possible bacterial and viral human enteric pathogens that may also be found in feces. The allowable numbers of fecal coliforms in shellfish growing waters were based on the relationship between total coliform counts and the number of Salmonella Phi present during a typhoid fever epidemic in the 1920s (FDA, 1989a)
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From page 70... ...
, the United States has only three types of general regulatory microbiological indicator criteria for other seafoods: 1. Microbiological standards FDA's GMP requirement that thermally processed low-acid foods packaged in hermetically sealed containers be commercially sterile · FDA's microbiological standards for "approved," "conditionally approved," "restricted," or "prohibited" molluscan shellfish growing waters, used in conjunction with a sanitary survey as described above 2.
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From page 71... ...
Similar studies by the FDA agreed that Gulf of Mexico Coast oysters harvested from approved growing waters in summer months may contain excessively high levels of non-E. cold fecal coliforms and not represent an excessive health hazard (FDA, 1989a)
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From page 72... ...
Rather, sewageassociated human illnesses appear most frequently to have a viral etiology, and viruses tend to be species specific. Therefore, an indicator of human enteric viruses in water and in seafoods is needed.
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From page 73... ...
This will require intelligent assessment of the microbiological hazards likely to be particularly troublesome in different exporting countries and the risks associated with in-country handling and processing practices. Because of the high risks associated with raw molluscan shellfish, the importation of shellfish for raw consumption should be prohibited unless standards for the microbial quality of harvest waters and postharvest processing in the exporting country are fully equivalent to those in the United States.
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From page 74... ...
From a microbiological standpoint, the most important ethnic practices involve consumption of raw and fermented seafood products. Eating raw fish is most common among Americans of Asiatic origin and presents potential problems associated with parasites and ~bno infection.
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From page 75... ...
Many of the microorganisms of concern in growing waters and abusive conditions in processing, handling, or preparation of other seafood products are also of concern in aquaculture. Two different areas of concern for aquaculture are pathogens known to cause disease in both fish and humans (e.g., Edwardsiella lards and Aeromo~zas hydrophila)
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From page 76... ...
The vast majority of these illnesses are associated with the consumption of raw molluscan shellfish taken from harvest waters contaminated with raw or poorly treated human sewage. Although these are the most common seafoodassociated illnesses, they tend to be relatively mild with no associated mortality.
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From page 77... ...
~ Valid indicators for contamination of growing waters by human pathogens must be developed. Seafood-borne infections by human enteric viruses in raw and improperly cooked molluscan shellfish could be decreased significantly by the development of valid growing water indicatorts)
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From page 78... ...
· Continuous, enhanced efforts should be undertaken to educate all health professionals, food handlers, and consumers regarding the microbiological risks of seafood-borne illness and the appropriate means of minimizing such risks, including immediate and adequate refrigeration, proper cooking, avoiding recontamination of cooked products by raw products, proper sanitation, and good personal hygiene, especially at the food service level. · A food-borne illness surveillance system sufficient for risk identification and regulatory program planning and evaluation must be developed.
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From page 79... ...
1983. Bacteriological quality of fresh seafood products from Seattle retail markets.
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From page 80... ...
1984. Food-borne disease outbreaks, Annual summary 1983: Reported morbidity and mortality in the United States.
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From page 81... ...
Sanitation of shellfish growing areas. National Shellfish Sanitation Program Manual of Operations Part I
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From page 82... ...
1988. Microbiological standards, guidelines, and specifications and inspection of seafood products.
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From page 83... ...
1989. Final Report on the Current National Status of the Relationships of Indicators, Human Enteric Pathogens and Potential Health Risks Within a Total Environmental Assessment.
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From page 84... ...
Role of Norwalk virus.
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From page 85... ...
1987. Seasonal variation in the fecal coliform population of Louisiana oysters and its relationship to microbiological quality.
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From page 86... ...
1988. Typhoid fever and acute non-A non-B hepatitis after shellfish consumption.
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