DNA-SEQUENCE SIMILARITY BETWEEN CALIFORNIA ISOLATES OF CRYPTOSPORIDIUM-PARVUM

We evaluated whether nucleic acid amplification with primers specific for Cryptosporidium parvum followed by automated DNA sequence analysis of the PCR amplicons could differentiate between California isolates of C. parvum obtained from livestock, humans, and feral pigs. Almost c omplete sequence identity existed among the livestock isolates and bet ween the livestock and human isolates. DNA sequences from feral pig is olates differed from those from livestock and humans by 1.0 to 1.2%. T he reference sequence obtained by Laxer et al. (M.A. Laxer, B.K. Timbl in, and R.J. Patel, Am.J.Trop.Med.Hyg. 45:688-694, 1991.) differed fro m California isolates of C. parvum by 1.8 to 3.2%. These data suggest that DNA sequence analysis of the amplicon of Laxer et al. does not al low for differentiation between various strains of C. parvum or that o ur collection of isolates obtained from various hosts from across Cali fornia was limited to one strain of C. parvum.