title: Cryptosporidium parvum: treatment effects and the rate of decline in oocyst infectivity.
abstract: Cryptosporidium parvum has become the focus of numerous studies on waterborne disease and transmission in response to outbreaks endangering populations worldwide. The Foci Detection Method-Most Probable Number Assay (FDM-MPN) is an in vitro cell culture method that has been developed and used to determine the quantity of infectious C. parvum oocysts. This research evaluated 2 vendor's producing oocysts, Sterling Parasitology Laboratory (SPL) and Pleasant Hill Farms (PHF) (now known as Bunch Grass Farms as of 12/03), classified as young (<30 days) and aged (>165 days), for comparison of treatments (bleach, antibiotic, no treatment) before cell culture, as well as an age study, to determine any lot-to-lot differences and vendor differences regarding the rate of decline in infectivity. Bleach treatment (0.525%) appeared to be the optimum method for the FDM-MPN with regards to maximum infectivity, efficient disinfection, with no visible antagonistic affects on the C. parvum oocysts. The age study revealed that lot-to-lot variability within each vendor stayed within 1 log10 difference, while the rates of decline in infectivity measured until 107 and 120 days of age when stored at 4 C for SPL and PHF were -0.016 and -0.014 log10 infectious oocysts/day, respectively. These results provide insight regarding C. parvum oocyst viability in a fecal population, as well as useful knowledge for further methods development.
authors.affiliation: Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599, USA. angiecou@e-mail.unc.edu
authors.forename: Angela D
authors.initials: AD
authors.lastname: Coulliette
authors.forename: Debra E
authors.initials: DE
authors.lastname: Huffman
authors.forename: Theresa R
authors.initials: TR
authors.lastname: Slifko
authors.forename: Joan B
authors.initials: JB
authors.lastname: Rose
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003457:Cryptosporidiosis / Q000469:parasitology; D016785:Cryptosporidium parvum / Q000187:drug effects* / Q000472:pathogenicity; D006801:Humans; D033661:Oocysts / Q000187:drug effects / Q000472:pathogenicity; D010400:Penicillin G / Q000494:pharmacology; D012973:Sodium Hypochlorite / Q000494:pharmacology*; D013307:Streptomycin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D000666:Amphotericin B; D012973:Sodium Hypochlorite; D010400:Penicillin G; D013307:Streptomycin