L6: Other Protozoans: Coccidians

To which phylum do coccidians belong?

Phylum Apicomplexa.

What are the general characteristics of coccidians?

Spore-forming, microscopic, single-celled, obligate intracellular protozoans.

Which organ system do coccidians primarily infect?

The gastrointestinal (GI) tract.

What disease is caused by coccidians?

Coccidiosis

What is the clinical significance of coccidian infections in immunocompetent individuals?

They are usually asymptomatic.

What is the clinical significance of coccidian infections in immunocompromised individuals?

They can cause severe, opportunistic infections.

What are the three main stages of the coccidian life cycle?

Gametogony, Sporogony, and Schizogony/Merogony.

What occurs during gametogony?

Development of microgametocytes and macrogametocytes.

What occurs during sporogony?

It is the sexual cycle that results in the production of oocysts.

What occurs during schizogony (merogony)?

It is the asexual cycle that results in the production of merozoites

What are the key methods of prevention and control of coccidian infections?

Good sanitation, adequate water treatment, and proper washing of fruits and vegetables.

Why is chlorination ineffective against coccidians?

Their oocysts are resistant to chlorination.

What is the most effective way to treat water contaminated with coccidian parasites?

Boiling the water.

Where is Cystoisospora belli commonly found?

In tropical countries with poor sanitation.

Which populations are at higher risk for Cystoisospora belli infection?

Infants, individuals in daycare centers, and those in mental institutions.

What is the transmission mode of Cystoisospora belli?

Ingestion of mature (sporulated) oocysts.

How many sporocysts and sporozoites are found in a Cystoisospora belli oocyst?

2 sporocysts, each containing 4 sporozoites (total: 8 sporozoites).

Where does Cystoisospora belli reside in the human body?

Distal duodenum and proximal ileum.

What are the clinical manifestations of Cystoisospora belli infection?

Diarrhea, anorexia, fever, vomiting, weight loss, and body malaise.

What are the severe symptoms of Cystoisospora belli infection?

Prolonged diarrhea, fat malabsorption, and dissemination to other organs.

How is Cystoisospora belli diagnosed?

Visualization of oocysts in stool using direct fecal smear, concentration techniques, or acid-fast staining, phenol-auramine staining, iodine staining, entero-test (String capsule test), duodenal aspirate

What is the treatment for Cystoisospora belli infection?

Trimethoprim-Sulfamethoxazole (160/800 mg QID for 10 days).

Which countries have reported Cyclospora cayetanensis infections?

Nepal, Peru, Haiti, and the United States.

Which food items have been linked to Cyclospora cayetanensis outbreaks?

Raspberries, lettuce, and basil pesto salad.

What was Cyclospora cayetanensis originally called?

Cyanobacterium-like body (CLB).

What is the transmission mode of Cyclospora cayetanensis?

Ingestion of mature (sporulated) oocysts.

How many sporocysts and sporozoites are found in a Cyclospora cayetanensis oocyst?

2 sporocysts, each containing 2 sporozoites (total: 4 sporozoites).

Where does Cyclospora cayetanensis reside in the human body?

The jejunum.

What are the symptoms of Cyclospora cayetanensis infection?

Alternating diarrhea and constipation, D-xylose malabsorption.

How is Cyclospora cayetanensis diagnosed?

Visualization of oocysts in stool using direct fecal smear, acid-fast staining, PCR, or fluorescent microscopy.

What is the treatment for Cyclospora cayetanensis infection?

Trimethoprim-Sulfamethoxazole (160/800 mg BID for 7 days).

What are the two species of Cryptosporidium that infect humans?

Cryptosporidium parvum and Cryptosporidium hominis.

What is the main mode of transmission for Cryptosporidium?

Ingestion of thick-walled oocysts from contaminated water.

How many sporocysts and sporozoites are in Cryptosporidium oocysts?

0 sporocysts, 4 sporozoites.

What are the symptoms of cryptosporidiosis?

Prolonged watery diarrhea, malabsorption, and wasting.

What are the extra-intestinal manifestations of cryptosporidiosis?

Pneumonia, cholecystitis, and conjunctivitis.

How is Cryptosporidium diagnosed?

Modified acid-fast staining, Sheather’s sugar flotation, or enzyme immunoassays.

What is the treatment for Cryptosporidium infection?

Nitazoxanide

What is the definitive host of Toxoplasma gondii?

Cats

What are the intermediate hosts of Toxoplasma gondii?

Pigs, rats, sheep, and birds.

How can humans acquire Toxoplasma gondii infection?

Ingesting sporulated oocysts, eating undercooked meat with bradyzoites, blood transfusion, organ transplantation, or transplacental transmission.

What is the classic triad of congenital toxoplasmosis?

Hydrocephalus, intracranial calcifications, and chorioretinitis.

What is the most sensitive test for diagnosing Toxoplasma gondii?

Sabin-Feldman dye test.

What is the treatment for Toxoplasma gondii infection?

Pyrimethamine + Sulfadiazine + Folinic Acid.

Consuming contaminated food or water (Taxoplasma gondii infective stages, human)

Sporulated oocyst

Eating raw or undercooked meat (Taxoplasma gondii infective stages, human)

Encysted bradyzoites

Blood transfusion (Taxoplasma gondii infective stages, human)

Tachyzoites

Transplacental infection (Taxoplasma gondii infective stages, human)

Tachyzoites

Organ transplantation (Taxoplasma gondii infective stages, human)

Tachyzoites and bradyzoites

Infective stage of sarcocystosis in intestinal form

Ingestion of sarcocyst with bradyzoites

Infective stage of sarcocystosis in muscular/invasive form

Ingestion of oocyst or sporocyst