Intestinal Protozoans I - Cryptosporidium, Cyclospora cayetanensis, Cystoisospora belli

Protozaon; Apicomplexa

What is the taxonomic classification of Cryptosporidiosis spp.?

• Phylum Apicomplexa

  • Cryptosporidium hominis

  • Cryptosporidium parvum

What is the distribution of Cryptosporidiosis spp.?

Worldwide

What is the transmission route of Cryptosporidiosis spp.?

Ingestion of water, food, etc. contaminated with oocyst.

Define the initial life stage involving oocysts in Cryptosporidiosis spp..

Oocyst undergoes excystation → sporozoites are released → parasitize epithelial cells in the GI tract → develop into trophozoites

Define the life stage involving trophozites in Cryptosporidiosis spp..

They undergo asexual reproduction and produce merozoites

Define the life stage involving merozoites in Cryptosporidiosis spp..

They either

1. Reinfect epithelial cells and develop into trophozoites that continue to reproduce asexually (Type 1 Meront), or…

2. Reinfect epithelial cells and develop into Type II Meronts that will reproduce sexually

What happens after Type II meronts reproduce sexually?

The release merozoites that infect epithelial cells and develop into undifferentiated gamonts.

Define the life stage involving gamont.

They can either differentiate into…

1. Microgamont (male)

2. Macrogamont (female)

What happens after gamonts differentiate into microgamonts?

They produce microgametes, which fertilize macrogamonts to produce zygotes

Define the life stage involving zygotes.

Develop into thin-walled or thick-walled oocyst → Oocyst sporulate

What is a unique characteristic of thick-walled oocyst in Cryptosporidium spp.’s life cycle?

They are released with feces and immediately become infectious

What is a unique characteristic of thin-walled oocyst in Cryptosporidium spp.’s life cycle?

They release sporozoites in the host, continuing autoinfectious cycle

What are the host(s) involved in C. hominis?

• Definitive hosts: humans

• Reservoir hosts: none

What are the host(s) involved in C. parvum?

• Definitive hosts: mammals

• Reservoir hosts: mammals

What are some symptoms associated with Cryptosporidium spp.?

• Incubation period 2 - 10 days (avg. 7 days)

• Asymptomatic

• Diarrhea

• Immunocompromised patients: malabsorption, wasting, fever, fatigue

How would you diagnose Cryptosporidiosis?

• Microscopy

• Immunofluorescence microscopy

• Enzyme immunoassays

• PCR

How would you treat Cryptosporidiosis in healthy patients?

• Self-limiting in 2 - 3 weeks

• Fluids - drinking and IV, anti-protozoals (if needed)

How would you treat Cryptosporidiosis in immunocompromised patients?

• Dependent on multiple factors

  • HIV-infected - antiretrovirals reduce/eliminate symptoms; infection may never be cleared

What causes Cyclosporiasis in humans?

Cyclospora cayetanensis

What is the distribution of Cyclospora cayetanensis?

Worldwide, especially in tropics and subtropics

Whats is the seasonality of Cyclosporiasis?

More frequent infections in the summer and in the rainy season

What is the taxonomic classification of Cyclospora cayetanensis?

• Phylum: Apicomplexa

  • Cyclospora cayetanensis

What is the route of transmission of Cyclosporiasis?

Ingestion of water, food, etc. contaminated with C. cayetanensis oocysts

Define sporozoites in the context of C. cayetanensis.

The either develop into…

• Type I Meronts, or…

• Type II Meronts

Define Type I Meronts in the context of C. cayetanensis.

They develop release merozoites, which develop into Type I Meronts (continue asexual cycle) or Type II Meronts

Define Type II Meronts in the context of C. cayetanensis.

Invade epithelial cells → Develop into macro- and microgametocytes -→ Reproduce sexually and produce zygotes -→ Develop into oocyst

How are oocysts unique in the life cycle of C. cayetanensis?

The are not immediately infection; sporulate in environments after days to weeks at 22 C - 32 C

Define oocyst after sporulation in the context of C. cayetanensis.

Oocyst has two sporocysts, each with two sporozoites

Describe symptoms associated with Cyclosporiasis in humans.

• Incubation period: 7 days

• Asymptomatic

• Diarrhea, dysentery

• Other abdominal symptoms, some non-specific

• Weight loss

• More severe in immunocompromised patients

How would you diagnose Cyclosporiasis?

• Microscopy, with or without acid-fast staining

• Antigen tests

• PCR

How would you treat Cyclosporiasis?

Healthy patients:

• Self-limiting in 10-12 weeks

• Fluids - drinking and IV, antibiotic if needed

• Supportive

• Can relapse if untreated

Immunocompromised patients:

• Antibiotic

• Supportive if allergic to antibiotic

What is the causative agent for Cystoisosporiasis in humans?

Cystoisospora belli

What is the distribution of Cystoisospora belli?

Worldwide, especially in tropics and subtropics

What is the route of transmission of C. belli?

Ingestion of water, food, etc. contaminated with C. belli oocysts

What happens after C. belli oocyst are ingested?

They travel to the small intestines, excyst, and release sporozoites

Define asexual reproduction in the context of C. belli?

Sporozoites invade epithelial cells → Sporozoites begin schizogony (asexual reproduction) ^→ Schizonts rupture & release merozoites → Merozoites infect new epithelial cells and continue asexual reproduction

Define sexual reproduction in the context of C. belli?

Merozoites invade epithelial cells → develop into gametocytes → Male gametocytes produce microgametes → Microgametes join with macrogamete to produce oocyst (passed through feces)

What is unique about oocyst in the context of C. belli?

Immature; NOT immediately infectious

Define sporoblast in the context of C. belli.

They are differentiated oocyst that later mature into sporocyst → produce 4 sporozoites → oocysts become infectious

What are the host involved in the transmission of C. belli?

• Definitive hosts: humans

• Reservoir hosts: none

What are symptoms associated with Cystoisosporiasis?

• Incubation period 7 days

• Asymptomatic

• Diarrhea, abdominal cramps, nausea, vomiting, fever

• Malabsorption

• Weight loss

• More severe in immunocompromised patients

How would you diagnose Cystoisosporiasis?

• Microscopy, with or without acid-fast staining

• Biopsy

How would you treat Cystoisosporiasis?

Healthy patients:

• Fluids - drinking and IV, antibiotics if needed

Immunocompromised patients:

• Antibiotics