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Volume 5, Number 5—October 1999


Cryptosporidium parvum in Oysters from Commercial Harvesting Sites in the Chesapeake Bay

Ronald Fayer*Comments to Author , Earl J. Lewis†, James M. Trout*, Thaddeus K. Graczyk‡, Mark C. Jenkins*, James Higgins*, Lihua Xiao§, and Altaf A. Lal§
Author affiliations: *U.S. Department of Agriculture, Beltsville, Maryland, USA; †National Oceanic and Atmospheric Administration, Oxford, Maryland, USA; ‡Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland, USA; and §Centers for Disease Control and Prevention, Atlanta, Georgia, USA

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Identification of Cryptosporidium parvum oocysts recovered from oysters in the Chesapeake Bay

Site Location Bay location 
or river system Fall 1997
Winter 1998
Fall 1998
IFA PCRa Mice infectivity IFA PCR Mice infectivity IFA Cp11 Mice infectivity Waterb
A Mt.Vernon Wharf Wicomico 28c ND Negd 15 BT Pos 4 Pos Neg ND
B Wetipquin Nanticoke 29 BT Neg 3 Neg Neg 8 Pos Neg 79
C Halfway Mark Fishing Bay 29 HT Neg 0 BT & HT Neg 1 Pos Neg ND
D Beacon Potomac 26 BT ND ND ND ND 2 Pos Pos 10
E Holland Point Patuxent 28 BT Pos ND ND ND 1 Pos Neg 31
F Back Cove Tangier Sound ND ND ND 2 BT Neg 6 ND Neg 8
G Old Woman's Leg Tangier Sound ND ND ND 0 BT Neg 0 ND Neg ND

aPolymerase chain reaction and restriction fragment-length polymorphism (PCR-RFLP) on small subunit rRNA gene, 18s.
bNumber of oocysts recovered per liter of filtered bay water.
cNumber of oysters found positive for oocysts out of 30 oysters examined from each site.
dNeg indicates that PCR using Cp11 primers failed to detect Cryptosporidium DNA in the DNA extracted from the ilea of mice that were intubated with pooled hemolymph and gill washings from oysters.
HT, human genotype; BT, bovine genotype; ND, not done; IFA, immunofluorescent assay; PCR, polymerase chain reaction.

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