Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 3/12/2003
Publication Date: 7/30/2003
Citation: Lewis, E.J., Fayer, R., Trout, J.M., Xiao, L. 2003. U.S. East and Gulf Coast Shellfish Study - The Rest of the Story. [Abstract]. Annual Eastern Fish Health Workshop, April 21, 2003, Gettysburg, PA. p.1.
Technical Abstract: Results of a 1997 study conducted by NOAA, USDA, Johns Hopkins University School of Public Health (JHU), and CDC showed a high prevalence of Cryptosporidium parvum within tissues, on gill surfaces, and in hemocytes of oysters, Crassostrea virginica, at 13 sites in Chesapeake Bay, MD; 9 of which were open to shellfish harvest. In several instances oocysts recovered from oysters were infectious in laboratory mice. Oocysts of C. parvum were also found in hard clams and bent mussels. The presence of these organisms indicates pollution from human or animal feces in shellfish growing waters. These findings were viewed as a potential environmental and public health issue that required further investigation. To better understand the distribution of Cryptosporidium on a multi-state basis, a 2001 and 2002 study by NOAA, USDA, and CDC scientists investigated Cryptosporidium spp. in oysters and hard clams obtained from retail markets along the East and Gulf coasts of the U.S. A total of 49 collection sites were examined, 33 oyster and 16 clam. Cryptosporidium oocysts were detected in at least 1 sample of shellfish from New Brunswick, Canada and 14 of 17 states. In all, 4% of 1225 oysters and clams examined by immunofluorescent antibody (IFA) methodology were found to harbor Cryptosporidium. Cryptosporidium DNA was also detected by Polymerase Chain Reaction (PCR) in 27% of 245 pools of shellfish examined. Collectively, these findings show multiple species of Cryptosporidium, some that are potentially infectious for humans, were found in commercial shellfish from 59% (29/49) of sites examined along the Atlantic and Gulf coasts by either microscopy or molecular assays. These results, acquired during a time of drought, may or may not be indicative of the long-term prevalence of Cryptosporidium in coastal shellfish. In addition, there have been no reports of cryptosporidiosis linked to eating raw shellfish.