Although outbreaks of Cyclospora cayetanensis have occurred worldwide including the U.S., this organism is endemic in South and Central America, parts of Asia, Africa, Southern Europe, and the Middle East. Outbreaks have been associated with contaminated food or water; in the U.S., they have often been associated with imported contaminated fruits or vegetables. Person-to-person transmission is unlikely.
The infection is acquired through the fecal-oral route (see life cycle below).
Some patients are asymptomatic; others have a flu-like illness, nausea, vomiting and explosive diarrhea lasting up to three weeks.
This organism does not stain well with the trichrome stain. It can be concentrated and stained with a special stain such as the modified acid-fast stain (see the section on Cryptosporidium). If acid fast structures are seen, they should be measured because C. cayetanensis is approximately twice the size of Cryptosporidium: 8-10 μm vs. 4-6 μm (image on right). Multiple stool samples should be examined before concluding that the patient is negative for this organism.
A very interesting characteristic is that the oocysts of C. cayetanensis auto-fluoresce under UV light!
Other diagnostic methods that have been developed but are not commonly used include flow cytometry and molecular methods.
