Submitted to: Emerging Infectious Diseases
Publication Type: Abstract Only
Publication Acceptance Date: 3/11/1998
Publication Date: N/A
Technical Abstract: Oysters, Crassostrea virginica, from the Maryland portion of the Chesapeake Bay were previously reported to harbor C. parvum oocysts infectious for mice. In the present study, oysters were collected for the state's shellfish health program from 5 commercial oyster bars in tributaries of the Chesapeake Bay in Oct. and Nov. 1997. Sites A-E were located in the Wicomico, Nanticoke, Potomac and Patuxent Rivers and in Fishing Bay, respectively. Hemolymph was obtained and gills were removed within 3 days of collection. On each 2 glass microscope slides 200 ul of hemolymph or gill wash sediment from each oyster was dried and then stained with Merifluor immunofluorescence reagents to detect oocysts of Cryptosporidium. Of 30 oysters from sites A-E, 28, 29, 26, 29 and 29, respectively, harbored oocysts. Tubes of hemolymph or gill washings, pooled from groups of 6 oysters at each site, were refrigerated until slides were examined. Pools from oysters with the most oocysts were selected for genotyping and/or bioassay in mice PCR for TRAP C2 and beta-tubulin genes confirmed the presence of Cryptosporidium oocysts from oysters at sites B and E, TRAP-C2 revealing genotype 2. All mouse bioassays were negative. The finding of oocysts in oysters from commercial oyster bars raises concern for potential foodborne infection for persons eating raw or undercooked oysters and will be discussed with respect to typing and bioassay findings.