United States East And Gulf Coast Shellfish Study     Earl J. Lewis1, Ronald Fayer2, James M. Trout2, Lihua Xiao3, Dorothy Howard1, Rob Palmer2, Kristie Ludwig2, and Sue Tyler1   1NOAA, NOS, Coastal Center for Environmental Health and Biomolecular Research, Oxford, MD 21654; 2USDA, Agriculture Research Station, ANRI, Animal Waste Pathogen Laboratory, Beltsville, MD 20705; 3Centers for Disease Control and Prevention, Chamblee, GA 30341     In 1997, scientists from USDA, NOAA, Johns Hopkins University School of Public Health (JHU), and CDC began a project to determine if: 1)  shellfish might be used to detect Cryptosporidium spp. and Giardia duodenalis in estuarine environments, and 2) whether there was evidence of environmental degradation in Maryland Chesapeake Bay from these fecal-borne pathogens.  Results showed Cryptosporidium oocysts survived salinities up to 30 ppt for 8-12 weeks depending on water temperature and a high prevalence of C. parvum was found within tissues, on gill surfaces, and in hemocytes of oysters at 13 sites (9 of which were open to shellfish harvest).  Oocysts recovered from oysters on several occasions were infectious in laboratory mice.  Oocysts of C. parvum were also found in hard clams and bent mussels; G. duodenalis was found in Macoma, and freshwater Corbicula clams.  Despite these findings, there have been no reports of cryptosporidiosis from eating raw shellfish.  These findings however were viewed as a potential environmental and public health issue that required further investigation.  Recently, USDA, NOAA, and CDC began to investigate Cryptosporidium spp. and G. duodenalis in oysters and hard clams from retail markets along the East and Gulf coasts of the U.S.  Traditional and molecular tools are being used to differentiate species and to determine their prevalence in shellfish.  This study will help to better understand the distribution of the organisms on a multi-state basis.  Taking advantage of such an extensive study, shellfish were also processed and fixed for histological examination.