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
Prevention of diphyllobothriasis
Reinfection is likely to occur.
Fish should be frozen or cooked.
- 20° C or below for 7 days
- internal temperature of ≥ 63°
Infected human or animal feces should not get into bodies of freshwater.
Sushi is a risk!
Describe Spirometra spp.
Spirometra mansonoides
S. erinaceieuropaei
English name
zipper tapeworm
In humans infection is called sparganosis.
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.
define protoscolice
just a juvenile scolex (parasite head)
but these are inverted on the inside of the larvae and this changes when the larvae develops into adult form.
Diagnosis of cyclophyllidean infections:
Fecal examination of microscopy is NOT reliable for cyclophyllidean infections, see image as to why.
Use antigen test instead.
define monieziosis
Ruminant tapeworm
monieziosis is caused by
Moniezia expansa – sheep, goat, (cattle)
Moniezia benedeni – cattle, (sheep, goat)
Double-pored ruminant tapeworm
Monieziosis is a parasitoses caused by
cestodes from Moniezia genus, parasitizing
who or what?
the small intestine of ruminants when
adult parasites, and inhabit forage mites when larva.
Moniezia expansa – sheep, goat, (cattle)
Moniezia benedeni – cattle, (sheep, goat)
Hosts and transmission on monieziosis.
Final host: ruminants (In the small intestine)
Intermediate host: forage mites (genus Oribatidae)
- Live in the soil, on grass, plants, very prevalent.
II larval stage: cysticercoid
Transmission: Ingestion of forage mite with larva
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
Epidemiology of moniezia spp.
Distribution: Worldwide, Seasonal fluctuation
Natural pasture
Highest infection rates in autumn
Lowest infection rate in summer
Prevalent in young lamb, kids, calves
Sheep more susceptible
During first summer on pasture
The larva can winter successfully in forage mites.
Diagnostic methods for detecting moniezia spp. (4)
detect eggs (flotation)
detect adults or proglottids
detect antibodies
molecular methods (PCR)
Treatment of moniezia spp.
Cattle usually do not need treatment.
Sheep is treated in late spring or early summer. Next treatment in the autumn.
Cestocidal drugs effective:
Albendazole
Fenbendazole
Niclosamide
Praziquantel+levamisole
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
english name for anoplocephalidosis
horse tapeworm
Horse tapeworm genera (2)
Genera: Anoplocephala and Paranoplocephala
but are basically consideered as one because they don’t have major differences.
Species:
Anoplocephala perfoliata
Anoplocephala magna/plicata
Paranoplocephala mamillana
Anoplocephalidosis is a parasitoses caused
by cestodes from what egnera?
Anoplocephala and
Paranoplocephala genera, parasitizing the
small intestine of horses when adult and
forage mites when larva.
Anoplocephalidosis is a parasitoses caused
by cestodes from Anoplocephala and
Paranoplocephala genera, parasitizing who/what?
the small intestine of horses (and donkeys) when adult and forage mites when larva.
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
Which Anoplocephala spp. is most pathogenic?
Anoplocephala perfoliata
(can perforate parts of the host GI tract)
This one also happens to resemble a fluke even though its a cestode.
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)
Epidemiology of anoplocephalidosis.
Distribution: worldwide. A. perfoliata most prevalent.
All ages affected, Clinical cases in younger animals.
Seasonal fluctuation and grazing season.
The presence of mature tapeworms in the intestines is highest during winter and early spring.
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)
Treatment of anoplocephalodioses.
Surgery when ileal impaction or ileocecal intussusception.
Anticestodal treatment after surgery.
Cestocidal drugs: Usually with higher dosages
- Praziquantel + moxidectine
- Praziquantel + ivermectin
- Pyrantel (Increased dosages needed, Only effective against P. perfoliata)
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.
Most important things to remember about horse tapeworms? (4)
Anoplocephala perfoliata can cause colic in the ileocecal region.
Lesions can include ileal impaction and ileocecal intussusception.
Can be a cause of spasmodic colic.
Egg-counting techniques can detect larger infestations.
