title: Correlation between diarrhea severity and oocyst count via quantitative PCR or fluorescence microscopy in experimental cryptosporidiosis in calves.
abstract: Cryptosporidium is an important diarrhea-associated pathogen, however the correlation between parasite burden and diarrhea severity remains unclear. We studied this relationship in 10 experimentally infected calves using immunofluorescence microscopy and real-time polymerase chain reaction (qPCR) (N = 124 fecal samples). The qPCR data were corrected for extraction/amplification efficiency and gene copy number to generate parasite counts. The qPCR and microscopic oocyst quantities exhibited significant correlation (R(2) = 0.33, P < 0.05), however qPCR had increased sensitivity. Upon comparison with diarrhea severity scores (from 0 to 3), a PCR-based count of ≥ 2.6 × 10(5) parasites or an immunofluorescence microscopy count of ≥ 4.5 × 10(4) oocysts were discriminatory predictors of moderate-to-severe diarrhea (versus no-to-mild diarrhea), with accuracies and predictive values of 72-82%. In summary, a quantitative approach for Cryptosporidium can refine predictive power for diarrhea and appears useful for distinguishing clinical cryptosporidiosis versus subclinical infection.
authors.affiliation: Division of Infectious Diseases and International Health, Department of Medicine, University of Virginia, Charlottesville, Virginia; Department of Population Medicine and Diagnostic Science, College of Veterinary Medicine, Cornell University, Ithaca, New York do2s@eservices.virginia.edu.
authors.forename: Darwin J
authors.initials: DJ
authors.lastname: Operario
authors.affiliation: Division of Infectious Diseases and International Health, Department of Medicine, University of Virginia, Charlottesville, Virginia; Department of Population Medicine and Diagnostic Science, College of Veterinary Medicine, Cornell University, Ithaca, New York.
authors.forename: Lauren S
authors.initials: LS
authors.lastname: Bristol
authors.affiliation: Division of Infectious Diseases and International Health, Department of Medicine, University of Virginia, Charlottesville, Virginia; Department of Population Medicine and Diagnostic Science, College of Veterinary Medicine, Cornell University, Ithaca, New York.
authors.forename: Janice
authors.initials: J
authors.lastname: Liotta
authors.affiliation: Division of Infectious Diseases and International Health, Department of Medicine, University of Virginia, Charlottesville, Virginia; Department of Population Medicine and Diagnostic Science, College of Veterinary Medicine, Cornell University, Ithaca, New York.
authors.forename: Daryl V
authors.initials: DV
authors.lastname: Nydam
authors.affiliation: Division of Infectious Diseases and International Health, Department of Medicine, University of Virginia, Charlottesville, Virginia; Department of Population Medicine and Diagnostic Science, College of Veterinary Medicine, Cornell University, Ithaca, New York.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Houpt
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000469:parasitology* / Q000503:physiopathology; D003457:Cryptosporidiosis / Q000469:parasitology* / Q000503:physiopathology; D003967:Diarrhea / Q000469:parasitology / Q000503:physiopathology / Q000662:veterinary*; D008856:Microscopy, Fluorescence / Q000379:methods*; D033661:Oocysts; D010270:Parasite Egg Count; D016133:Polymerase Chain Reaction / Q000379:methods*