MULTILOCUS GENOTYPIC ANALYSIS OF CRYPTOSPORIDIUM-PARVUM ISOLATES FROMDIFFERENT HOSTS AND GEOGRAPHICAL ORIGINS

The genetic analysis of oocysts recovered from the stools of humans an d animals infected with Cryptosporidium parvum has consistently shown the existence of two distinct genotypes, One of the genotypes is found exclusively in some human infections, whereas the other genotype is f ound in human as well as in animal infections. On the basis of these o bservations and the results of published epidemiological studies with single polymorphic markers, the existence of two separate transmission cycles has been postulated, one exclusively anthroponotic and the oth er involving both animals and humans. To test this hypothesis, C. parv um isolates of different geographic and host origins were analyzed by using unlinked genetic polymorphisms. A total of 28 isolates originati ng from Europe, North and South America, and Australia were examined. Isolates clustered into two groups, one comprising both human and anim al isolates and the other comprising isolates only of human origin. Th e absence of recombinant genotypes is consistent with two reproductive ly isolated populations within the species C. parvum.