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 journalArticle

333 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
Publication statusPublished - 1999


ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Immunology

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