This chapter emphasizes domestic production of wild caught fish and shellfish. The same pathogens are of concern in imported seafood, although the risks of specific pathogens vary depending on conditions in the growing waters at the point of harvest, as well as subsequent handling and processing. Aquaculture presents a different set of potential concerns, which are summarized in a separate section below (also see Chapters 5 and 8).

PATHOGENS NATURALLY PRESENT IN MARINE OR FRESHWATER ENVIRONMENTS

Naturally Occurring Marine Bacteria Associated with Human Disease

A number of free-living estuarine and freshwater bacteria may be associated with human disease. Most of these bacteria fall within the family Vibrionaceae, which includes the genera Vibrio, 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). Counts tend to be highest in warm summer months, particularly when water temperature exceeds 15-20°C (Baross and Liston, 1970).

TABLE 3-5 Vibrionaceae Identified with Shellfish-Associated Human Disease

Pathogen

Clinical Features

Implicated Shellfish Vehicle

 

Diarrhea

Septicemia

Most Common

Other

Vibrio cholerae O1

++a

 

Crab

Oyster

Vibrio cholerae non-O1

++

+b

Oyster

 

Vibrio parahaemolyticus

++

(+)c

Shellfish

 

 

 

 

(shrimp, crab)

 

Vibrio fluvialis

++

 

?e

 

Vibrio mimicus

++

 

Oyster

 

Vibrio hollisae

++

(+)

Shellfish

 

 

 

 

(unspecified)

 

Vibrio furnissii

++

 

?

 

Vibrio vulnificus

+

++

Oyster

Crab

Aeromonas hydrophila

?d

 

?

 

(including Aeromonas caviae and Aeromonas sobria)

 

 

 

 

Plesiomonas shigelloides

++

 

Oyster

 

a Most common clinical manifestation.

b Occasional clinical manifestation.

c Rare clinical manifestation.

d Suspected, but not proven clinical manifestation.

e Unsure if shellfish can be implicated as a vehicle.



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