Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2002
Publication Date: 12/1/2002
Citation: XIAO, L., SULAIMAN, I., RYAN, U., ZHOU, L., ATWILL, E.R., TISCHLER, M.L., ZHANG, X., FAYER, R., LAL, A.A. HOST ADAPTION AND HOST-PARASITE CO-EVOLUTION IN CRYPTOSPORIDIUM: IMPLICATIONS FOR TAXONOMY AND PUBLIC AND PUBLIC HEALTH. INTERNATIONAL JOURNAL FOR PARASITOLOGY. 2002. 32:1773-1785. Interpretive Summary: Cryptosporidium species are food and waterborne pathogens of humans, some of which are transmitted from humans and others from food animals, companion animals, and wildlife. To better determine the extent of relatedness among 15 new isolates of Cryptosporidium from a variety of animals, 3 genes from each isolate were sequenced and compared. Closely related sequences were found in parasites from closely related hosts. Data suggest that the bovine genotype of C. parvum was originally a parasite of rodents and C. meleagridis, although first isolated from turkeys and recently found in human infections, was originally a parasite of mammals. By extrapolation from these findings it may be possible to predict the public health risk of additional new isolates based on gene sequence data.
Technical Abstract: To assess the genetic diversity and evolution of Cryptosporidium parasites, the small subunit (SSU) rRNA, actin, and 70 kDa heat shock protein (HSP70) genes of 15 new Cryptosporidium parasites were sequenced. Sequence data were analyzed and compared with data previously obtained from other Cryptosporidium parasites. Results of this multi-locus genetic characterization indicate that host-adaptation is a general phenomenon in the genus Cryptosporidium, because specific genotypes were usually associated with specific groups of animals. On the other hand, host-parasite co-evolution is also common in Cryptosporidium, as closely related hosts usually had related Cryptosporidium parasites. Results of phylogenetic analyses suggest that the C. parvum bovine genotype and C. meleagridis were originally parasites of rodents and mammals, respectively, but have subsequently expanded their host ranges, including humans. Understanding the evolution of Cryptosporidium species is important not only for clarification of the taxonomy of the parasites but also for assessment of the public health significance of Cryptosporidium parasites from animals.