MICR5830 L3: Human Gut Coccidia and Toxoplasma Gondii 3/5/25

What are the Coccidia?

-Isospora

-Toxoplasma

-Cyclospora

-Cryptosporidium (not the same tree clade)

What is the general gut Coccidia life cycle?

-Oocysts ingested

-Asexual reproduction (schizogony)

What happens during the gut Coccidia life cycle after oocysts are ingested?

Asexual reproduction (schizogony)

What happens during the gut Coccidia life cycle after Asexual reproduction (schizogony)?

Either repeated schizogony (asexual) or gametogony (sexual reproduction)

What happens during the gut Coccidia life cycle after gametogonysexual reproduction?

Resistant oocysts shed in feces

What happens during the gut Coccidia life cycle after resistant oocysts are shed in feces?

-Oocyst maturation

-Sporulation, sporogony

Where does oocyst maturation, sporulation and sporogony occur during the gut Coccidia life cycle?

Outside of the body (normally)

What human Coccidia oocyst is this?

-2 sporocysts

-8 sporozoites

Isospora (Cytoisospora) Toxoplasma

What human Coccidia oocyst is this?

-2 sporocysts

-4 sporozoites

Cyclospora

What human Coccidia oocyst is this?

-1 sporocyst

-4 sporozoites

Cryptosporidium; Sarcocystis

What structures would you expect to find in a mature coccidian oocyst after sexual reproduction?

-Residual body

-Sporocyst containing sporozoites

What is this?

-Self-limited watery diarrhea

-Worldwide distribution

-0.1-1.8% in immunocompetent stool, 2-20% in AIDS diarrhea

Human isosporiasis

What is this?

-Human isosporiasis

-Self-limited watery diarrhea

-Worldwide distribution

-0.1-1.8% in immunocompetent stool, 2-20% in AIDS diarrhea

What symptom does Human isosporiasis cause?

Self-limited watery diarrhea

True or False: Human isosporiasis only occurs to immunocompromised individuals (such as AIDS patients)

False, it is found in 0.1-1.8% of stool in immunocompetent people

What is this?

-Causes isosporiasis, diarrhea in AIDS

-Direct life cycle, faecal oral route

-Infects SI epithelium

Isospora belli (Cystoisopora belli)

What is this?

-Isospora belli (Cystoisopora belli)

-Causes isosporiasis, diarrhea in AIDS

-Direct life cycle, faecal oral route

-Infects SI epithelium

What epithelial cells does Isospora belli/Cystoisopora belli infect?

Small Intestine

How many sporocysts does a mature Isospora/Cystoisopora belli oocyst have?

How many sporozoites each?

-2 sporocysts

-4 sporozoites each

What is this?

-Mature Oocyst: 2 sporocysts with 4 sporozoites each during infective stage

Isospora belli (Cystoisopora belli)

How does Isopora/Cystoisopora belli reproduce and give rise to merozoites?

-Schizogony

-Asexual reproduction

What happens to the Isopora/Cystoisopora belli merozoites created from schizogony?

1) Invade new cells, continue schizogony

2) Develop male/female gametocytes, fuse to form oocysts excreted in stool

Where is Isospora/Cystoisopora belli acquired?

Contaminated food and drink

What symptom does Isospora/Cryptospora belli cause in HIV/AIDS patients and returning travellers?

Diarrhea

Where does Isospora/Cryptospora belli predominantly cause diarrhea in AIDS patients?

Low-income countries

True or False: Isospora/Cryptospora belli causes diarrhea in AIDS patients at a more significant rate than Cryptosporidium and microsporidia

False, Cryptosporidium (14%) and Microsporidia (12%) are more significant than Isospora (2.5%)

True or False: Isospora cysts are small

False, they can produce large 30um oocysts

How is Cystoisospora, Cyclospora and Microsporidia diagnosed?

Multiplex PCR assay

What microscope/stain would you use to diagnose Isospora/Cryptospora belli?

-Phase contrast

-Wet film, iodine

-Ziehl-Neelsen acid-fast stain

True or False: Isospora/Cryptoisospora belli is not included in commercial molecular diagnostic panels for enteric pathogens

True, this is why some cases are missed

How is Isospora/Cryptoisospora belli treated?

-Trimethoprim

-Sulfamethoxazole

-10 day course

What is this?

-Trimethoprim

-Sulfamethoxazole

Cotrimoxazole

What do Cotrimoxazole (Trimethoprim-sulfamethoxazole) inhibit while treating Isospora/Cryptoisospora belli?

-Tetrahydrofolate synthesis

-DNA synthesis

What type of drug is Sulfamethoxazole?

Sulfonamide

What does Sulfamethoxazole inhibit?

Folic acid synthesis

Where do we normally get folic acid from?

Diet

What does Trimethoprim inhibit?

Dihydrofolate reductase enzyme

Why would it be beneficial to use Trimethoprim to inhibit dihydrofolate reductase?

Parasite enzymes are inhibited at lower concentrations

True or False: Parasite enzymes are more active at mammalian concentrations than lower ones

True

True or False: Maintenance treatment is necessary to prevent relapses in AIDS patients receiving Cotrimoxazole for Isospora

True

What is this?

-Self-limiting diarrhea from intestinal epithelia infection

-One of most common water borne disease

-Severe/fatal in immunocompromised

Cryptosporidiosis

What is this?

-Cryptosporidiosis

-Self-limiting diarrhea from intestinal epithelia infection

-One of most common water borne disease

-Severe/fatal in immunocompromised

What symptom does Cryptosporidiosis cause?

Self-limiting diarrhea

What epithelia does Cryptosporidium infect?

Intestinal epithelial tissue

Which infection is one of the most common waterborne disease?

Cryptosporidiosis

What region of the USA was infected by a huge amount of Cryptosporidiosis cases?

Milwaukee

True or False: Self-limiting caused by Cryptosporidiosis is often severe/fatal in immunocompromised individuals

True

What is the dominant species of Cryptosporidium in humans?

Cryptosporidium parvum

What are some other species that cause Cryptosporidiosis in humans?

-C. hominis

-C. canis

-C. felis

-C. meleagridis

-C. muris

True or False: Cryptosporidium only affects immunosuppressed people

False, it can cause symptomatic illness in immunocompetent people

What are the two major species of Cryptosporidium in humans?

-C. parvum

-C. hominis

What is this?

-C. parvum

-Dominant Cryptosporidium species in humans

-Infects cattle, sheep, goats (livestock)

What is this?

-C. hominis

-Second most common Cryptosporidium species in humans

-Infects mammals

What does C. parvum infect?

-Livestock, humans

-Cattle, sheep, goats

What does C. hominis infect?

Humans, mammals

What Cryptosporidium species are dominant in Europe?

-C. parvum

-C. hominis

What Cryptosporidium species are dominant in the Middle East?

C. parvum

What Cryptosporidium species are dominant in Australia?

C. hominis

What Cryptosporidium species are dominant in the rest of the world?

C. hominis (usually)

Where is the infection rate with Cryptosporidiosis highest?

Mexico

During what life stage would you expect Cryptosporidiosis oocysts to be thick-walled?

-Survival

-Transmission

During what life stage would you expect Cryptosporidiosis oocysts to be thin-walled?

Autoinfection

What life stages does Cryptosporidiosis have in humans?

-Oocysts

-Sporozoites

-Trophozoites

-Merozoites

-Male/female gametes

-Zygote

Where do Cryptosporidiosis asexual/sexual reproduction occur in humans?

Intestines

What is the first step of the Cryptosporidiosis life cycle?

-Thick-walled oocysts are excreted

-Feces, respiratory droplets

What happens in the Cryptosporidiosis life cycle after the thick-walled oocysts are excreted in feces?

Ingestion/inhalation of oocysts

What happens in the Cryptosporidiosis life cycle after oocysts are ingested/inhaled?

-Excystation (intestines/lungs)

-Releases sporozoites

What happens in the Cryptosporidiosis life cycle after excystation releases sporozoites in the intestines/lungs?

-Sporozoites parasitize intestinal cells

-Trophozoites develop

What happens in the Cryptosporidiosis life cycle after sporozoites develop into trophozoites in the intestinal cells?

-Asexual reproduction in intestine

-Merozoites produced

What happens in the Cryptosporidiosis life cycle after merozoites are produced asexually in the intestine?

Merozoites form male/female gametes

What happens in the Cryptosporidiosis life cycle after merozoites form male/female gametes?

-Sexual fusion

-Zygote is produced

What happens in the Cryptosporidiosis life cycle after sexual fusion forms a zygote?

-Zygote germinates

-Thick-walled and thin-walled oocysts are formed

True or False: After sexual fusion, the zygotes that germinate are only thick-walled oocysts

False, they become both thick-walled and thin-walled oocysts

What is an unusual location of Cryptosporidium?

Intracellular, extra-cytoplasmic coccidian found in small intestine

What are the clinical features of Cryptosporidiosis?

-Asymptomatic

-Watery diarrhea

-Infected lungs, digestive tract organs

What is this?

-Watery diarrhea within 7 days

-Dehydration, weight loss, abdominal pain, fever, nausea, vomit

Cryptosporidiosis

What is this?

-Cryptosporidiosis symptoms

-Watery diarrhea within 7 days

-Dehydration, weight loss, abdominal pain, fever, nausea, vomit

True or False: Cryptosporidiosis symptoms such as watery diarrhea, dehydration, abdominal pain, fever, nausea and vomit are usually short lived (1-2 weeks)

True

True or False: Cryptosporidium have been found in the lungs and digestive tract

True

How is Cryptosporidiosis transmitted?

-Fecal-oral route

-Contaminated water, food

What are some sources of Cryptosporidiosis transmission?

-Waterparks

-Community swimming pools

-Daycare centers

How is Cryptosporidiosis transmitted zoonotically?

-Exposure to infected animals

-Exposure to their poop

True or False: Immunity to Cryptosporidiosis is incomplete and children in endemic areas can frequently have multiple episodes

True

True or False: C. hominis infection provides partial protection against C. parvum

True but heavy on "only partial"

What are some conditions caused by Cryptosporidiosis spreading from the intestine to the hepatobiliary/pancreatic ducts?

-Cholangiohepatitis

-Cholecystitis

-Choledochitis

-Pancreatitis

What could cause these following conditions associated with Cryptosporidiosis?

-Cholangiohepatitis

-Cholecystitis

-Choledochitis

-Pancreatitis

Intestine -> hepatobiliary and pancreatic ducts spread

What are the major morbidity causes of children in developing countries?

1) Rotavirus

2) Cryptosporidium

3) Enterotoxigenic E. coli

4) Shigella

What is the 1st highest child killer in developing countries?

Rotavirus

What is the 2nd highest child killer in developing countries?

Cryptosporidium

What is the 3rd highest child killer in developing countries?

ETEC

What is the 4th highest child killer in developing countries?

Shigella

How is Cryptosporidiosis diagnosed?

-Light microscopy

-Direct FAT and immunochromatographic dipsticks

-PCR

What microscope/stain would you use to diagnose Cryptosporidiosis?

-Ziehl-Neelsen (acid-fast)

-Auramine

-Safranin

What are some microscopy techniques to diagnose Cryptosporidiosis oocysts and Giardia cysts?

-Ziehl-Neelsen (acid-fast)

-Heine negative stain

What are some Immunological assays to diagnose Cryptosporidiosis oocysts and Giardia cysts?

-IFA

-Direct (DFA)

-Indirect (IIF)

-Fluorescent-monoclonal-antibody detection

-ELISA

What are some Nucleic Acid-based techniques to diagnose Cryptosporidiosis oocysts and Giardia cysts?

-FISH

-PCR

-Quantitative PCR

-Droplet digital PCR

-LAMP

-Enteric stool PCR panel

What are some requirements for a Ziehl-Neelsen stain to work on Cryptosporidiosis?

-5.5 um

-Bright red

What is this?

-Excellent results, not recommended by CDC

-Used for staining Cryptosporidia oocysts

Safranin/Carbol Fuchsin

What species oocysts do Safranin/Carbol Fuchsin stains work best on?

Cyclospora

How many sporozoites would you expect to see in a Cryptosporidium parvum that has been stained using modified acid-fast technique?

4