The taxonomy of Cyclospora.

To the Editor: In the article by N.J. Pieniazek and B.L. Herwaldt (1) on the rRNA gene of Cyclospora cayetanensis, the authors suggest that Cyclospora should be placed in the genus Eimeria because the rRNA genes of the two genera have similar sequences. The article refers to Norman D. Levine’s chapter on the Apicomplexa in the Illustrated Guide to the Protozoa (2). Regrettably, the authors failed to read the whole chapter and to recognize that the initial characteristics for placing the oocyst of a coccidium in its proper genus are the number of sporocysts and then the number of sporozoites in each sporocyst. The genus Eimeria has four sporocysts and two sporozoites in each sporocyst. The genus Cyclospora has two sporocysts, each of which has two sporozoites. The original taxonomists (3) of C. cayetanensis recognized that it should be placed in the taxonomic family Eimeriidae, close to Eimeria, but they adhered to the traditional designation for genera of coccidia. Pieniazek and Herwaldt should be cognizant of the rules of zoologic nomenclature as well as the fact that certain morphologic characteristics of protists have served us well for many decades and continue to be useful. There are serious consequences to changing the classification of an organism, and it should not be thought that one can make such a change casually. I encourage the editors of Emerging Infectious Diseases to seek the advice of those who understand what should be done with respect to the classification and nomenclature of organisms.