GI protozoa Flashcards
What causes amebiasis?
Entamoeba histolytica
What is the transmissible form of entamoeba histolytica?
Cyst form
What is the pathogenesis of entamoeba histolytica?
- Cyst form breaks out and invades wall of colon 2. Can remain in lumen to replicate or penetrate intestinal wall to go to brain, liver, etc
Which pathogen causes characteristic flask shaped lesions?
Entamoeba histolytica
Who is more infectious in an entamoeba histolytica infection - symptomatic or asymptomatic person?
Asymptomatic - more cysts in stool
What are the symptoms of symptomatic entamoeba histolytica infection?
Bloody, mucousy diarrhea (fever is rare)
What is the route of transmission for entamoeba histolytica?
Fecal-oral, ingestion of cysts
What are the properties of invasive amebiasis?
- Penetration of intestinal wall by trophozoites 2. Flask shaped lesion 3. Spread via blood stream - liver abscess, abdominal pain, fever, increased WC
In amebiasis infection, solid stool contains more cysts or trophozoites?
Cysts
What is the cause of giardiasis?
Giardia lamblia
What is the infective stage in giardia lamblia?
Cyst
What is the lifecycle of giardia lamblia?
- Excysts in duodenum 2. Multiples by longitudinal binary fission 3. Trophozoites on mucosa of duodenum 4. Trophozoites and cysts shed in stool 5. Trophozoites disintegrate, cysts reinfect
What are the stool characteristics for giardiasis infection?
- Greasy, foul smelling floating stools 2. No blood 3. No fever
What are the properties of symptomatic vs asymptomatic individuals with giardiasis infection?
- Symptomatic - frank abdominal distress, likely passing trophozoites in stool 2. Asymptomatic - tend to pass cyst form
What causes balantidiasis?
Balantidium coli
What are the properties of balantidium coli?
- Only ciliated organism that infects humans 2. Disease is very similar to entamoeba histolytica 3. Can stay in lumen or invade for dysentery like symptoms 4. Frequently associated with pigs
What is the life cycle for balantidium coli?
- Ingestion of infective cyst 2. Trophozoite remains in colon lumen to multiply, or invades wall of colon to multiply 3. Trophozoite detected in stool and shed
What causes cryptosporidiosis?
Cryptosporidium parvum
What is the transmission for cryptosporidium parvum?
Ingestion of fecal oocysts
What are the symptoms of intestinal cryptosporidiosis?
- Profuse watery diarrhea accompanied by cramping, fatigue, and weight loss. 2. No blood
What is the life cycle for cryptosporidium parvum?
- Ingest oocyte 2. Sporozoites attach to surface of intestinal epithelium and mature 3. Sexual forms develop and produce fertilized oocyst 4. Mature oocyst detected in stool 5. Cows are known reservoirs
What stain is used to detect mature oocysts in cryptosporidiosis?
Acid fast stain
What is unique about cryptosporidium parvum pathogenesis?
Sexual and asexual reproduction occur in host
What is the life cycle for isospora belli?
- Ingestion of immature oocyst with sporocyst 2. Sporozoites divide and mature in cells of intestinal mucosa 3. Sexual forms develop and produce fertilized oocyst
What are the properties of isospora belli?
- Often seen in immunocompromised patients 2. Fever, diarrhea, weight loss
What are the features of cyclospora?
- Profuse, watery diarrhea 2. Cramping, fatigue, weight loss 3. Prolonged symptoms (weeks) 4. Similar to cryptosporidiosis
What is the diagnosis for cyclospora?
Oocysts fluoresce under UV light
What causes microsporidiosis?
Microsporidia
What are the properties of microsporidia?
- Obligate intracellular parasites 2. Primitive eukaryotes 3. Infection via ingestion of spores 4. Intestinal disease or disseminated disease
What are the extraintestinal signs of microsporidiosis?
- Keratoconjunctivitis - early dissemination 2. Dependent on organ system involved
