Cyclospora’s Mode of Infection
The modes of transmission of C. cayetanensis are still not completely understood. Direct person-to-person transmission is unlikely because the oocysts are not infectious when initially shed (unlike Cryptosporidium, another foodborne parasite).
Individuals with Cyclospora infection excrete unsporulated oocysts in their feces. These oocysts require 7 to 15 days to sporulate under ideal conditions (23-27°C or 73-81ºF) and only then become infectious to a susceptible host. Therefore, food or water contaminated with freshly excreted Cyclospora oocysts is not likely to cause an infection; rather C. cayetanensis requires weeks to sporulate in the environment to become infectious. Indirect transmission can occur if an infected person contaminates the environment, the oocysts sporulate under the right conditions, and then contaminated food and water are ingested. The role of soil in transmission has also been proposed. The relative importance of these various modes of transmission and sources of infection is not known.
Cyclospora oocysts have been detected in non-gastrointestinal samples. There have been reports of oocysts in the sputa of HIV patients with a history of pulmonary tuberculosis, suggesting that Cyclospora could be considered an opportunistic pathogen. Travel to rural areas and ingestion of contaminated foods could be modes of infection. Accidental inhalation of oocysts has also been suggested.
The dissemination of infective Cyclospora oocysts via water, soil, and unprocessed foods (e.g., fruits and vegetables, including ready-to-eat salads) is enabled by their small size (8–10 μm), low specific gravity, and high infectivity. Such oocysts can survive for weeks to months in water and food, depending on the environmental temperature, and are resistant to the routine sanitization or chemical disinfection procedures used in irrigation systems, recreational waters, or drinking water treatment plants.