Cyclospora cayetanensis is an apicomplexan protozoan parasite which has eme
rged as an important cause of epidemic and endemic diarrhea, Water-borne as
well as food-borne outbreaks have occurred, including a large number of U.
S. cases associated with raspberries imported from Guatemala. Molecular mar
kers exist for tracing the epidemiology of many of the bacterial pathogens
associated with water-borne or food-borne diarrhea, such as serotyping and
pulsed-field electrophoresis, However, there are currently no molecular mar
kers available for C. cayetanensis. The intervening transcribed spacer (ITS
) regions between the small- and large-subunit rRNA genes demonstrate much
greater sequence variability than the small-subunit rRNA sequence itself an
d have been useful for the molecular typing of other organisms. Thus, ITS1
variability might allow the identification of different genotypes of C. cay
etanensis. In order to determine the degree of ITS1 variability among C. ca
yetanensis isolates, the ITS1 sequences of C. cayetanensis isolates from a
variety of sources, including raspberry-associated cases, cases from Guatem
ala, and pooled and individual isolates from Peru, were obtained. The ITS1
sequences of all five raspberry-associated isolates were identical, consist
ent with their origin from a single source, In contrast, one of the two Gua
temala isolates and two Peruvian isolates contained multiple ITS1 sequences
, These multiple sequences could represent multiple clones from a single cl
inical source or, more likely, variability of the ITS1 region within the ge
nome of a single clone.