Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

24 Cards in this Set

  • Front
  • Back
What is the epidemiology of Entamoeba histolytica
10% infected, but 90% asyptomatic. Fecal-oral route of transmission
What are the virulence factors of pathogenic invasive amoebae
1. Galactose adherence protein (attaches to intestinal epithelium)
2. Amoebapore (cell lysis)
3. Surface cysteine proteinases (activate complement, degrade fibronectin, collagen, basement membranes)
4. Phagocytic capacity
How does the host resist ameboid infection
Colonic mucus (glycoprotein) and IgA inhibit adherence of amoebae to epithelial cells. Normal flora of bacteria also provide competition
How do Entamoeba histolytica trophozoites invade the host
They must adhere in order to kill. They induce apoptosis and flash-like lesions. They contact, kill, and phagocytize WBCs. This results in impaired local host immune response and lessened initial local inflammation. They penetrate intestinal mucosa, spread via bloodstream to extraintestinal sites such as the liver
What are the characteristics of amebic ulcers in the intestine
Classic flask shape, trophozoites undermining mucosa, ulcers with small, raised, swolled edges and normal mucosa in between
What are the symptoms and pathology of Ameobic diseases
1. Most infections are asymptomatic
2. Invasive intestinal amebiasis: variable severity, from diarrhea to dysentery. This can range from frequent loose stools and ab cramps to acute colitis and profuse bloody diarrhea or dysentery, fever nausea and anorexia. An ameboma develops in only 1% of these patients
3. Extra-intestinal: trophozoites only, spread to bloodstream. Does not require history of intestinal amebiasis
How are Entamoeba histolytica trophozoites diagnosed
Found in liquid stools. ELISA. Sigmoidoscopic examination to find ulcers
What is the immune response to Entamoeba histolytica trophozoites
Lumen dwelling noninvasive elicit no apparent host response. sIgA against galactose adherence protein may protect against invasion. Recurrence of invasive amebiasis is rare
What is the epidemiology of Giardia lamblia
Worldwide distrubution. Fecal-oral route direct or waterborne
What is the pathogenesis of Giardia lamblia
Adherence of trophozoites to surface of upper small intestine. Damage to the the intestinal surface is usually mild. The villi are mechanically blunted, possibly leading to malabsorption syndrome. Great numbers can carpet the mucosa
What is the immune response to Giardia
T cells and macrophages are implicated in control of Giardia infection. Individuals may be repeatedly reinfected with Giardia, due to antigenic variation
What are the 4 different clinical symptoms of Giardia
1. Asymptomatic
2. Mild diarrhea
3. Explosive, watery, foul smelling diarrhea
4. Chronic diarrhea with steatorrhea
How is Giardia lamblia diagnosed
Cysts/trophozoites in the stool, though they may not always be present.
What is the treatment for Giardia lamblia
Metronidazole, albendazole, atabrine
What is the epidemiology of Cryptosporidium parvum
Zoonotic infection, infects many mammals
What is the epidemiology of Cryptosporidium hominis
Human-Human infection. Fecal oral or oral anal route. Infectious dose is very small. Oocysts are extremely resistant
What is the pathogenesis of Cryptosporidium sp.
Intracellular parasite, sequestered within enterocyte cytoplasm to area facing intestinal lumen. Lives in brush border of small intestine. Capable of internal autoinfection. Toxin not identified
What is the immune response to Cryptosporidium sp.
Immunocompromised, children, and the elderly are most susceptible. Cell-mediated immunity is the most important response. sIgA may protect against the initial infection
What are the clinical symptoms of Cryptosporidium sp.
In normal individuals, asymptomatic or profuse, watery diarrhea with cramps and low grade fever. Self limited, 1-2 weeks
In the immunocompromised, it presents with the same symptoms, but may be life-threatening
What is the treatment for Cryptosporidium spp.
Treat the diarrhea with rehydration. Nitazoxamide has been approved for 1-11 year children
What is the main point to remember with microsporidia
There is no known effective treatment
What is the main symptom to remember with Apicomplexa
Watery diarrhea. Caused by Cyclospora cayetanensis, Isospora belli, and Sarcosystis
What are the main mechanisms of immune evasion by intestinal protozoan parasites
Intraluminal location (shelters intestinal parasites from many immune effector mechanism)
Resistant parasite surfaces (cuticles, cysts, and capsules reduce sensitization and inhibit function of effector cells and molecules)
Intracellular location of Cryptosporidium, Cyclospora, Isospora, and Microsporidia
What is the most important immune response to opportunistic intestinal protozoan parasites
Cell-Mediated immunity