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41 Cards in this Set
- Front
- Back
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What kind of a parasite is Giardia intestinalis?
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Intestinal protozoan parasite of vertebrates
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What does Giardia cause?
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Significant global cause of endemic and epidemic diarrhea
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Is Giardia usually fatal?
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No it isn't, but it is the most common enteropathogen in the world and it plays a role in the millions of deaths occuring annualy because of diarrheal illness
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Where is Giardia a problem?
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Developing countries: ~1/3 of the population in these countries have had it
Most commmonly diagnosed parasite infection in North America Worldwide prevalence of acute infection: 20-30% |
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When can Giardia be fatal?
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If it infects immunocompromised ppl
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How long did it take to confirm that there was a relationship btw cause and effect of Giardia and diarrhea? Why?
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50 years
Very difficult to establish cause and effect --> Need to isolate a person who has been infected by pure parasite... |
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What kind of a parasite is giardia?
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flagellated
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Where does the parasite stay in the host?
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Upper part of the small intestine
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What kind of a life cycle does the parasite have?
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Direct life cycle
Doesn't depend on an intermediate host --> Doesn't go from animals --> humans |
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Is this a zoonotic parasite?
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No, doesn't really infect animals, just mainly humans
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What is the infective stage of the parasite?
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Cyst
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How many cysts are required to infect a human?
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~10 cysts (not a lot, but still more than entamoeba histolytica)
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Describe the Giardia cysts
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Resistant to chlorine
Viable for several months in surface water Can survive in water at 4 C for at least 3 months NOT resistant to freezing Dimensions: 6-10 um Elliptically shapped |
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What is the cyst wall made of?
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Fibrous components containing galactosamine and ptns
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What induces the excystation process?
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Stomach acid
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What are the biological features of giardia?
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2 nuclei (NO nucleoli)
Absence of fctnal mitochondria Lack peroxisome Altered Golgi apparatus Dependent on anaerobic respiration |
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What happens after a person ingests a giardia cyst?
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2 trophozoites emerge in the duodenum and attache to the host's small intestinal mucosa
They multiply by binary fission in the lumen of the intestine They colonize the bowel Some of the trophozoites encyst and are released with the fecal material |
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How many pairs of flagella does the Giardia trophozoite have?
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4
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Where are the flagella?
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They originate from the basal bodies located near the nucleus
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What kind of a body does the Giardia trophozoite have?
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Median body (unique)
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What can be found in the cytoplasm of the Giardia trophozoite?
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Virus and bacteria
-->These are endosymbionts, they're neutral, don't really do anything |
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What is the ventral disk of the parasite (in the trophozoite stage)?
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Complex of microtubules and fibrous structures
Serves as organelles of attachment -->Structure is rich in tubulin, termed Giardin |
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Is Giardia an invasive parasite?
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Not really, compared to entamoeba
Giardia generally just attaches instead of invading |
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How many species of Giardia infect humans?
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Just one:
G. duodenalis/lamblia/intestinalis |
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Why is it difficult to study this parasite?
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Different species of giardia infect different animals
Can't just extrapolate the effects of one species in mice to humans |
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How can Giardia be transmitted?
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1) Contaminated drinking water
2) Contaminated rivers, lakes (Beaver fever) 3) Ingesting contaminated food 4) Person-person contact |
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Can Giardia lamblia/intestinalis infect animals?
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Yes, can infect other mammals, which it uses as a reservoir
-->Important in transmission |
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What are the clinical symptoms of Giardia?
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Most ppl (90%) are asymptomatic
Symptoms tend to appear 6-15 days after infection and can last for 2-6 weeks Loss of weight and appetite Malabsorption and Dehydration Explosive diarrhea (unlike in Entamoeba) |
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Describe the pathology of giardiasis
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Can be asymptomatic or cause severe enteropathy
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How can pathology in the small bowel be evaluated?
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Measuring the villus : crypt ratio
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What happens to this ratio during the acute phase of infection?
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Decrease of the height of villi
Increase in the height of the crypt |
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What are the different types of pathology that giardia can cause?
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Acute
Self-limitiing Chronic |
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What is characteristic of giardia pathology?
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Malabsorption
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When does Malabsorption occur?
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During the acute phase of infection
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When is malabsorption eliminated?
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Disappears after elimination of the trophozoite from the intestine
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What are the 3 distinct phases of the life cycle?
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Latent period
Acute phase:~6 days after, expansion of trophozoites Elimination phase |
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How do you treat giardia?
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Same an entamoeba
-Metronidazole -Tinidazole -Ornidazole -Quinacrine |
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What does metronidazole do?
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Binds and damages DNA
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What type of DNA does Metronidazole?
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Binds DNA in anaerobic protozoa
-->Giardia, ameba, trichmonas vaginalis, Also highly active vs anaerobic G- bacteria Also inhibits aldehyde dehydrogenase, which breaks down alcohol |
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What are the CDC guidelines to prevent and control giardia infection?
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Good hygiene
Avoid contaminated water Avoid eating food that may be contaminated Prevent contact and contamination with feces during sex |
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What kind of organism is Giardia?
What kind of organelles does it have? |
Eukaryotic
Has: nuclei, ribosomes, lysosomal vacuole, multiple linear chromosomes |
