Susceptibility of the Chesapeake Bay to Environmental Contamination with Cryptosporidium parvum

Cryptosporidium parvum causes cryptosporidiosis in people with disorders of the immune system. The oocysts are quite persistent and can be spread by up to 80 other species of animal, or via food or water, causing diarrhea that can be life threatening. Thirty oysters were collected from each of six Chesapeake Bay locations and analyzed for the presence of Cryptosporidium oocysts. Either hemocytes of gill washings from all specimens from all locations contained oocysts. During the autumn of 1997, fresh Canada Geese droppings were collected at nine sites near the Chesapeake bay. At seven of the sites, fecal matter contained oocysts. Although finding oocysts in oysters, which are often consumed without cooking seems an ominous public health finding, the oocysts could be those of one of the seven species of Cryptosporidium that are noninfectious to humans. Oysters may be useful biological indicators of water contamination with Crytosporidium, however.