Platyhelminthes/cestoda: Orders Cyclophyllidea & Pseudophyllidea Flashcards
Description of platyhelminthes
Leaf-like or ribbon-like body, dorsoventrally flattened. Size: few mm to several meters.
Body cavity is missing, internal organs are in the parenchyma.
Gastrointestinal tract of most species are sac-like, missing in some.
Respiratory organs are missing. Nervous system is primitive. Mostly hermaphrodites.
Complex life cycle in - heteroxenous.
define proglottid
one of the segments of a tapeworm formed by a process of strobilation in the neck region of the worm, containing both male and female reproductive organs, and surviving briefly after breaking away from the strobila.
define strobila
a linear series of similar animal structures (as the segmented body of a tapeworm) produced by budding.
define scolex
the anterior end of a tapeworm, bearing suckers and hooks for attachment.
How do tapeworms gain nutrients?
Digestive system is missing- nutrients taken in through the tegument.
Adult tapeworms are parasites of what part of their host?
parasites of the gastrointestinal tract.
Adults cause minor harm, but larval stages are of greater significance.
define Microtrichia
Site of absorption and secretion on the tegument of cestodes.
The tegument is a massive cell that
covers the entire surface of the worm, and is thought to be an adaptation that enabled flatworms to become parasites.
Where do new proglottids form?
The neck is the budding zone, area of proliferation or area of segmentation.
Cestodes are divided into two important orders:
Order Cyclophyllidea &
Order Pseudophyllidea = Diphyllobothriidea
Cestodes are divided into Order Cyclophyllidea & Order Pseudophyllidea = Diphyllobothriidea.
What are the main differences between these?
Armed scolex with suckers vs Unarmed scolex with grooves
Proglottids with no uterine pore vs Proglottids with uterine pore
Terminal proglottids gravid vs Terminal proglottids not gravid
Mainly in terrestrial vertebrates vs Aquatic stages part in life cycle
Diheteroxen vs Triheteroxen
Genital pore on one side vs Genital pore in the middle
Selective and simplified list of platyhelminthes in systematics
Pseudophyllidean life cycle
Mature pseudophyllidean proglottids expel eggs while remaining a part of the chain
define Diphyllobothriosis
is a parasitic infection caused by cestodes of the genus, Diphyllobothrium, also known as “broad tapeworms” or “fish tapeworms”.
Flatworm, cestode = tapeworm
Latin name: Diphyllobothrium latum
English name: broad (fish) tapeworm
Diphyllobothriosis is a zoonotic parasitoses caused by cestodes from Dibothriocephalus genus and parasitizing who/what?
the small intestine of fish-eating mammals when adult and in crustaceans and fish when larva.
define paratenic host
An optional intermediate host is one which the larvae usually enters passively, along with ingested food.
Diphyllobothriosis, Hosts and transmission
Copepod = small crustacean
Three host life cycle
Marine cycle
define prepatent period
The period in a parasitic infection analogous to the incubation period of a bacterial infection, when the parasite has invaded the human host but has not yet caused pathological changes that reveal its presence by causing symptoms (ie. parasites in feces).
review
Parasite morphology: Dibothriocephalus latus
Fish tapeworm
define operculum
Operculum = A cap from which worms hatch from the egg.
Clinical signs of Diphyllobothriosis
Mostly asymptomatic, but long-lasting infection
Fatigue, abdominal pain
Vomiting, transient diarrhea, weight loss
Anemia
In humans also long-lasting
Vitamin B12 deficiency - fatigue
Anemia
Abdominal cramps
Cholecystitis
Intestinal obstruction
Epidemiology of Diphyllobothriosis
Distribution: Northern hemisphere
Global trade in wild-caught fish leads to
human cases outside of endemic areas.
How to diagnose diphyllobothriasis? (3)
detect eggs (fecal flotation etc.)
detect proglottids (feces or vomit)
molecular methods (for species determination)
identify these two
Left: Diphyllobothrium latum egg
Right: Fasciola heaptica egg
Treatment of diphyllobothriasis.
Cestocidal drugs:
Praziquantel + pyrantel
- For treating mixed infections with cestodes and nematodes
- Administered elevated doses For two consecutive days
or
Praziquantel + fendendazole + pyrantel
Effective against adult worms
Vitamin B12 replacement
Life cycle and hosts of Spirometra spp.
Final host: Dogs, cats, wild animals
Humans are paratenic hosts or II intermediate host
define bothria
are elongate, dorsal or ventral longitudinal grooves on the scolex of cestoda.
Family Anoplocephalidae belongs to which order?
Cyclophyllidea
4 important families belonging to order Cyclophyllidea:
Anoplocephalidae
Taeniidae
Dilepididae
Mesocestoididae
Cyclophyllidean life cycle:
Larval form (metacestode) in the intermediate host adult in the final host.
Cestode metacestodes are what?
they are forms of cestode larvae
Metacestode is thin-walled, fluid-filled cyst.
Small tapeworm “heads” (protoscolices) grow from inside surface: inverted protoscolex. When in the small intestine
the protoscolex everts.
Image depicts various stages of larvae.
Diagnosis of cyclophyllidean infections:
Fecal examination of microscopy is NOT reliable for cyclophyllidean infections, see image as to why.
Use antigen test instead.
cysticercoid of moniezia
(A cysticercoid is the larval stage of certain tapeworms.)
egg of moniezia
Moniezia morphology.
4 suckers
No rostellum nor hooks
Wide proglottids
Two sets of genital organs
Life cycle of moniezia expansa.
commonly known as sheep tapeworm or double-pored ruminant tapeworm.
Clinical signs of monieziosis.
Mostly benign
Signs are more seen in young animals
M. expansa: massive infections
Reduced weight gain in lambs
Reduced productivity
Poor hair coat
Constipation or diarrhea
Intestinal obstruction
Neural signs - enterotoxemia
Coinfection with roundworms
M. benedeni: little pathogenic
Diagnostic methods for detecting moniezia spp. (4)
detect eggs (flotation)
detect adults or proglottids
detect antibodies
molecular methods (PCR)
Control and prevention of monienzia spp.
Control is difficult: Prevalence of grain mites is huge.
In endemic zones:
- Harvest the hay
- Deeply plow the fields
- Reseed fields
Mites active:
Early in the morning and at nightfall
Metaphylactic deworming
- Do a fecal egg count (FEC)
- Deworm 1 month after grazing
“Clean” or “Safe” pasture management
Clean: 3 years no grazing by ruminants
Safe: variable
Hosts and transmission of Anoplocephala and Paranoplocephala.
Final host: Horse, donkey
Intermediate host: forage mite (Oribatidae)
Intermediate stage, II stage larva: cysticercoid
Transmission:
ingestion of cysticercoids in mites
Location in the horse as an adult:
A. magna: small intestine, (stomach)
P. mamillana: small intestine
A. perfoliata: terminal ileum, caecum, ileocecal junction/valve
Morphology of Anoplocephala and Paranoplocephala.
4 suckers
No rostellum or hooks
Proglottids wider than long
identify Anoplocephala/Paranoplocephala spp.
A. perfoliata
A. magna
P. mamillana
Life cycle of Anoplocephala and Paranoplocephala.
Pathogenesis of Anoplocephala and Paranoplocephala.
Relatively non-pathogenic but heavy infections are serious. Attaches to mucosa.
A. perfoliata colonizes around the
ileocecal junction causing Peristalsis disorders.
- Ulceration
- Intussusception
- Ileal impaction
- Spasmodic colic
Haemorrhagic enteritis results.
Clinical signs of anoplocephalidosis.
Especially in foals, young horses,
animals with health problems.
Light infection: No clinical signs
Heavy infection:
GI disturbances – colics
Anemia
Diarrhea
Death (intestine wall perforation)
Diagnostic methods for detection of anoplocephala. (5)
detect eggs (flotation)
detect adults/proglottids
detect Ab’s
radiology (sheer mass of infestation causing obstruction)
rectalization (mass in ileoceceal region)
Prevention and control of anoplocephalodioses.
Control is difficult as mites are widespread on pastures.
Metaphylactic deworming
- 1-2 times per year
Or Previous examination of feces - fecal egg count (FEC) and deworming based on results.
