Commercial Atlantic blue crabs (Callinectes sapidus) were exposed to 2.0 ؋ 10 4 infectious waterborne oocysts of Cryptosporidium parvum. The study demonstrated that blue crabs can transfer C. parvum oocysts to persons involved in handling or preparing crabs and that they may contaminate other surfaces or products during storage.Cryptosporidium parvum is a human enteric pathogen that can be transmitted very efficiently via the fecal-oral route (i.e., autoinfection and person-to-person) and indirectly via contact with contaminated water, including consumption and recreational activities (5). Edible crabs may take up and retain human-virulent bacterial contaminants (1, 10, 11, 13) and organic and inorganic pollutants from ambient water and sediments at levels posing risks to consumers (12). There is no published information on contamination of crabs with Cryptosporidium, a waterborne pathogen commonly reported from coastal waters (3, 6). However, our previous study demonstrated mechanical passage of C. parvum oocysts via handling of fish caught in urban watersheds to the hands of recreational anglers (16). The purposes of the present study were to determine if commercially harvested Atlantic blue crabs (Callinectes sapidus), which are widely consumed, can serve as a vehicle for infectious waterborne oocysts of C. parvum and if the handling of crabs collected from Cryptosporidium-contaminated water can result in oocyst transfer to the handler's hands.A 120-liter-capacity marine tank was filled with 4 liters of artificial seawater of 12-ppt salinity (9) to which 2.0 ϫ 10 4 C. parvum oocysts were added. The oocysts were tested and found to be infectious to neonatal BALB/c mice (6). C. parvum oocysts were eluted from 12 blue crabs (C. sapidus) purchased from a local market by sprinkling 0.5 liter of the eluting fluid (4) on the crabs' surfaces and then collecting all the fluid into a single plastic bottle. The crabs were alive and actively ventilating with their mouthpart appendages during the experiments. The crabs were left in the tank for 24 h, and then the oocysts were eluted from the individual surfaces of six randomly selected crabs as described above and the fluid was collected into six corresponding plastic bottles. The oocysts were eluted collectively from the surfaces of the remaining crabs, and the fluid was collected into a single plastic bottle. The crabs were handled by a single person, and the hands of that person were washed in a plastic ziplock bag (16) containing 0.5 liter of eluting fluid (4). The tank water was collected into a plastic container, and the tank was washed with 1 liter of the eluting fluid (4), which was added to the container. The samples were processed by a cellulose acetate membrane filter dissolution method (4), and the recovered material was tested by combined fluorescence in situ hybridization and a direct immunofluorescent antibody assay for C. parvum (7-9).

Baltimoreans with HIV/AIDS are engaging in recreational water activities in urban waters that may expose them to waterborne pathogens and recreational water illnesses. Susceptible persons, such as patients with HIV/AIDS, should be cautioned regarding potential microbial risks from recreational water contact with surface waters.

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