The 1990 National Shellfish Register 



classified into four categories de- 

 scribed in Table 1 . Table 2 shows 

 estuarine acres classified since 1966. 



Public health concerns also focus on 

 changing environmental conditions 

 that affect pathogens, density and 

 distribution of human pathogens, 

 harvest practices, and the increasing 

 risks of human disease (FDA, 1990). 



Enteric Diseases. For nearly a 

 century, shellfish have been recog- 

 nized as vehicles of foodborne enteric 

 disease. Although the implementation 

 of the NSSP in 1 925 led to the control 

 of bacterial pathogens such as 

 cholera and typhoid fever, the occur- 

 rence of shellfish-associated viral 

 diseases (10,384 cases through 1989) 

 has increased (G. Richards, Pers. 

 Comm.). For example, since 1961 

 almost 1 ,400 cases of oyster- and 

 clam-associated hepatitis A have 

 been documented nationally. 



Vibrio Bacteria. Vibrios are a group of 

 bacteria found naturally in saline 

 coastal waters. Recent outbreaks 

 (334 cases between 1973 and 1987) 

 have been associated with Vibrio 

 cholerae, V. vulnificus, and 

 V. parahaemolyticus. Ingestion of 

 Vibrio can cause gastroenteritis and 

 even death, particularly in compro- 

 mised patients. In 1988, 43 cases of 

 V. vulnificus were reported, resulting 

 in 18 deaths nationwide (Centers for 

 Disease Control, 1989). However, 

 only 27 cases and twelve deaths were 

 linked to shellfish consumption (S. 

 Rippey, Pers. Comm.). In 

 Apalachicola Bay (FL), V. cholerae 

 have been found in approved and 



prohibited waters; there was no 

 correlation between coliform bacteria 

 levels and Vibrio (Blake and Roderick, 

 1983). Deaths linked to out-of-state 

 shipments suggest that handling and 

 transport time may affect the pathoge- 

 nicity of the organisms. 



Marine Biotoxins. Shellfish-growing 

 waters may be affected by blooms of 

 certain species of dinoflagellates or 

 diatoms. Blooms which produce 

 marine biotoxins can cause a variety 

 of human illnesses. On the North 

 Atlantic Coast, paralytic shellfish 

 poisoning (PSP) is caused by 

 Alexandrium tamarense, which 



Table 2. Classified Estuarine Acres 

 (x 1,000), 1966-1990 



