Other Protozoan: Coccidian

Thick-walled oocyst containing 4 sporozoites

What is the infectious stage of Cryptosporidium hominis?

Cryptosporidium spp. Thin-walled oocyst

Cause autoinfection

Thick-walled oocysts

Are excreted and infect new hosts

It remains intracellular but extracytoplasmic, attaching to the brush border of enterocytes.

How does Cryptosporidium attach to the intestinal epithelium?

Fecal-oral route

What is the primary route of transmission for Cryptosporidium hominis?

Modified Acid-Fast Stain

What is the most common stain used to detect Cryptosporidium oocysts?

Nitazoxanide

What is the treatment for Cryptosporidium infection?

Cryptosporidium hominis

A 34-year-old HIV-positive man presents with profuse watery diarrhea, weight loss, and dehydration. He recently drank tap water in an underdeveloped country. A stool sample reveals acid-fast oocysts measuring 4-5 µm. What is the most likely causative agent?

The patient is likely immunocompromised, and the parasite is causing autoinfection via thin-walled oocysts.

A patient with persistent watery diarrhea undergoes stool analysis, which reveals numerous acid-fast positive oocysts. What is the likely explanation if symptoms persist despite treatment?

Oocysts have a thick outer wall that is resistant to standard chlorine levels. Filtration is required for removal.

Why is chlorination alone not sufficient to kill Cryptosporidium oocysts in drinking water?

Sporulated oocyst containing 2 sporocysts with 2 sporozoites each

What is the infectious stage of Cyclospora cayetanensis?

Cyclospora oocysts are unsporulated and require days to weeks to become infectious, unlike Cryptosporidium, which is immediately infectious.

What is the key difference between Cyclospora and Cryptosporidium oocysts upon excretion?

Jejunum (small intestine)

Where does Cyclospora infect in the human body?

Watery diarrhea, anorexia, weight loss, nausea, vomiting, bloating, fatigue

What are the common symptoms of Cyclospora infection?

Contaminated fresh produce such as raspberries, lettuce, and basil

What are common sources of Cyclospora outbreaks?

Trimethoprim-Sulfamethoxazole (TMP-SMX)

What is the treatment for Cyclospora infection?

Autofluorescent, appearing blue or green depending on the filter.

How do Cyclospora oocysts appear under a fluorescent microscope?

Cyclospora cayetanensis infection (Cyclosporiasis)

A 28-year-old tourist returns from a trip to Nepal with prolonged watery diarrhea, fatigue, and bloating. He reports eating fresh salads and drinking untreated water. A modified acid-fast stain of his stool reveals variably acid-fast oocysts. What is the most likely diagnosis?

Oocysts require time to sporulate after excretion, meaning contamination likely occurred during harvesting, washing, or packaging rather than direct person-to-person transmission.

Why do Cyclospora outbreaks often occur in association with imported produce?

Cyclospora is not responsive to ciprofloxacin. The correct treatment is Trimethoprim-Sulfamethoxazole (TMP-SMX).

A patient with prolonged diarrhea is prescribed ciprofloxacin, but his symptoms persist. What is the most likely explanation?

Sporulated oocyst containing 2 sporocysts with 4 sporozoites each

What is the infectious stage of Cystoisospora belli?

Small intestine (duodenum and jejunum)

Where does Cystoisospora belli infect in the human body?

Watery diarrhea, malabsorption, weight loss, eosinophilia

What are the common symptoms of cystoisosporiasis?

Large and oval (20–33 µm), staining red

How do Cystoisospora oocysts appear in a modified acid-fast stain?

Trimethoprim-Sulfamethoxazole (TMP-SMX)

What is the drug of choice for treating Cystoisospora infection?

AIDS patients, immunocompromised individuals, and malnourished individuals

What populations are at higher risk for severe cystoisosporiasis?

Cystoisospora belli

A 45-year-old man with HIV/AIDS presents with chronic watery diarrhea, weight loss, and eosinophilia. A modified acid-fast stain of his stool reveals large, oval, acid-fast oocysts measuring 20–30 µm. What is the most likely causative agent?

Tachyzoite, Bradyzoite, Oocyst

What are the three infective stages of Toxoplasma gondii?

Cats (family Felidae)

What is the definitive host of Toxoplasma gondii?

Intestinal epithelium of cats

Where does the sexual cycle of Toxoplasma gondii occur?

Tachyzoites

Rapidly multiplying, found in acute infection

Bradyzoites

Slow-growing, found in chronic infection within cysts

1. Ingesting oocysts from cat feces (contaminated food, water, or soil)

2. Eating undercooked meat containing bradyzoite cysts

3. Congenital transmission from mother to fetus

4. Organ transplantation or blood transfusion

How does a human become infected with Toxoplasma gondii?

Brain, retina, skeletal muscle, and heart muscle

What are the main target tissues for chronic Toxoplasma gondii infection?

Asymptomatic or mild flu-like illness

What is the most common manifestation of toxoplasmosis in immunocompetent individuals?

Toxoplasmic encephalitis

What is the most common manifestation of toxoplasmosis in immunocompromised patients?

horioretinitis, hydrocephalus, intracranial calcifications

What are the classic triad symptoms of congenital toxoplasmosis?

Pyrimethamine + Sulfadiazine + Leucovorin

What is the drug of choice for treating toxoplasmosis?

fat malabsorption

malabsorption associated with cystoisospora belli

D-xylose malabsorption

malabsorption associated with Cyclospora cayetanensis

Sarcocystis spp

What is the causative agent of sarcocystosis?

Sarcocystis hominis (from cattle) and Sarcocystis suihominis (from pigs).

What are the two species of Sarcocystis that infect humans as definitive hosts?

By consuming raw or undercooked infected meat containing sarcocysts (bradyzoites).

How do humans get infected with Sarcocystis hominis or Sarcocystis suihominis?

Intestinal sarcocystosis (diarrhea, nausea) and invasive sarcocystosis (myositis, fever).

What are the two forms of sarcocystosis?

The sporocyst, which is passed in feces of definitive hosts.

What is the infective stage of Sarcocystis for intermediate hosts?

Mild to severe diarrhea, nausea, vomiting, abdominal pain, and tachycardia (lasts ~36 hrs).

What are the symptoms of intestinal sarcocystosis?

Myositis, fever, eosinophilia, lymphadenopathy, subcutaneous nodules, and chronic pain.

What are the symptoms of invasive sarcocystosis?

No specific treatment, but albendazole, metronidazole, or corticosteroids may be used.

What are the recommended treatments for Sarcocystis infections?

• prolonged diarrhea

• fat malabsorption

• dissemination to other organs

severe infection of Cystoisospora belli

Eosinophilia and Charcot-Leyden crystals

this may be seen in the stool of Cytoisospora belli infection

1. Direct fecal smear

2. Concentration techniques

3. Acid fast staining

4. phenol-auramine staining

5. Iodine staining

Diagnosis for the visualization of oocyst in fecal specimen of Cystoisospora belli

1. Visualization of oocyst in fecal specimen

2. Entero-test

3. Duodenal aspirate

Diagnosis for Cystoisospora belli:

Alternating bouts of diarrhea and constipation

Symptom for Cyclospora cayetanensis

7 to 12 days

how may days does Cyclospora cayetanensis complete sporulation in a warm environment?

8 to 12 merozoites

In C. cayetanensis, 1st gen schizonts contains how many merozoites?

4 merozoites

In C. cayetanensis, 2nd gen schizonts contains how many merozoites?

Sporulated oocyst

Infective stage when consuming contaminated food or water

Bradyzoites

Infective stage when eating undercooked meat

Tachyzoites

Infective stage when doing blood transfusion

Tachyzoites

Infective stage of transplacental infection

Tachyzoites and Bradyzoites

Infective stage when doing organ transplantation

• Encephalomyelitis

• Myocarditis

• hepatitis

• retinochorditis

Symptom for chronic infection of Toxoplasma gondii

• fatigue

• Lymphadenitis

• fever

• chills

Symptom for acute infection of Toxoplasma gondii

Sabin Feldman Dye test

most sensitive and specific serologic test for Toxoplasma gondii

Miescher’s granules

Sarocystis spp. was initially referred as?

S. hominis

Microscopic in muscle of catte

S. suihominis

Macroscopic in muscle of pigs

intestinal form

from ingestion of Sarcocyst with bradyzoites

Muscular/invasive form

from ingestion of oocyst or sporocyst, rare and may involve a wide variety of tissues