Platyhelminthes 1 Flashcards
What are platyhelminths?
Flatworms
Two different types of platyhelminths
- Cestodes = tapeworms
- Trematodes = flukes
Cestodes are divided into:
- Cyclophyllidea
- Pseudophyllidea
Cestodes are
tapeworms
Trematodes are
flukes
Body of platyhelminthes is
Leaf-like or ribbon-like
Dorsoventrally flattened
Few to several meters long
Body cavity of platyhelminthes
Is missing, organs are in parenchyma
GI tract sac-like or missing
Respiratory organs missing
Nervous system primitive
Mostly hermaphorides
Life cycle of platyhelminths
Complex - heteroxenous
What are cestodes?
Tapeworms
What are the segments in cestodes called?
proglottids
Each proglottid has a set of organs, mostly reproductive
Proglottids grow from the neck area
In a cestode, proglottids for a…
Strobila (chain)
The anterior part of the body in cestodes is called…
scolex (head)
Reproduction in cestodes?
Hermaphrodites
Digestive system in cestodes?
Missing, nutrients taken through the tegument (site of absorption and secretion)
Life cycles in cestodes?
Complex, heteroxenous
Which place(s) do adult cestodes parasitise
Gastrointestinal tract
Which are more harmful: larvaes or adult cestodes?
Larval stages are more harmful
What is the tegument?
A massive cell that covers the entire surface of the worm. Place of absorption and secretion
Differences between cyclophyllidea and pseudophyllidea: scolex
Cyclophyllidea: Scolex has 4 suckers, can have rostrellum (spikes)
Psudophyllidea: No suckers, but suctorial grooves (bothria)
Differences between cyclophyllidea and pseudophyllidea: segments
Cyclophyllidea: uterus fills the whole segment. Genital pore is located laterally, no uterine opening
Pseudophyllidea: Uterus is coiled medially. Genital pore and uterine opening are medio-ventrally located.
Differences between cyclophyllidea and pseudophyllidea: life cycle
Cyclophyllidea: mainly in terrestrial vertebrates
Pseudophyllidea: aquatic stages are part of life cycle
Two pseudophyllideas that we study:
Diphyllobothrium latum = broad (fish) tapeworm
Spirometra spp. = zipper tapeworm
Diphyllobothriosis general description
Diphyllobothriosis is a zoonotic parasitoses caused by cestodes from Dibothriocephalus genus and parasitizing the small
intestine of fish-eating mammals when adult and in crustaceans and fish when larva.
Diphyllobothrium latum hosts
- intermediate host: Copepod (body cavity)
- intermediate host: Fish, amphibians and reptiles (muscles, tissues)
Paratenic host: Predatory fish
Final host: Fish-eating mammals, birds, humans (in the small intestine)
Life cycle of Diphyllobothrium latum
“Three host life cycle”, marine cycle
- Unembryonated eggs are passed in feces
- Eggs are embryonated in water
- Eggs hatch and are ingested by copepod
- Larvae are developed in copepod
- Copepod is ingested by small fish
(6. Predator fish eats small fish) - Definitive host eats fish
- Larva develops into adult in the small intestine
Diphyllobothrium latum morphology
Up to 20m
Elongated scolex with two bothria (grooves)
Proglottids are wide and short
Uterine pore is present
Uterus coiled in the centre
Diphyllobothrium latum egg morphology
Have operculum and small knob
Form: oval
Content: yolk and egg cell(s)
Shell: medium thick
Diphyllobothrium latum clinical signs
Mostly asymptomatic, but long-lasting infection
Fatigue
Abdominal pain
Vomiting
Transient diarrhea
Weight loss
Anemia
B12 insufficiency
Diphyllobothrium latum diagnostic methods
Detecting eggs:
Feacal flotation
Sedimentation
Detecting proglottids:
In feces or vomit
Molecular method:
Species determination
Prevention of Diphyllobothrium latum
Fish should be frozen or cooked
Other name for Spirometra spp.
Zipper tapeworm
Spirometra spp. hosts
Final hosts: Dogs, cats, wild animals
Humans are paratenic host or 2. intermediate host
Life cycle similar to Diphyllobothrium
Differences between pseudophyllidea and cyclophyllidea: shedding eggs
Pseudophyllidea: Gravid proglottis releases eggs inside the host. Eggs are shed via feces
Cyclophyllidea: Gravid proglottis separates from the chain and reaches the environment. Is muscular and can crawl. Eggs will be released
Life cycle of cyclophyllideans
- Adult is in the small intestine
- Gravid proglottis separates and reaches the environment –> releases eggs
- Eggs have already larva (oncosphere) inside and are immediately infective
- Intermediate host ingests egg and larva hatches
- Larva migrates to predilection site and transforms into larval tapeworm - metacestode
- Metacestode developes and waits inside the intermediate host to be eaten by final host
What is a metacestode?
Form of a cestode larvae
Thin-walled fluid-filled cyst which has small tapeworm “heads” growing on the inside surface.
Can have many different forms and can be present around the body i.e. brain, liver, muscle
What is different in diagnosing cyclophyllidean infections compared to pseudophyllidean?
Faecal examination by microscopy is not reliable since eggs are usually released after the tapeworm segment has exited the host and eggs will not be seen.
Detection of antigen or DNA in faeces is a better option.
Moniezosis parasite(s), latin and english
Moniezia expansa - sheep, goat, (cattle)
Moniezia benedeni - cattle, (sheep, goat)
Double-pored ruminant tapeworm
Moniezosis general description
Monieziosis is a parasitoses caused by
cestodes from Moniezia genus, parasitizing
the small intestine of ruminants when
adult and forage mites when larva.
Moniezia hosts, larva, transmission
Final host: ruminants (in the small intestine)
Intermediate host: forage mites
- larval stage: cysticercoid, develops in the intermediate host
Transmission: ingestion of forage mite with larva
Moniezia morphology
M. benedeni lenght 0,5-4m
M. expansa lenght 4-10m
4 suckers
No rostrellum or hooks
Wide proglottids
Twi sets of genital organs
Moniezia egg morphology
Shape: triangular (m. expansa) or cube-shaped (m. benedeni)
Content: 1. larval stage
Moniezia life cycle
Indirect - two hosts
1. Parasite sheds proglottids in the final host
2. Mite ingests the eggs
3. Cysticercoid develops in mite body 2-4 months
4. Larva develops into adult in the final host
5. Adult starts to shed eggs 6-10 weeks after
infection
Moniezia clinical signs
Mostly benign, clinical signs in young animals
M. expansa: massive infections
General signs
Constipation or diarrhea
Intestinal obstruction
Neural signs (enterotoxemia)
Moniezia epidemiology
Worldwide
Seasonal fluctuation
Natural pasture
Highest infection: autumn
Lowest infection: summer
Moniezia diagnostic methods
Detecting the eggs:
Fecal flotation
Easily detectable eggs
Detecting adults or proglottids:
Necropsy - adults in intestines
Proglottids in feces
Antibodies: serology
Molecular methods: PCR
Moniezia prevention
Prevalence of grain mites is huge, difficult to control
Metaphylactic deworming
“Clean” or “safe” pasture management (no grazing for 3 years)
Anoplocephalidosis parasite(s)
Horse tapeworm
Two genera: anoplocephala and paranoplocephala
Anaplocephala perfoliata
Anoplicephala magna/plicata
Paranoplocephala mamillana
Anoplocephalidosis general description
Anoplocephalidosis is a parasitoses caused
by cestodes from Anoplocephala and
Paranoplocephala genera, parasitizing the
small intestine of horses when adult and
forage mites when larva.
Anoplocephala hosts, larva, transmission
Final host: horse, donkey
Intermediate host: forage mite
Intermediate stage, 2. larval stage: cysticercoid
Transmission: ingestion of cysticercoids in mites
Anoplocephalas, location in the horse as adult
A. magna: small intestine, (stomach)
P. mamillana: small intestine
A. perfoliata: terminal ileum, cecum, ileocecal junction
Anoplocephala morphology
4 suckers
No rostrellum or hooks
A. perfoliata lenght 2,5-8cm
Anoplocephala life cycle
Two hosts
1. The parasite lays eggs in the final host
or expels proglottids in the faeces.
2. Eggs are swallowed by the mite, the
intermediate host.
3. The egg develops into a cysticercoid
4. The mite is eaten by the final host
5. The cysticercoid is released and
attaches to the mucous membrane
6. An adult tapeworm develops and lays
eggs
Anoplocephala pathogenesis
Relatively non-pathogenic
Heavy infections are serious
A. perfoliata attaches to mucosa around the ileocecal junction
-Peristalsis disorders
-Intussusception
-Ilea impaction
-Spasmodic colic
-Hemorrhagic enteritis
Anoplocephala clinical signs
Especially in young or sick horses
GI disturbances - colics
Anemia
Diarrhea
General signs
Death (in case of intestine wall perforation)
Anoplocephala epidemiology
Prevalent worldwide, a. perfoliata more prevalent
All ages affected, clinical cases in young
Seasonal fluctuation: highest in winter and early spring
Anoplocephala diagnostic methods
Detecting eggs:
Faeces flotation method
Adults or proglottids: feces or necropsy
Serology
Radiology (intestinal obstruction)
Rectal examination: firm mass in ileocecal region
Anoplocephala prevention
Mites are widespread in pastures, control difficult
Metaphylactic deworming
Good pasture/manure management
