Submitted to: International Meeting on Molecular Epidemiology and Evolutionary Genetics in Infectious Disease
Publication Type: Abstract Only
Publication Acceptance Date: 5/16/2002
Publication Date: 7/25/2002
Citation: Fayer, R., Ryan, U., Lihua, X., Upton, S., Thompson, A., Lal, A. 2002. Genetic, Biochemical, and Biological Factors to consider when naming new species of Cryptosporidium. [Meeting Abstract].International Meeting on Molecular Epidemiology and Evolutionary Genetics in Infectious Disease, July 15-19, 2002, Paris, France.
Technical Abstract: Genetic analyses of Cryptosporidium oocysts recovered from humans have indicated that most cases of cryptosporidiosis are caused by two distinct organisms previously referred to as the "human" genotype (genotype 1 or genotype H) and the "cattle" genotype (genotype 2 or genotype C). Isoenzyme analyses, PCR-RFLP, and sequence analyses of many unlinked loci from various geographic locations have identified consistent genetic differences between these 2 organisms. They also differ biologically. Although a neonatal gnotobiotic pig model has been established for the "human" genotype, this genotype is not infectious for mice or cattle. In contrast, surveys and experimental transmission studies have shown that the "cattle" genotype is transmissible to a wide range of hosts. Furthermore, recent pathogenicity studies have revealed distinct differences between the human and cattle genotypes. Based on the aforementioned findings it has been proposed that the `human' genotype be considered a species separate from C. parvum and that it be identified by the name Cryptosporidium hominis. As more evidence of differences among isolates of Cryptosporidium becomes available the decisions to name these isolates new species becomes more complex. What are the rules governing the naming of new species and how do they apply to morphologically identical organisms? What genes should be selected as a basis for speciation? How many base pair differences are needed to suggest an isolate is a different species? What isoenzymes should be examined for differences? What biological features reflect species level differences? What animal hosts should be tested in cross transmission studies for infectivity? These important questions should be addressed by the panel of experts and expressed as a paper resulting from this international conference.