Cyclospora cayetanensis is a significant coccidian parasite that primarily infects humans, causing gastrointestinal issues in both immunocompetent and immunocompromised individuals. It spreads through ingestion of contaminated water or produce, with characteristic symptoms including diarrhea, fatigue, and weight loss, particularly in AIDS patients. Diagnosis typically involves microscopic detection of oocysts in stool samples, and treatment is effectively managed with trimethoprim-sulfamethoxazole.

1. COCCIDIAN PARASITES
Cyclospora cayetanensis
Dr. Suprakash Das
Assit. Prof.

2. Cyclospora cayetanensis
 C. caytanensis is the only species of the genus that is cause to
infection in human.
 Infection of GI tract in both immunocompetent and
immunocompromised hosts.
 First discovered in 1979 in the human faeces, it has become an
important parasite for AIDS patients.
 During the past few years, there have been several outbreaks of
diarrhea associated with C. cayetanensis; the distribution is
worldwide (United States, Caribbean, Central and South America,
Southeast Asia, Eastern Europe, Australia, Nepal).

3. Morphology
Diagnostic forms in
humans
Cyclospora oocyst- these are excreted in the human
faeces. These are round to oviod structures and measures
8-10 µm in diameter, variably Acid-fast and has blue-
green flourescence.
 Sporulating oocyst- It is the Infective form to humans.
Each oocyst contains 2 Sporocysts, each measuring 4
µm in diameter and containing 2 Sporozoites.

5. Life Cycle
 Humans acquire infection by the ingestion of water or
vegetables contaminated with the sporulating oocyst-
each oocyst contain 4 sporozoites.
 In the intestine, the oocyst releases sporozoites, which
invade the enterocytes.
 Multiple fission by the sporozoites inside enterocytes
produce Meronts which in turn are developed to
Merozoites.
 Two types of Meronts and sexual stages have been seen in
jejunal enterocytes

6. Life Cycle
 Merozoites divide to form Macrogametes (Female form) and
Microgametes ( Male form) and reproduce to form new oocyst.
 It takes approximately 5 days or more for oocyst maturation, so
the mature stage may not have been seen in human specimens.
 Also, information on potential reservoir hosts has yet to be
defined; however, it appears that in some areas the human is
the only host.
 Small intestine shows acute and chronic inflammation , blunting
and atrophy of villi, and hyperplasia of crypts.

9. Clinical Features
 Developmental stages of C. cayetanensis usually occur within
epithelial cells of the jejunum and lower portion of the duodenum.
 Cyclospora infection reveals characteristics of a small bowel
pathogen, including upper gastrointestinal symptoms,
malabsorption of d-xylose, weight loss, and moderate to marked
erythema of the distal duodenum.
 Histopathology in small bowel biopsy specimens reveals
 Acute and chronic inflammation,
 Partial villous atrophy,
 Crypt hyperplasia.

10. Clinical Features
The incubation period is approximately 2 to 11
days after exposure.
 There is generally 1 day of malaise and low-
grade fever, with rapid onset of diarrhea of up
to seven stools per day.
 There may also be fatigue, anorexia, vomiting,
myalgia, and weight loss with remission of self-
limiting diarrhea in 3 to 4 days, followed by
relapses lasting from 4 to 7 weeks.

11. Clinical Features
 In patients with AIDS, symptoms may persist for as long as
12 weeks; biliary disease has also been detected in this group.
 Diarrhea alternating with constipation has also been
reported.
 Clinical clues include unexplained prolonged diarrheal
illness during the summer in any patient and in persons
returning from tropical areas.
 The majority of infected individuals had intermittent
diarrhea for 2 to 3 weeks, and many complained of intense
fatigue, as well as anorexia and myalgia, during the illness.
 The clinical presentation of patients infected with this
organism is similar to that of patients infected with
Cryptosporidium.

12. Epidemiology
WORLD
It is found in warm climates, mainly the tropics
and subtropics. It is endemic in Nepal, Peru,
Haiti, with a seasonal predominance in Rainy
or Summer months. It is now also prevalent in
Peurto Rico, Mexico, Indonesia, Morocco.
INDIA
Sporadiac cases are reported from Vellore,
Puducherry, New Delhi and Benguluru.

13. Epidemiology
 Reservoir, Source and Transmission
Human are the only reservoir of infection.
Sporulating oocysts are infective stages.
Water or vegetables, Fruits like Raspberries
that are contaminated with sporulating
oocysts are the sources of infection.

16. Diagnosis
Parasitic Diagnosis-
It is based on the –
1] Direct wet mount microscopic detection of ooocyst in
faecal specimen.
2] Phase contrast microscopy
3] Autoflurescence with UV lights
4] Acid-fast staining methods.
5] LPCB mount
 The Cyclospora oocysts are excreted intermediately and in
small numbers , so at least 2-3 stool specimens at 2-3 days
interval is necessary to detect positive cases.

17. Diagnosis
Formalin-ethyl acetate sedimentation
technique and Sheather’s sucrose flotation
methods are frequently used to concentrate the
oocyst in the stool.
Molecular method- A nested PCR assay
tergetting the small sub-unit ribosomal RNA is
employed for the diagnosis of Cyclospora
infection.( 62% sensitivity).

18. Cyclospora cayetanensis oocyst in wet mount

19. Cyclospora cayetanensis oocysts
Modified acid-fast stain (A),
Differential interference contrast microscopy of wet mount
(B),
Epifluorescence microscopy (330–380 nm ultraviolet
excitation filter) (C).

20. Treatment
Trimethoprim-sulfamethoxazole (TMP-
SMZ) has proven effective in treating
cyclospora infection.
Dose- A combination of 160 mg TMP & 800
mg of SMZ 3 times/week.
Oral rehydration as a supportive treatment.