title: Recovery of waterborne oocysts of Cyclospora cayetanensis by Asian freshwater clams (Corbicula fluminea).
abstract: Asian freshwater clams (Corbicula fluminea) were exposed for 24 hr in 38 liters of water contaminated with 1.0 x 10(5) Cyclospora cayetanensis oocysts (2.6 x 10(3) oocysts/L). The hemolyph and gill smears of 30 clams were examined by acid-fast stain on days 1, 3, 5, 7, 10, 13, and 18 postexposure (PE). Since no oocysts were detected in the water 24 hr after contamination by the membrane filter-dissolution method, the oocyst retention rate was 4.6 X 10(2) oocysts/clam. The prevalence of oocyst-positive clams significantly decreased (P < 0.01) from 93% to 47% during 13 days PE. None of the clams contained oocysts on day 18 PE; no oocysts were detected in the clam feces. The numbers of oocysts recovered from six clam size classes varied and significantly decreased with smaller clam size (P < 0.01). The lowest prevalence values of oocyst-positive clams, 45% and 34%, were observed in the two lowest size classes: 12.1-14.0 mm and 14.1-16.0 mm, respectively. The prevalence values in the remaining four classes ranged from 84% to 100%. The sampling program demonstrated that the population of 180 clams examined during the study up to 13 day PE could be assessed for C. cayetanensis positivity by random testing of a minimum of 75 clams (42%). When the two lowest clam size classes are eliminated, the population of 114 clams could be assessed by sampling a minimum of 32 clams (28%). The results demonstrate that Corbicula fluminea can recover waterborne oocysts of C. cayetanensis, and could be used as biological indicators of contamination of water with C. cayetanensis oocysts.
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Graczyk
authors.forename: Y R
authors.initials: YR
authors.lastname: Ortega
authors.forename: D B
authors.initials: DB
authors.lastname: Conn
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000469:parasitology*; D016783:Eucoccidiida / Q000302:isolation & purification*; D005618:Fresh Water / Q000469:parasitology*