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Cyclospora cayetanensis in a modified acid-fast stained smear of diarrhoeal stool

Cyclospora cayetanensis in a modified acid-fast stained smear of the diarrhoeal stool as shown above picture that causes Cyclosporiasis.

Introduction of Cyclospora cayetanensis

Cyclospora cayetanensis is a coccidian parasite that causes diarrheal disease in humans. C. cayetanensis has since emerged as an endemic cause of diarrheal disease in tropical countries and a cause of traveler’s diarrhea and food-borne infections in developed nations. They had sporulated and excysted the oocysts, resulting in the placement of the parasite in the genus Cyclospora. The specific name refers to the Cayetano Heredia University in Lima, Peru, where early epidemiological and taxonomic work was performed.

Scientific Classification of Cyclospora cayetanensis

• Domain: Eukaryota
• Phylum: Apicomplexa
• Class: Conoidasida
• Subclass: Coccidiasina
• Order: Eucoccidiorida
• Suborder: Eimeriorina
• Family: Eimeriidae
• Genus: Cyclospora
• Species: C. cayetanensis
• Binomial name: Cyclospora cayetanensis

Morphology of Cyclospora cayetanensis

Cyclospora cayetanensis is an apicomplexan, cyst-forming coccidian protozoan that causes self-limiting diarrhea. In terms of morphology, It has spherical oocysts that are between 7.5 and 10 μm in diameter that also have a 50-nm-thick wall with an outer thread-like coat. The oocyst formula is O.2.2 which means one oocyst contains two sporocysts and each sporocyst contains two sporozoites.

Life cycle of Cyclospora cayetanensis

Humans are the only confirmed hosts for Cyclospora cayetanensis . The protozoan lives out its life cycle intracellularly within the host’s epithelial cells and gastrointestinal tract. Infection is transmitted through the fecal-oral route and begins when a person ingests oocysts in feces-contaminated food or water. Various chemicals in the host’s gastrointestinal tract cause the oocysts to excyst and release sporozoites; generally, two are observed per oocyst. After these sporozoites invade the epithelial cells, they undergo merogony, a form of asexual reproduction that results in many daughter merozoites. These merozoites may either infect new host cells and initiate yet another round of merogony or take on a sexual track via gametogony: Daughter merozoites become male macrogamonts that form many microgametes and female macrogamonts. After fertilization has occurred through male microgamete fusion with female macrogamont, the zygote matures into an oocyst and ruptures the host cell, from which point it is passed with the stool. The oocysts that are passed are not, however, immediately infectious. Sporulation can take from one to several weeks, meaning person-to-person transmission is not a likely problem.

Symptoms of Cyclosporiasis

C. cayetanensis causes gastroenteritis, with the extent of the illness varying based on age, condition of the host, and size of the infectious dose. Symptoms include –

• watery diarrhea,
• loss of appetite,
• weight loss,
• abdominal bloating
• and cramping,

increased flatulence, nausea, fatigue, and low-grade fever”, though this can be augmented in more severe cases by vomiting, substantial weight loss, excessive diarrhea, and muscle aches.

Note: Human cyclosporiasis is clinically similar to cryptosporidiosis, isosporiasis, giardiasis, and microsporidiosis because of the similar clinical features.

Risk factors of Cyclosporiasis

• Persons living or traveling in developing tropical or subtropical areas may be at an increased risk of acquiring Cyclosporiasis.
• Consuming food or water while visiting developing countries is a well-documented way of developing traveler’s diarrhea. Since oocysts are shed in the feces of infected persons and then must mature in the environment 2–14 days before they can become infectious, it is unlikely for a person to get an infection directly from another person, such as an infected food handler.

Lab Diagnosis of Cyclospora cayetanensis

Due to being smaller in size, intracellular habitat, and inability to properly take up many histological stains and therefore, diagnosis of C. cayetanensis can be very difficult. Methods of detection-

• Microscopic detection in stool samples of oocysts; recovering oocysts in intestinal fluid or small bowel biopsy specimens
• Detection of genes of oocyst sporulation and amplification by polymerase chain reaction (PCR) of C. cayetanensis.
• phase-contrast microscopy to check for the spherical oocysts
• modified acid-fast staining to check for variable staining from pale to red

Note: Fecal exams to identify oocysts, centrifuging a sample of feces in a sucrose solution, and then transferring a small amount to a slide were found to be remarkably effective.

Since detection is so hard, one negative result should not discount the possibility of C. cayetanensis: tests involving fresh stool samples over the next few days should also be considered.

Treatment of Cyclosporiasis

The most effective drug for the treatment of protozoan is a seven-day course of oral trimethoprim-sulfamethoxazole (TMP-SMX).

Prevention of Cyclosporiasis

No vaccine against this C. cayetanensis, the pathogen is available. The simplest is way to warn travelers not to visit regions where the protozoan is endemic especially when the season is best for spreading:

• Travelers also should be aware that treatment of water or food with chlorine or iodine is unlikely to kill Cyclospora oocysts.
• Better health practices in the originating agricultural setting—such as making sure produce watering systems are not pulling water that has access to human feces.
• Adopting filtering systems such as a 1-micron absolute carbon filtration system will reduce the presence of Cyclospora, drastically decreasing the incidence of the spread of this parasite.
• Only eat thoroughly washing fruits and vegetables in clean water prior to consumption.

Bibliography

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2806662/
2. https://www.kstate.edu/parasitology/cyclospora/cyclospora.html
3. file:///C:/Users/Berry/Downloads/3285-Article%20Text-12072-1-10-20100730%20(1).pdfhttps://www.cdc.gov/parasites/cyclosporiasis/biology.html
4. https://www.cdc.gov/parasites/cyclosporiasis/disease.html
5. https://www.researchgate.net/publication/230636408_Human_Infection_of_Cyclospora_cayetanensis_A_Review_on_its_Medicobiological_and_Epidemiological_Pattern_in_Global_Scenario