Helminths Flashcards
What are helminths?
Worms! Invertebrates, Macroparasites
What Phylum do roundworms belong to?
Nematodes
What Phylum do Flatworms belong to?
Platyhelminthes
What phylum do thorny- headed worms come from?
Acanthocephala
Platyhelminthes can be divided into 2 classes. What are they and what is the common name of those within them?
Cestodes (tapeworms) and Trematodes (flukes)
Where can you find Nematodes?
Present in every imaginable habitat. Arctic, Soil, Deep Sea, ect
TRUE or FALSE: Nematodes are Coelomates?
No they are pseudoceolomates
What is the target of antihelmintic drugs?
Nerve function. It is necessary to survival for nematodes
What are key features of nematodes?
- chitinous cuticle, presence of complete digestive system. - Sexual dimorphism, Reproduce sexually
Which nematode does not reproduce sexually?
Strongyloides
Male nematodes have what reproductive structure and what is it for?
BONUS: What is the structure made out of?
Males have copulatory bursa for grasping females, and copulatory spicules for guiding sperm.
Bonus: It is made out of a cuticle modification.
What are the 3 cuticular modifications in nematodes?
- Various size/ shape of buccal cavity
- leaf crown/ alae
- Copulatory bursa
Which nematodes have a large Copulatory bursa?
Strongyles
What is the infective state of nematodes?
L3 and sometimes L1
What is the adult stage of nematodes referred to?
L5
Where are eggs shed from the nematode in regard to the host?
L1 in feces (sometimes in urine), some dont shed at all
What is the most common migration of nematodes?
Hepatic-Tracheal migration
(ascarids)
What kind of lifecycle do nematodes have?
Direct lifecycle, indirect lifecycle, oviparous, viviparous, ovoviviparous, obligatory,
facultative
Nematode development can be completed where?
Entirely at the predilection site.
Larvae/pre-adults can also migrate during development
Nematodes that generally develop ONLY in the gut are ?
Generally asymptomatic with low pathogenicity.
Where do larvae migrate to in the case of tracheal ascarid?
Larvae will migrate to the liver, lungs, and heart.
Can cause hepatic damage, respiratory signs, lung lesions, etc.
What are critical external components for larval/ egg development?
Temperature and Humidity
What is hypobiosis?
-Inhibited larval development to avoid adverse conditions for development and
maturation – adaptation to host and environmental conditions
- Development starts once condition become favorable
Give an example of parasites with thin egg shells?
Hookworm, Strongyloides
Give an example of nematodes with thick egg shells?
Ascarids
What is periparturient?
When the immune system is compromised during parturition → increased number of eggs/larvae
What is spring rise?
Spring rise is the build of larvae of the egg during the spring
What stage of development is L5 in nematodes?
Adult
What are oncospheres?
A hatched hexacanth
Name the two morphological factors that help differentiate between Nematode eggs:
Egg shape
Egg shell thickness
How do you diagnose infections of nematodes?
- Morphological identification
- Identifying eggs/ larvae
- Molecular/ serological testing.
Where can adult Nematodes be found?
In vomit and feces.
How can you ID Nematode eggs/larvae in feces ?
Eggs = fecal smear, flotation, sedimentation
Larvae = Baermann method (larval sedimentation)
In case of Pig ascarid, larval migration from the intestine on to the liver and the lungs can cause what kind of damage to the pig?
hepatic damagerespiratory signs, lung lesions
What are the 6 major nematode orders?
- ) Strongylida
- ) Rhabditida
- ) Ascaridida
- ) Oxyurida
- ) Spirurida
- ) Adenophorea
What are some unique features of cestode anatomy?
- Flatworms - dorsoventrally flattened body.
- Tiny (2 mm) to enormous (12 m)
- Segmented body (Proglottids) 3 to 100s
- Head with suckers (slit/cup like) - attachment or Bothria
- Hemaphrodite
- Acoelomate
- Alimentary canal absent - feed by absorption
- Body covered by tegument
- Indirect life cycle
What is the segments of the cestodes body called?
Proglottids
The entire head of a Cestode is called a?
Scolex
What does the scolex give rise to?
The proglottids
How is being a hermaphrodite beneficial for Cestodes?
Cestodes can self fertilize and cross fertilize.
What does Acoelomate mean?
Lacking a coelum/body cavity.
What is the main function of the Cestodes Tegument?
The tegument’s main function is nutrient absorption.
What kind of lifecycle do cestodes have?
Indirect. Most vertebrate intermediate hosts/ some arthropods.
Describe in detail the life cycle of the Cestode.
- Larva develop into adults in the intestine of the definitive host
- Egg with hexacanth larvae form in the definitive host
- Contaminate feces (environment)
- Egg with hexacanth larvae OR gravid proglottids (environment)
- Ingested by intermediate host; eggs change into oncosphere; penetrate gut wall and reach various tissues.
- Larvae (metacestodes) form cysts in various tissues (intermediate host)
- Ingestion of intermediate host tissue with cysts containing infective larvae enter new definitive host
- Cycle starts again
What are two important orders of cestodes?
Cyclophylidea
Pseudophylidea
Within Cyclophylidea, what are the categories of tapeworms of veterinary importance?
Taeniid tapeworms:
- Taenia spp.
- Echinococcus spp.
Non taeniid tapeworms:
- Dipylidium
- Mesocestoides
- Moniezia
- Anoplocephala
What is the main difference between Taeniid tapeworms and Non-taeniid tapeworms?
Egg morphology differs.
What are the two important genus’s of pseudophylidea?
- Diphyllobothrium (fish tapeworm)
- Spirometra (tapeworm of dog, cats and wild
carnivores)
What are two important characteristics of cyclophylidea?
- Organ of attachment: Suckers
- Eggs are non operculated
What are two important characteristics of pseudophylidea?
- Organ of attachment: Bothria
- Eggs operculated
What kind of larvae do cestodes have?
hexacanth larvae
Define Hexacanth.
Hexacanth
Canth = small hooks
Hexa = 6
Usually can count 6 hooks in the egg.
What are cestodes infective larvae called?
Metacestode in final intermediate hosts.
What kind of cestode eggs are these?
All Taenia species have same egg morphology.
The eggs have an embryo with 6 hooks (hexacanth larvae) and thick straited egg shell
What is contained within each proglottid?
A male and female reproductive system
What kind of cestode eggs are these?
Operculated eggs
Diphyllobothrium and Echinococcus spp. ) have same egg Spirometra morphology – commonly called taeniid eggs. Moneizia
(note, most trematodes have operculated eggs too)
What are tapeworms named according to?
Morphology of the cyst
What are the names of tapeworms cysts?
- Cysticercus
- Cysticercoid
- Hydatid
- Coenurus
- Strobilocercus
Cysticercus – A single protoscolex in a fluid filled cyst
Hydatid cyst - Plerocercoid
- Tetrathiridum
Cysticercus is a ?
Single protoscolex in a fluid filled cyst.
Metacestodes are named according to?
Morphology of cysts.
What is the adult morphology of trematodes ?
Flat, leaf like body
Easily visible
hermaphrodite
Two suckers (Oral and ventral)
How many intermediate hosts do pseudophyllidean cestodes usually have?
2 intermediate
What kind of lifecycle do trematodes have?
Lifecycle is always indirect. Most have 2 hosts, some have 3 hosts (2 IHs)
What intermediate host must always be present in trematode lifecycles?
a snail ( terrestrial or aquatic)
What environmental factor is extremely important in the life cycle of most trematodes?
WATER
What is the name for the infective stage for most trematodes?
Metacercaria
Where do trematodes typically infect in the host?
Definitive host: may infect GI tract, Liver, Lungs, circulatory system
What kind of eggs do trematodes have?
Eggs are operculated except heterobilharzia)
What is a unique feature of fluke eggs is important to know?
It doesnt float. Sedimentation method is important
What is key morphology of acanthocephalans?
- No digestive tract, separate sexes, retractable spiny attachment (Proboscis)
What kind of lifecycle do acanthocephalans have?
indirect
what is the intermediate host for acanthocephalans
Arthropods (beetles)
TRUE OR FALSE:Ancanthocephalans are a very common group of parasites
False
In Acanthocephalans, how are nutrients absorbed?
No digestive tract. Nutrients absorbed through tegument.
Where are Acanthocephalans found?
Vertebrate digestive tracts
What is an important note for Acanthocephalan eggs?
- eggs are very heavy and contain larvae
What parasite is this?
Tapeworm
What is the image pointing at? Hint: This is a nematode
Spicule
What parasite is this cross section from?
Nematode or roundworms
What is this image of overall? What parasite is it from? and What are the red lines pointed at?
- ) Buccal Cavity
- ) Nematode
- ) Teeth
What are the projections (indicated with the black arrow) in this photo?
Cervical Ale
What kind of parasite is this?
Trematodes
What kind of parasite is this?
Thorny headed worm or Acanthocephalans
The parasite that causes these lesions can travel a considerable distance before settling in their predilection site, what are they?
Larva Migrans
What is the opening indicated by the arrow called? What is it for? What phylum and order are they found in?
Bothria
Function: Organ of attachment
Phylum: Cestode
Order: Pseudophylidea
Recap
