Cyclospora cayetanensis

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Microbiology in Italy[1]

Etiology/Bacteriology

Taxonomy

| Domain = Eukaryota | Phylum = Apicomplexa | Class = Coccidia | Order = Eucoccidiorida | Family = Eimeriidae | Genus = Cyclospora | species = C. cayetanensis

NCBI: [2]

Pathogenesis

Transmission

Cyclospora cayetanensis is spread via the fecal-oral route, meaning that the host must ingest something, food or water for example, that had been contaminated with infectious oocysts present in feces. The oocysts take from days to weeks outside a host cell after being excreted in a fecal matter to become a sporulated oocyst capable of infection of another host. 2 Contaminated food including imported fresh produce form tropical regions, such as raspberries, basil and lettuce have caused outbreaks of cyclosporiasis and oocysts were effectively transmitted to the host. 3 Essentially, any food that has been contaminated with fecal matter containing sporulated infectious oocysts have the potential to cause infection of Cyclospora cayetanensis. To date, there has been no documented transmission from human-to-human. 5

Virulence factors

Cyclospora cayetanensis infects the epithelial cells that line the small intestine using several mechanisms, however much is still not known about this parasites virulence factors and characteristics used to infected the host. Of course it is known that several requirements are needed for a parasite to cause disease in a host, and without these, the parasite would not be able to invade the host. These requirements include the ability for the organism’s infectious form, and in the case of Cyclospora , its oocyst, to survive in harsh environmental conditions. The oocyst has a thick bilayered wall, allowing the organism to be environmentally resistant and able to survive until ingestion of a host. 10 This characteristic help the oocyst to survive a chlorination process of water, leaving it still contaminated by the pathogen. Another helpful feature of the mature oocysts contributing to pathogenesis is its fibrillar coat, which is also seen in the noninfectious, unsporulated oocysts that are in the stool of infected hosts. 10 This fibrillar coat is thought to help the parasite adhere to the foods it is known to contaminate, like the basil leaf or raspberries.

Diagnosis

The first step in diagnosis of Cyclospora cayetanensis infection should be when health care providers notice the symptom of prolonged diarrhea in the patient, and should also look at the other symptoms associated with the disease as well. If the patient has recently traveled to a tropical or sub-tropical area that is known for causing infection, the healthcare provider should ask the patient for a stool sample 3 However, because testing for Cyclospora is not usually done in most laboratories in the US when the stool is tested for parasites, identification for C. cayetanensis in the stool requires special lab tests not routinely done, therefore this microorganism can be difficult to diagnose, especially when it comes to laboratory tests. This is because even if an infected patient is symptomatic, there may not be enough oocysts in the stool to detect infection in lab examinations; therefore it is not uncommonly needed for the patient to provide multiple stool specimens ranging within several days. 2 Identification of this organism can be made through microscopic techniques, usually several different stains, such as Acid-fast stains, or using an epifluorescence microscope, in which the the Cyclospora oocyst appear a neon-blue color. 1 Due to the face that Cyclospora cayetanensis is unable to be culture in the laboratory and its small size, it is near impossible to detect and isolate the organism on the contaminated food since the amount of organisms on it are so low. 3

Treatment

The specific drug treatment for disease caused by Cyclospora cayetanensis is the combination of two antibiotics—trimethoprim and sulfamethoxazole (co-trimaxazole), which are also sold under the names of Bactrim, Cotrim, or Septra, and symptoms can diminish within the next several days. 8 Unfortunately, there have been no alternative drug treatment options that have been effective for patients that suffer from a sulfa allergy or do not respond to the combination antibiotic. 2 Of course anti-diarrheal medication can be given by a health care provider to reduce the diarrheal symptom, but this does not actually combat against the microorganism. Hydration and rest are also essential to patients with diarrhea, and in most healthy individuals the infection can be self-limiting, and most can recover in a few days, or possibly a month or longer. 2 If left untreated the protracted diarrhea can lead to severe dehydration, and in cases like these hospitalization may occur.