TOPIC 5: Other Protozoans (Coccidians)

1. Cystoisospora belli

2. Cyclospora cayetanensis

3. Cryptosporidium (parvum and hominis)

4. Toxoplasma gondii

5. Sarcocystis (hominis and suihominis)

COCCIDIANS:

Phylum Apicomplexa

What phylum do coccidians belong to?

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

What type of protozoans are coccidians?

Gastrointestinal (GI) tract

What is the main site of infection for coccidians?

Coccidiosis

What disease is caused by coccidians infecting the GI tract?

They are usually asymptomatic in immunocompetent individuals.

How do coccidians affect immunocompetent individuals?

In immunocompromised hosts

In which type of host do coccidians become opportunistic pathogens?

It means they can cause severe infections when the immune system is weakened.

What does it mean for coccidians to be "opportunistic" in immunocompromised hosts?

1. Gametogony

2. Sporogony

3. Schizogony

What are the three main stages in the life cycle of coccidians?

The development of male (microgametes) and female (macrogametes)

What occurs during gametogony in the coccidian life cycle?

Microgametes

What type of gamete is developed for males during gametogony?

Macrogametes

What type of gamete is developed for females during gametogony?

The production of oocysts

What is the purpose of the sexual cycle (sporogony) in the coccidian life cycle?

Sporogony

What is the sexual reproductive cycle of coccidians called?

Schizogony

What is the asexual reproductive cycle of coccidians called?

The production of merozoites

What occurs during the asexual cycle (schizogony) in the coccidian life cycle?

Gametogony

Which stage of the coccidian life cycle is responsible for the development of male (micro) and female (macro) gametes?

Sporogony (Sexual Cycle)

Which stage of the coccidian life cycle is responsible for the formation of infectious oocysts?

Schizogony (Asexual Cycle)

In which stage do merozoites multiply within the host?

It allows the formation of male (micro) and female (macro) gametes, which fuse to form a zygote before developing into an oocyst

What is the significance of gametogony in the coccidian life cycle?

Unsporulated oocyst.

What is the diagnostic stage of coccidians?

Sporulated oocyst

What is the infective stage of coccidians?

The sporozoites are released and invade host cells

What happens to the zygote after gametogony?

Schizont formation

What stage follows the invasion of host cells by sporozoites?

To infect a new host when ingested

What is the function of a sporulated oocyst?

An unsporulated oocyst is immature and non-infectious, while a sporulated oocyst contains sporozoites and is infectious

What is the difference between an unsporulated and a sporulated oocyst?

Merozoites are produced through asexual reproduction

What happens inside the schizont?

They infect new host cells and continue the cycle by forming more schizonts or entering gametogony

What is the function of merozoites in the coccidian life cycle?

• Gametogony → Host’s GI Tract

• Sporogony → Environment

• Schizogony → Host’s GI Tract

Where does each stage of the life cycle occur?

In the host’s GI tract

Where does gametogony occur in the host?

In the environment.

Where does sporogony take place?

In the host’s GI tract.

Where does schizogony occur in the host?

It undergoes sporogony, developing into a sporulated oocyst

What happens to the unsporulated oocyst in the environment?

4 sporocysts, each containing 2 sporozoites

What does the sporulated oocyst contain?

By ingesting a sporulated oocyst from contaminated food, water, or surfaces

How does the host get infected?

• Good sanitary practices

• Adequate water treatment (boiling water)

• Proper washing of fruits and vegetables

What are the key methods for preventing and controlling coccidian infections?

Boiling water kills the infective oocysts, preventing transmission.

Why is boiling water recommended for water treatment in coccidian prevention?

No, chlorination is NOT effective against coccidian oocysts.

Is chlorination effective in killing coccidian oocysts?

Immature (unsporulated) oocyst

What is the diagnostic stage of Cystoisospora belli?

Mature (sporulated) oocyst

What is the infective stage of Cystoisospora belli?

Tropical countries with poor sanitary conditions

In what type of environment is Cystoisospora belli most commonly found?

Day care centers and mental institutions

Where are common places where Cystoisospora belli infections can occur?

Severe diarrhea

What symptom is commonly associated with Cystoisospora belli infection, particularly in infants?

Humans

What is the only known host for Cystoisospora belli?

Ingestion of sporulated (mature) oocysts

How is Cystoisospora belli transmitted?

2 sporocysts, each containing 4 sporozoites

How many sporocysts and sporozoites are present in a mature oocyst of Cystoisospora belli?

8 sporozoites

How many sporozoites does Cystoisospora belli have in total?

Distal duodenum and proximal ileum

Where does Cystoisospora belli primarily inhabit (habitat) within the human gastrointestinal tract?

They differentiate into microgametes and macrogametes, which eventually form zygotes.

How do merozoites contribute to the sexual cycle of Cystoisospora belli?

The oocyst lyses, releasing sporozoites.

What happens when the oocyst reaches the stomach?

The sporozoites infect the intestinal cells, particularly in the distal duodenum and proximal ileum.

Where do the sporozoites infect the host?

No, it is generally asymptomatic in immunocompetent individuals.

Is Cystoisospora belli infection always symptomatic?

Cystoisosporiasis

What disease is caused by Cystoisospora belli?

• Fever

• anorexia

• diarrhea

• vomiting

• body malaise

• weight loss

What are common symptoms of cystoisosporiasis?

• Prolonged diarrhea

• fat malabsorption

• potential dissemination to other organs.

What are complications of severe Cystoisospora belli infections?

fat malabsorption

What specific type of malabsorption is associated with severe Cystoisospora belli infection?

1. DFS (Direct Fecal Smear) / concentration techniques

2. acid-fast staining

3. phenol-auramine staining

4. iodine staining.

What laboratory techniques are used to diagnose Cystoisospora belli?

Eosinophilia and Charcot-Leyden crystals.

What additional findings may be seen in the stool of infected individuals?

Charcot-Leyden crystals

What characteristic crystals may be seen in the stools of individuals infected with Cystoisospora belli?

Entero-test (String Capsule) and Duodenal Aspirate.

What alternative tests can be used to detect Cystoisospora belli?

They appear as translucent, oval structures measuring 20-33 µm x 10-19 µm.

How do Cystoisospora belli oocysts appear under a microscope, and what are their typical dimensions?

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

What is the first-line treatment for Cystoisospora belli infection?

Pyrimethamine and sulfadiazine for 7 weeks.

What is an alternative treatment option for Cystoisospora belli?

• Nepal

• Peru

• Haiti

• United States

In which countries is Cyclospora cayetanensis commonly found?

Children

Which population group is commonly affected by Cyclospora cayetanensis in Peru?

Homosexual males

Which population group is commonly affected by Cyclospora cayetanensis in Haiti?

Raspberries, lettuce, and basil pesto salad.

What are some food sources associated with Cyclospora cayetanensis outbreaks?

It was originally called a Cyanobacterium-like body (CLB).

What was Cyclospora cayetanensis originally called?

Cyclospora cayetanensis

It was originally called a Cyanobacterium-like body (CLB).

4 sporozoites

What is the total number of sporozoites in a sporulated Cyclospora cayetanensis oocyst?

By ingestion of a sporulated (mature) oocyst.

How is Cyclospora cayetanensis transmitted?

• 2 sporocysts, each with 2 sporozoites, making a total of 4 sporozoites.

How many sporocysts and sporozoites are present in a sporulated oocyst? (Cyclospora cayetanensis)

Jejunum

Where does Cyclospora cayetanensis reside in the human body?

Two cycles.

How many cycles of schizogony occur in the host’s GI tract?

8–12 merozoites

How many merozoites are produced in the first generation of schizogony?

4 merozoites

How many merozoites are produced in the second generation of schizogony?

Cyclosporiasis

What disease is caused by Cyclospora cayetanensis?

Yes, it is generally self-limiting.

Is Cyclosporiasis self-limiting?

• chronic,

• intermittent alternating bouts of diarrhea and constipation,

• malaise,

• low-grade fever,

• fatigue,

• anorexia,

• weight loss,

• nausea, and

• vomiting.

What are the symptoms of Cyclosporiasis?

D-xylose malabsorption

What is a specific malabsorption issue associated with Cyclosporiasis?

Diagnosis is made through visualization of oocysts in fecal specimens using:

• direct fecal smear (DFS) / concentration techniques

• acid-fast staining.

How can Cyclospora cayetanensis be diagnosed?

Polymerase Chain Reaction (PCR).

What molecular technique can differentiate Cyclospora from Eimeria spp.?

Fluorescent microscopy

What microscopy technique is used to detect Cyclospora oocysts?

They appear as blue or green autofluorescent circles.

How do Cyclospora oocysts appear under fluorescent microscopy?

No, it is self-limiting, and treatment may not always be necessary.

Is treatment always necessary for Cyclosporiasis?

Trimethoprim-sulfamethoxazole (160/800 mg) twice daily for 7 days.

What is the first-line treatment for severe cases of Cyclosporiasis?

1. Cryptosporidium parvum

2. Cryptosporidium hominis

What are the two main species of Cryptosporidium?

Water contaminated with calf feces.

What is a common source of Cryptosporidium outbreaks?

Person-to-person transmission.

What is the most common mode of Cryptosporidium transmission?

Yes, nosocomial infections have been reported.

Can Cryptosporidium cause hospital-acquired infections?

Cryptosporidium parvum.

Which Cryptosporidium species from calves can infect veterinary attendants and visitors in dairy farms and zoos?

Cryptosporidium parvum.

Which Cryptosporidium species infects both humans and calves?

Cryptosporidium hominis.

Which Cryptosporidium species mainly infects humans?

By ingestion of thick-walled oocysts.

How is Cryptosporidium spp. transmitted?

Yes, they are already infective.

When Cryptosporidium oocysts are passed out, are they immediately infectious?

Four sporozoites.

How many sporozoites does each Cryptosporidium oocyst contain?

No, it does not contain a sporocyst.

Does Cryptosporidium oocyst contain a sporocyst?

Thick-walled oocysts and thin-walled oocysts.

What are the two types of Cryptosporidium oocysts?

They are passed out in feces and serve as the infective form for new hosts.

What is the function of thick-walled oocysts?

They remain inside the intestine and cause autoinfection, contributing to chronic infection.

What is the function of thin-walled oocysts?