Cyclospora cayetanensis - Classification, Morphology, Culture, Life Cycle, Clinical Manifestation

Introduction of Cyclospora cayetanensis

Cyclospora cayetanensis is the only species of the genus Cyclospora known to cause infection in humans called cyclosporiasis. The parasite, which is coccidian, causes infection of the gastrointestinal (GI) tract.

Classification of Cyclospora cayetanensis

Classification of Cyclospora cayetanensis is done by:

Domain: Eukaryota

(unranked): SAR

(unranked): Alveolata

Phylum: Apicomplexa

Class: Conoidasida

Subclass: Coccidiasina

Order: Eucoccidiorida

Suborder: Eimeriorina

Family: Eimeriidae

Genus: Cyclospora

Species: C. cayetanensis

History of Cyclospora cayetanensis

Historically, Cyclospora cayetanensis was first described in 1979 and was obtained from human faeces. It mostly causes infection in both immunocompetent as well as immunocompromised (HIV patients) hosts.

Habitat of Cyclospora cayetanensis

Cyclospora cayetanensis infects and inhabits the small intestine in man.

Morphology of Cyclospora cayetanensis

The morphological forms of Cyclospora cayetanensis are described below.

Diagnostic form in humans

Oocysts

• Cyclospora cayetanensis oocysts are excreted in human faeces

• round to oval in shape

• measures 8 μm to 10 μm in diameter

• are variably acid-fast

• under fluorescence microscopy, fluorescence blue-green is seen

Infective form

Sporulating oocyst

• sporulating oocysts are infectious forms of Cyclospora cayetanensis in humans

• each oocyst contains two sporocysts

• each sporocyst measures 4μm in diameter

• each sporocyst contains four sporozoites

Life Cycle of Cyclospora cayetanensis

• humans get infected with Cyclospora cayetanensis after ingestion of water or food contaminated with sporulating oocysts

• these oocysts after reaching the intestine release the sporozoites

• the newly released sporozoites invade the enterocytes where they develop into unsporulated oocysts

• the unsporulated oocysts are excreted in faeces

• these oocysts undergo sporulation under favourable conditions in the environment- outside the host body

• ingestion of the sporulated oocysts causes infection in susceptible hosts and the life cycle of Cyclospora cayetanensis is repeated

Pathogenesis, Pathology of Cyclospora cayetanensis

The host small intestine shows pathological changes such as acute inflammation, chronic inflammation, blunting and atrophy of villi, hyperplasia of crypts, etc.

Clinical Manifestation of Cyclospora cayetanensis

• clinical syndromes of Cyclospora cayetanensis are similar to that of isosporiasis and cryptosporidiosis

• the incubation period ranges from 1 day to 14 days

• other symptoms include abdominal pain, nausea, vomiting, malaise, low-grade fever, myalgias

• in rare cases, clinical syndromes such as anorexia, bloating, flatulence, and fatigue are observed

• the key clinical feature is diarrhoea and its course depends upon whether the host is immunocompromised or immunocompetent

• in immunocompetent individuals, diarrhoea may last for several weeks to 2 weeks, self-limited, with a waxing and waning course

• in an immunocompromised host, the onset of diarrhoea is insidious, watery, and profuse

  in prolonged diarrhoea, dehydration, and loss of weight may occur, which might eventually lead to chronic diarrhoea with oocysts released in the faeces

Complications of Cyclospora cayetanensis

In patients with AIDS, Cyclospora cayetanensis infection is associated with the biliary disease with right upper quadrant pain.

Prognosis of Cyclospora cayetanensis

• mortality by Cyclospora cayetanensis infection is rare and has a good prognosis

• in immunocompromised hosts, morbidity occurs due to chronic diarrhoea