aEntamoeba histolytica is used to designate the true pathogenic species, while E. dispar is now being used to designate the nonpathogenic species. However, unless trophozoites containing ingested red blood cells (E. histolytica) are seen, the two organisms cannot be differentiated on the basis of morphology seen in the permanent stained smears of fecal specimens. Fecal immunoassays are available for detecting the E. histolytica/E. dispar group or for differentiating the two species.
bAlthough some individuals have changed the species designation for the genus Giardia to G. intestinalis or G. duodenalis, there is no general agreement. Therefore, for this listing, the name Giardia lamblia will be retained.
cThis designation is not a true genus, but a “catch-all” for those organisms that have not been (or may never be) identified to the genus and/or species levels. However, it is now listed as one of the genera of microsporidia infecting humans.
dSee the section on arthropods, below.
Table 2.2 Cosmopolitan distribution of common parasitic infections (North America, Mexico, Central America, South America, Europe, Africa, Asia, and Oceania)
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