Cyclospora cayetanensis, a food- and waterborne coccidian parasite.
Food- and waterborne coccidia including Cryptosporidium parvum, Cyclospora cayetanensis, Sarcocystis hominis and Sarcocystis suihominis, and Isospora belli are cyst-forming apicomplexan protozoa that cause intracellular infections, predominantly in the epithelial cells of the intestine. They are transmitted by oocysts from person-to-person by the fecal-oral route or via contaminated water or food. The most common symptom of infection is diarrhea, however, asymptomatic infections occur. Infections are associated with intestinal inflammation, with pathological lesions such as villus blunting, and abnormal function such as malabsorption. Mild-to-moderate, self-limiting diarrhea is common in healthy individuals ingesting infective stages of these organisms. However, patients with immune dysfunction can have severe intestinal injury and prolonged diarrhea. Diagnosis in many cases is made by a microscopic examination of the stool, and the use of appropriate staining techniques, but more recently molecular methods for detection are used increasingly. Effective antimicrobial treatment for prolonged infection in immunocompromised patients is available for most of these infections. These gastrointestinal coccidial pathogens have important similarities in epidemiology, disease pathogenesis, clinical manifestations, diagnosis, and treatment. Although there are many other cyst-forming coccidia of public health, veterinary and/or economic importance, discussion in this chapter will be limited to C. cayetanensis, as an important example of the group. Aspects of the biology, epidemiology, diagnosis, disease, treatment and control are considered. This parasite is considered to be an emerging pathogen. From 1990 to 2000, there were 11 foodborne outbreaks of cyclosporosis in North America that affected at least 3600 people. There are many outstanding questions regarding this parasite and under-reporting is common because general diagnostic methods for intestinal parasites are inadequate for detection of Cyclospora.