parasitology 2 Flashcards
helminth life cycle-route of infection
ingestion of infective stage
ingestion of paratenic/intermediate host
maternal (transplacental, transmammary)
skin penetration
arthropod-borne
generalities about helminths
macroparaites-do not multiple inside of definitive host: number of parasites the host is infected with is what they have
complex multicellular organs
often highly host specific in definitive host but not always
direct life cycle
fecal oral transmission
environmental oral
nematoda
thread
non-segmented, cylindrical, generally tapered at both ends
most successful of all worms
free living soil nematodes
major plant and animal parasite
range in size from micrometer to meter
general characterisitic
cuticle: body surface
cuticle is flexible not metabolically active
like arthropod exoskeleton
may form spines, ridges, secondary sexual structures
fluid filled body cavity
intestine and reproductive system are suspended in cavity
body wall has a muscle layer provides movement
lost of structures for sensing the environment
neurotransmitter in nematoda
acetylcholine
gamma-aminobutyric acid (GABA)
nematoda digestive system
food depends on species and location in host
oral opening: buccal capsule (Cavity)
esophagus (pharynx) intestine
reproductive system
general separate sexes
females usually bigger than males
males have secondary structures: spinules
females produce eggs or larvae
nematoda development
cuticle restricts growth
all nematodes go through 4 molts
stages between molts are L1, L2, L3, L4, and adult
L3 rule
nematode stage infective for definitive host is almost always L3
strongylida porphology
bursate nematodes: bursa used in reproduction holds female
macroscopic to 10cm
slender
most of the important species in the GI tract
depending on species, larva or adult may be most pathogenic stage
strongylida pathogenic mechanisms
varies with species
damage from tissue-phase of development
blood or tissue feeding
inflammation/immune response-affected GI function
anorexia-multifactorial
strongylid eggs
direct life cycle
oval, thin shelled contain a morula (blastomeres) cant be differentiated
diagnosis: fecal flotation
strongylida life cycle (Except metastrongyloidea)
egg voided in feces
L1 hatch and develop to L3 ( 2 molts)
L3 retains cuticle of L2 as protective sheath (ensheathed L3)
L3 ingested by host (infective stage)
larvae travel to predilection site and develop to adults
eggs and larvae dont like
temperature extremes
freezing and thawing cycles
desiccation
tropisms
hydro +
thermo +
geo -
photo +
hypobiosis
arrested or inhibited development until conditions are ideal
L3 hypobiosis
trichostrongylus, ancylostoma, cyanostominae
L4 hypobiosis
osteragia, teladorsagia, haemonchus
stimulus for arrested develelopment
environmental
host immnunity
superfamily trichostrongyloidea
L3 develop and survive in weeks to months depending on weather
pasture parasites: generally don’t do well in housing or on dirt
minimum prepatent period: usually 3-4 weeks depending on species
hypobiosis common-affect epidemiology and control
adult life span-month
all grazing ruminants have trychostrongyle parasites
trichostrongyloidea
in Gi tract
parasitic gastoenteritis (PGE)
diarrhea
weight-loss
in cattle
ostertagia ostertagi (brown stomach worm)
small ruminants
haemonchus contortus (barber pole worm)
ostertagia ostertagia
after ingestion at L3, larvae enter gastic gland for at least several days, then emerge into lumen and become adults
most pathogenic change-L4 emerging of the abomasal mucosa (L4 is hypobiotic), may remain as hypobiotic larvae for several months
adults not very pathogenic
impact of larvae on gastic glands
cell differentiation
hyperplasia
formation of nodules
changes to stomach function
reduction of acidity of abomasal fluid-pH increased from 2-7
failure to activate pepsinogen to pepsin
loss of bacteriostatic effect
increase permeability of abomasal epithelium
leakage of pepsinogen into circulation
loss of plasma protein
adults and immune cattle, little to no effect
light to moderate infection
subclinical, most common in US
no impact or decreased weight gain/growth from anorexia and gastric disturbance
heavy infection in young or immunocompromised animals
diarrhea
weight loss
hypoproteinemia: bottle jaw
death in weeks
heamonchus contortus
abomasal parasite of small ruminants
female up to 3cm
most important helminth in small ruminants
more pathogenic than most other trichostrongyles because blood feeding
pathogenic stage: adults
in heavier infection: haemonchus contortus
anemia-not diarrhea
anorexia
bottle jaw
weight loss
death
type 1 diease
caused by larvae that have developed without interruption
represent accumulation of adult worms during grazing season
usually occurs in late-summer or autumn in pasture young animals
any sheep or goat with anemia in the grazing season has heamonchosis until proven otherwise
