Giardiasis Flashcards
what type of parasite is Giardia?
intestinal commensal
flagellate protozoa in upper GI tract
monoxenous (species specific)
which species is Giardia commonly found?
vertebrates such as humans, companion animals, livestock, wild animals
worldwide
what is the feeding stage of Giardia and how does it divide?
Trophozoite divides by binary fission
describe the trophozoite stage of Giardia
bilaterally symmetric
Pyriform (tear drop) shape
two nuclei
describe the cyst stage of Giardia
thick walled
4 nuclei
trophozoites release from cysts
how many trophozoites release from cysts?
two
ID the Giardia stage
trophozoite
ID the Giardia stage
cyst
what causes Giardia?
G. duodenalis aka G. lamblia/intestinalis/enterica
what does this diagram demonstrate?
the genetic assemblages of Giardia duodenalis
what species make up genetic assemblage A & B?
wide range of domestic and wild animals (include humans)
Sub AI = domestic livestock and pets
Sub AII = humans
what species make up genetic assemblage C & D?
dogs and wild canids
NEVER found in humans
what species make up genetic assemblage E?
hoofed stock
such as cattle, sheep, goats, pigs, horses
what species make up genetic assemblage F?
cats
what species make up genetic assemblage G?
rodents
what species make up genetic assemblage H?
seals
list the modes of transmission of Giardia?
direct fecal ingestion of cysts
indirect ingestion of contaminated water, food, transport hosts, infected prey
re-infection from animal fur when they groom
what’s the prepatent period of Giardia in dogs?
4-12 days
average 8 days
what’s the prepatent period of Giardia in cats?
5-16 days
average 10 days
describe the importance of virulence-specific surface protein (VSP)?
cysteine rich surface protein
covers entire giardial trophozoite cell
main factor responsible for immune evasion
where are Giardia trophozoites most commonly found in dogs?
duodenum to ileum
where are Giardia trophozoites most commonly found in cats?
jejunum and ileum
where are Giardia cysts found in dogs/cats?
duodenum, releases two trophozoites
describe the proposed mechanism of Giardia
- trophozoites bind to GI tract
- apoptosis of enterocytes
- loss of epithelial barrier function
- hypersecrete Cl-
- diffuse microvillus shortening
- immune reaction
- inhibit brush border enzymes and trypsin
- interference with bile salt metabolism
describe the symptoms of Giardia
often asymptomatic (shed cysts in feces)
self-limiting illness in immunocompromised
who is Giardia most common in?
young animals
illness is more severe and persistent
how would the feces of a dog/cat look if they likely had Giardia?
greasy stool
light colored, mucoid, malodorous (smells bad)
may or may not be D
what is the main Giardia species in birds?
G. psittaci
which birds most commonly get G. psittaci?
parrots, specifically budgerigars and cockatiels
they also have increased mortality for an unknown reason
what’s the zoonotic potential for G. duodenalis?
very few direct animal to human cases
beavers most common for zoonotic transmission in USA
how would you cliinically diagnose Giardia?
clinical suspicion (history at farm/home, D unresponsive to other treatments)
microscopic exam of fresh feces
fecal immunoassays
fecal PCR
