Virulence of three distinct Cryptosporidium parvum isolates for healthy adults

Pablo C. Okhuysen, Cynthia L. Chappell, Joseph H. Crabb, Charles R. Sterling, Herbert L. DuPont

    Research output: Contribution to journalArticlepeer-review

    381 Scopus citations


    The infectivity of three Cryptosporidium parvum isolates (Iowa [calf], UCP [calf], and TAMU [horse]) of the C genotype was investigated in healthy adults. After exposure, volunteers recorded the number and form of stools passed and symptoms experienced. Oocyst excretion was assessed by immunofluorescence. The IC50 differed among isolates: Iowa, 87 (SE, 19; 95% confidence interval [CI], 48.67-126); UCP, 1042 (SE, 1000; 95% CI, 0-3004); and TAMU, 9 oocysts (SE, 2.34; 95% CI, 4.46-13.65); TAMU versus Iowa, P = .002 or UCP, P = .019. Isolates also differed significantly (P = .045) in attack rate between TAMU (86%) and Iowa (52%) or UCP (59%). A trend toward a longer duration of diarrhea was seen for the TAMU (94.5 h) versus UCP (81.6 h) and Iowa (64.2 h) isolates. C. parvum isolates of the C genotype differ in their infectivity for humans.

    Original languageEnglish (US)
    Pages (from-to)1275-1281
    Number of pages7
    JournalJournal of Infectious Diseases
    Issue number4
    StatePublished - 1999

    ASJC Scopus subject areas

    • General Medicine


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