Intro to Helminths Flashcards
Are helminths ecto or endoparasites?
Endoparasites
- acanthocephala
- nematoda
- platyhelminthes
- cestoda and trematoda
________ and _______ are long, non segmented
Acanthocephalan and nematode
Cestodes have ______ bodies
Long, segmented
- flat
Trematodes are _______ shaped
Leaf-like/petal shaped
- flat
Acoelomate
All parenchyma, no body cavity
- trematodes
- cestodes
Pseudocoelomate
Have a body cavity, but the mesoderm does not coat the organs (are more likely to move around)
- nematodes
- acanthocephalans
Trematodes have a _____ digestive tract
Partial
- cecum does not have a direct opening to the outside
Cestodes have _____ digestive tract
No!
- no mouth opening = no digestive tract
- acquire nutrients via absorption thru integument
Nematodes have a ________ digestive tract
Complete
- feeding mechanism with an excretory system
Dioecious
Split, separate sexes
- clear male and female with their own repro organisms
- thorny headed worms and nemotodes
- males smaller than females
- heartworm males have a coiled tail and are smaller
Monoecious
Hermaphrodites
- one body system, one set of repro organisms
- cestodes: every segment is its own living entity
- trematodes: contain both sets of repro tracts
General characteristics of nematodes
- long, round, unsegmented
- pseudocoelomate
- complete digestive tract
- dioecious
(barber pole worm)
General characteristics of cestodes
- long, dorsoventrally flat, segmented
- acoelomate
- lack digestive tract
- monoecious
General characteristics of trematodes
- dorsoventrally flattened, unsegmented
- acoelomate
- incomplete digestive tract
- monoecious
What is the one exception of monoecious trematodes?
Schistosomes
- present in dogs, male and females are separate, but they have a close relationship
- females lie in canal of the male
- usually found in veins
General characteristics of acanthocephalans
- long, round, unsegmented
- pseudocoelomate
- lack digestive tract
- dioecious
No body cavity, solid with embedded structures, body usually flattened
Cestodes and Trematodes
Body cavity, coelom or pseudocoelom, body usually cylindrical
Acanthocephala and nematoda
Anterior end armed with proboscis, no digestive tract
Acanthocephala
No proboscis, digestive tract present
Nematoda
No digestive tract, segmented body
Cestoda
Digestive tract, no segmentation
Trematoda
Acanthocephala
Thorny headed worms
- long, cylindrical
- anterior spiny proboscis
- no digestive tract
- pseudocoelomates (hydrostatic system)
Hydrostatic system
Pushes proboscis in and out
- if the worm is in the intestine, then the thorny head is used for attachment = lesion that goes thru the intestine (peritonitis)
Acanthocephalans are _______
Dioecious
- female is larger!!
General acathocephalan life cycle
Mature adults in DH intestine, produce eggs –> eggs shed in feces –> eggs in environment, contain acanthor –> IH ingests eggs with acanthor –> acanthor (infective stage) –> acanthella –> cystacanth (infective stage for definitive host) –> DH ingests IH
Acanthocephalans cause disease due to their _____
Proboscis
- amount of inflammation or other damage depends on various factors (inclu proboscis morphology)
- clinical signs are rare unless perforate intestines
Macracanthorhynchus hirudinaceus
- DH: swine
- IH: grubs (larvae)
- -> dung beetle, may beetle, water beetle (also adult beetles)
- may be zoonotic
M. hirudinaceus life cycle
DH: adult worms in SI –> eggs in environment –> IH: dung beetles –> DH ingests IH
- PPP: 2-3 months
M. hirudinaceus pathogenesis and clinical signs
Usually asymptomatic
- possible GI signs
- enteritis/pain, decrease feeding or weight gain, diarrhea
M. hirudinaceus diagnosis
Eggs in pig feces, requires dense, high SG float solution
- almond shaped
- multiple layers
- dark brown
Recovery adult throny-headed worms at necropsy
Must differentiate M. hirudinaceus from _______
Ascaris suum (nematode) - look for proboscis
M. hirudinaceus treatment and control
No approved anthelmintics
- ivermectin, some benzimidazoles
- control intermediate hosts
- regular disposal of feces
Macracanthorhynchus ingens
DH: mainly raccoons IH: milipedes - similar life cycle to M. hirudinaceus - no clinical signs - off-label treatment (ivermectin)
Must differentiate Macracanthorhynchus ingens from
Cestodes
- ex: taenia spp in dogs
- also some large nematodes