Giardia Flashcards
How is Giardia an unusual eukaryote?
has 2 nuclei
What are the scientific names for Giardia?
Giardia lamblia, Giardia duodenalis, Giardia intestinalis
How does Giardia take part in millions of deaths world wide, especially in developing countries?
causes endemic and epidemic diarrhea. diarrheal illness leads to secondary infections
Where does Giardia reside in the body?
upper part of the small intestine
What is the intermediate host?
does not have one. it has a direct life cycle
Which stage is the infective stage?
the cyst. can survive in frozen-over waters for 3 months
How many cysts are sufficient to infect humans?
10
Describe how the infection progresses
- ingest cyst
- excysts in the small intestine mucosa and 2 trophozoites emerge
- binary fission in lumen of intestine & colonize small bowel
- some trophozoites encyst & are released in feces
Describe the morphology of the parasite
- 4 pairs of flagella from basal bodies near the nucleus
- have median bodies
- endosymbiotic viruses & bacteria in cytoplasm
What makes Giardia classified as a eukaryote?
has nuclei, ribosomes, lysosomal vacuoles, mult. linear chromosomes
+ flagella
What makes Giardia unusual?
- 2 nuclei
- NO functional mitochondria
- altered golgi apparatus
- ventral disk
- median body
What is the ventral disk?
is an organelle of attachment.
made of microtubules & fibrous structures
structure is rich in tubulin & giardin
How can Giardia be transmitted?
through contaminated water and food, and person-person contact
What are the 3 phases in its life cycle?
latent period
acute phase
elimination phase
What are some features of the cyst?
- resistant to chlorine
- elliptically shaped
- cyst wall is composed of polymers of galactosamine + proteins
What did Giardia nomenclature used to be based on?
on the animal host species from which it was obtained
not useful because Giardia is ubiquitous and does not have host specificity
How is Giardia named now?
based on morphological features of the median body
What are the 3 groups of Giardia?
the amphibian group (long body)
the human group (claw body)
the rodent/bird group (round body)
Name a species in the amphibian group
Giardia agilis
Name a species in the human group
Giardia lamblia/duodenalis/intestinalis
Name species in the rodent/bird group
Giardia muris, Giardia ardae, Giardia microti
What is DNA hybridization?
a molecular technique that measures the degree of genetic similarity between species so that they can be placed in a phylogenetic tree
What are the advantages of DNA hybridization over protein electrophoresis?
- both expressed & non-expressed genome sequences can be examined
- genomic DNA is less susceptible to environmental influences
What does genetic variability make difficult to predict?
transmission, pathogenicity, characteristics of isolates from one endemic area to another
What are the advantages of using PCR?
- sensitivity allows the detection of infectious agents in environmental samples
- allow to distinguish between human and animal parasite species
What has some evidence suggested about areas where Giardia transmission is less intense between humans?
zoonotic transmission is more likely to occur
What is Thompson’s classification?
4 main cycles in which host-specificity & zoonotic assemblages can be maintained in nature.
- assemblages A & B maintained by direct transmission b/w humans
- assemblage E b/w livestock
- assemblage C/D b/t dogs
- assemblage F b/w cats
assemblage A (more so than B)can also infect animals
What are the symptoms of Giardia?
asymptomatic OR enteropathy with malabsorption
can be acute or chronic, reasons not known
How effective are the Giardia medications?
most are 90% effective but now there is resistance to them
How does the innate immune system protect us against Giardia?
mucus in small intestine acts as a barrier, human milk can kill Giardia trophozoites
How does the adaptive immune system protect us against Giardia?
humoral & cell-mediated response cause a local inflammatory reaction, plasma cells produce IgA
What percentage of raw sewage waters and total water tested came out positive for Giardia?
73% raw sewage and 25%
numbers are expected to be higher because of low effectiveness of tests
What emerging technology can protect us against Giardia?
UV disinfection.
- environmentally friendly
- low cost
- becoming widely accepted in water treatment plants
