2 + 3 - Helminth Intro Flashcards
What do each group of helminths have for identifying?
Basic features - size, reproductive, host and tissue specificity, transmission, pathogenesis, morphological features important for identification
Basic life cycles
Diagnosis (fecal based methods)
What are the basic features of nematodes?
Roundworms
They are parasitic and free-living species
Tiny (<1mm) to enormous (40cm)
Genders separate (dioecious), sexual repro within DH
Eggs, or larvated eggs, or larvae
Direct and indirect life stages
Live in many diff hosts/tissues w/ host/tissue specifity
Some larvae undergo complicated migrations
What is the strongylid nematode translation?
Egg with morula -> larvated egg -> moulting larva -> ensheathed 3rd stage infective larvar -> DH
What does oviparous mean?
female nematode that passes eggs in the single-cell stage or the morula stage (solid mass of cells,c lustered together)
What does ovoviviparous mean?
Female nematode that passes eggs with a first stage larva contained (and visible)
What does larviparous mean?
Female nematode that retains the eggs within the uterus till they mature and hatch and then pass live first-stage larvae
How does the transmission of nematodes work?
DH infected by ingestion of eggs or larvae from the enviro, contaminated food/water
ingestion of larvae within IH or PH -> skin penetration by larvae
inoculation of larvae from an arthropod vector
Prenatally from mom-fetus
thru mammary gland from mom to young
How are nematodes identified?
ID of nematode adults req details such as host, size of worm, morphological features of the worm, usually on head/tails
Egg morphology is more commonly used for diagnosis. Also varies for ex. the presence or absence of larvae in the egg, size, and any other morphological features (operculum, polar plugs, color, etc)
What is baermann larval sedimentation
fecal float
live larvae in fresh feces submerged in water wriggle out and sink
What are the basic features of cestodes?
Segmented flatworms
All species parasitic
some time (2mm) some enormous (12m)
hermaphrodite
all have an indirect life cycle with IH
adults in DH parasitize the GI system, cause few problems and prod eggs immediately infective for the IH
larval stages in tissues of IH may cause serious dz
Asex reprod may occur in IH depending on species
What is the structure of a cestode?
A tiny head called a rostellum (with hooks)
Next is the suckers (4)
^^ scolex includes rostellum + suckers
following is the next, and then the body or strobila
The farther up is immature segments, then mature and then gravid segments
Segments = proglottid
What are the basic features of trematodes
leaf-shaped flatworms
all parasitic
tiny <1mm to giant 10cm
hermaphroditic
sexual repro occurs in DH
all have an indirect life cycle with IH
first IH always has a gastropod (slug or snail)
Asexual repro in gastropod IH
adults in DH parasitize GIT or lungs; sometimes pathogenic
larval stages in IH parasitize many tissues; rarely pathogenic
What is a basic structure of a trematode?
has a mouth, oral sucker, acetabulum, pharynx and caeca
What are the trematode life cycle stages?
Egg with miracidium -> miracidium(IMPORTANT) -> sporocyst -> redia -> cercaria (IMPORTANT) -> metacercaria (MPORTANT) -> egg with morula
How are trematodes transmissable?
DH infected by ingestion of metacercariae on vegetation or in IH
Skin penetration by cercariae
thru the mammary gland from mother to suckling young
