IDENTIFICATION OF GENETIC-HETEROGENEITY IN THE CRYPTOSPORIDIUM-PARVUMRIBOSOMAL REPEAT

Oocysts of the protozoan parasite Cryptosporidium parvum are found in most surface waters and can contaminate municipal water supplies, as d emonstrated by recent outbreaks of cryptosporidiosis. A method capable of fingerprinting C. parvum isolates from the environment would facil itate the study of epidemiology and transmission cycles and aid in the implementation of preventive measures to reduce water contamination b y oocysts. In this study, we report polymorphism in C. parvum isolates on the basis of analysis of random amplified polymorphic DNA and nucl eotide sequences in a region of the 18S rRNA and the internal transcri bed spacer 1. Isolate-specific primers for these two regions were desi gned, and PCR tests capable of discriminating between isolates were de veloped. In both PCR assays, the five C. parvum isolates analyzed segr egated into two subgroups. One group consisted of isolates that origin ated directly from human patients, and the other group had various hos t origins and had been propagated in laboratory animals. These results demonstrate the feasibility of distinguishing C. parvum isolates by s equence-specific PCR tests.