Platyhelminthes/cestoda: Order Cyclophyllidea, Family Taeniidae Flashcards
Cestodes are divided into two important orders
Pseudophyllidea
Cyclophyllidea
metacestode
Larval form (metacestode) in the intermediate host (adult form in the final host).
Metacestode structure
Metacestode is a thin-walled, fluid-filled cyst.
Cestode metacestodes are a form of cestode
LARVAE.
Small tapeworm “heads” (protoscolices) grow from the inside surface as an inverted protoscolex.
When in the small intestine the protoscolex everts.
Which has a longer path to adult form - pseudophyllidea or cyclophyllidea?
Cyclophyllidea has a bigger variety for path to adult form.
Taeniosis (or taeniasis) is a
parasitosis caused by adult parasites of Taeniidae family and genus
Taenia in final hosts that are carnivores.
Cysticercosis and coenurosis are
parasitoses caused by larval stages of parasites of the genus Taenia in the intermediate hosts, that are ungulates, ruminants, rodents and other mammals.
taeniosis and cysticercosis difference
taeniosis is caused by adult form taeniae
cysticercosis is caused by larval stages of taeniae in intermediate hosts.
Taenia species infecting humans and
farm animals: (2)
Taenia solium (pork tapeworm)
Taenia saginata (beef tapeworm)
Taenia Species infecting dogs: (5)
- Taenia ovis
- Taenia hydatigena
- Taenia pisiformis
- Taenia multiceps
- Taenia serialis
Taenia Species infecting cats: (1)
- Taenia taeniaformis
6 types of cyclophyliidean metacestode:
cysticerus
coenurus
strobilocercus
cysticercoid
hydatid cyst
alveolar cyst
define cysticerus
a type of cyclophyllidean metacestode
is a fluid filled cavity lined by a delicate parasitic membrane that has just one easily visible solid protrusion (a single inverted tapeworm head)
define coenurus
a type of cyclophyllidean metacestode
a coenurus is like a cysticerus but there are multiple (typically dozens) of inverted tapeworm heads that appear as whitish spots on the parasitic membrane
define strobilocercus
a type of cyclophyllidean metacestode
this consists of a single tapeworm head which is separated from its parasitic bladder by a chain of segments. The whole is folded up to form a pea-szied sphere.
This type of metacestode occurs only with the cat tapeworm T.taeniaeformis.
Adult tapeworm morphology generally consists of: (3)
4 suckers
One set of genital organs
Genital pore on one side
Depending on the spp. the head may or may not have a rostellum, hooks etc.
Important to differentiate
species infecting humans, T. solium
and T. saginata.
What are their morphological differences?
T. solium (pork tapeworm):
has a rostellum with hooks.
T. saginata (beef tapeworm):
has NO rostellum nor hooks.
See image: the protrusion is the rostellum on the T.solium.
Describe the morphology of Eggs of the Taeniidae family:
Shell: Thick, Bilayered shell which is radially striped.
Content: larva (oncosphere)
hooks (3 pairs)
Size: 20-40 microm.
Taenia species life cycle
Predator-prey relationship:
Carnivores/omnivores are final hosts while
Ungulates/rodents are intermediate hosts.
- Adults live in carnivore intestines
- Proglottids shed in their feces. Eggs get out of proglottids.
- Intermediate hosts ingest the eggs
or proglottids. - Eggs hatch in the small intestine. Oncosphere migrates to tissues. Larva becomes infective in 1-3 months.
- Final host can get the infection after
ingestion.
Prepatent period 2-3 months
Patent period 1-25 years
Taenia species :
Prepatent period
Patent period
Prepatent period 2-3 months
Patent period 1-25 years
Taenia saginata (beef tapeworm),
life cycle?
Transmission to final host:
Eating raw beef contaminated with
cysticercus (metacestode form).
Transmission to intermediate host:
* eating eggs/proglottids on pasture
* feeding milk contaminated with eggs
to calves
How eggs reach the pasture? ->
Direct, indirect, birds
Taenia saginata (beef tapeworm),
Final host:
Intermediate host:
Metacestode form:
Final host: humans
Intermediate host: ruminants
Metacestode: cysticercus
Taenia saginata cysticercosis is..?
T. saginata larval stage infection in bovine
(called Cysticercus bovis previously).
- Cysticercuses found in heart, masseter m., tongue, triceps, diaphragm.
- 1x0,5cm size
- Takes 3-4 months to become
infective - Calves can have lifelong infection
- In adult cattle the cysts calcify
- Discovered during meat inspection
Taenia solium (pork tapeworm),
life cycle?
Transmission to final host:
Eating raw pork contaminated with
cysticerci (pl. of cysticercus).
Transmission to pigs:
Eating eggs, proglottids
Transmission to humans, intermediate host:
* eating eggs/proglottids
* reverse peristalsis/ vomiting - eggs hatch in the small intestine
Taenia solium (pork tapeworm),
Final host:
Intermediate host:
Metacestode form:
Final host: humans
Intermediate host: pigs, humans,
dogs
Metacestode: cysticercus
Taenia solium cysticercosis is..?
Pork tapeworm metacestode infection in In intermediate hosts.
So, T. solium larva in pigs and humans.
(called Cysticercus cellulosae previously)
- Found in muscles, skin, eyes, brain.
Cysticercosis usually has no symptoms.
But brain neurocysticercosis can cause
- Headache
- Confusion, lack of attention
- Seizures
T. solium ja T. saginataepi demiology
Worldwide prevalence, also in Estonia.
Cysticercosis is mainly prevalent in places where pigs roam freely.
Taenia in dogs (5)
Dogs as final hosts.
Prey animals as intermediate hosts (dog eats prey animal).
Adult tapeworms 0,5 cm - 5m long.
Less pathogenic to dogs.
Prepatent period 1-2 months.
Taenia ovis is Similar to..?
T. saginata (beef tapeworm)
Has a Dogs-sheep cycle
Causes Cysticercus in sheep muscles
Taenia hydatigena host cycle?
Dog-sheep cycle
Causes Cysticercus in sheep liver
parenchyma.
Liver cysticercosis as well, which resembles acute fasciolosis .
Taenia pisiformis host cycle?
Similar to T. hydatigena (which is dog-sheep).
Pisiformis has a Dog-rabbit cycle.
The most prevalent Taenia species in
dogs?
Taenia multiceps is the most prevalent Taenia species in dogs.
- The most pathogenic Taenia in sheep
- Dog-sheep and other animals,
including humans “cycle”. - Causes coenurus in sheep/human brain.
Taenia serialis host-cycle?
dogs/foxes - rabbits cycle
Causes coenurus in muscles.
Which Taenia species affects cats?
Host-cycle?
Causes what disease?
Taenia taeniaeformis
Cat-rodent cycle
- Less pathogenic to cats
- Up to 70cm in length
- Causes strobilocercus in mouse liver
A cysticercus is a
single fluid-filled cyst or bladder containing an attached single invaginated scolex (protoscolex).
Cysticercosis (metacestode cysticercus) can be caused by which T. species? (5)
T. solium,
T. saginata,
T. ovis,
T. hydatigena,
T. pisiformis
(Coenurosis (metacestode coenurus) caused by T. multiceps, T. serialis)
Coenurosis (metacestode coenurus) caused by which T. spp.? (2)
T. multiceps, T. serialis
(whilst cysticercosis is caused by the 5 other ones (solium etc.))
Clinical signs of metacestode infestation.
Signs occur during the larva migration!
Inflammation.
Place/number of larvae important influencers.
In which species and organs are the following T. spp. metacestodes forms/ cysticercosis found?
T. solium
T. saginata
T. ovis
T. hydatigena
T. solium in pigs mostly in skeletal muscles and heart (liver, brain).
T. solium in humans in subcutaneous tissues, muscles, eyes, brain.
T. saginata in bovine and T. ovis in sheep muscles.
T. hydatigena in mouse body cavity or liver.
In which species and organs are the following T. spp. metacestodes forms/ coenurosis found?
T. multiceps
T. serialis
T. multiceps,sheep, in brain, eyes – brain coenurosis
T. serialis, rabbits, in subcutaneous tissues, muscles.
Coenurus is similar to cysticercus,
but
bigger and with numerous invaginated scolices attached to the cyst wall.
Clinical signs of T. multiceps in brain aka brain coenurosis.
Neurological signs (circling, aimless running, cramps).
Transmission from eating intermediate hosts heads.
Echinococcosis is a
parasitosis caused by cestodes of the
Taeniidae family and Echinococcus genus, where carnivores act as final hosts and herbivores act as intermediate hosts.
name 2 most important echinococcus spp.
Echinococcus granulosus
& E. multilocularis
What disease do each respective spp. cause:
Echinococcus granulosus
& E. multilocularis
Echinococcus granulosus causes Cystic echinococcosis.
E. multilocularis causes alveolar echinococcosis.
E. granulosus:
size
alt. name
intermediate host
diseases caused in intermediate host (3)
2-7mm
Dwarf dog tapeworm
intermediate host, humans
in humans causes:
Cystic echinococcosis
Hydatid disease
Unilocular echinococcosis
Echinococcosis granulosus,
Final hosts: (2)
Intermediate hosts: (7)
Metacestode form:
Final host: dog, wolf
Intermediate hosts: sheep, goat, cattle, horse,
pigs, cervids, humans
Metacestode: hydatid cysts
Describe E. granulosus metacestode
Hydatid cyst – large, fluid-filled complex cyst
which has several thousands protoscolices.
floating daughter cysts can Later develop freely inside of the hydatid cysts.
The Cysts are Usually single discrete cysts,
up to size of an egg found In liver, lungs mainly.
Outer shell is strong and non-transparent, Grow irregularly.
Less severe disease in intermediate hosts.
E. multilocularis size and alt. name.
E. multilocularis is 1-5mm.
Also called Alveococcus tapeworm.
E. multilocularis,
Final hosts:
Intermediate hosts:
Metacestode form:
Final hosts: red- and polar foxes, wolf, dog, cat
Intermediate hosts: mice, rats, small mammals, human, monkey, horse,
pig, dog, etc.
Metacestode form: alveococcus
The following diseases are caused by?
In the intermediate hosts
Alveolar echinococcosis
Alveolar hydatid disease
Multilocular echinococcosis
Multivesicular hydatidoses
Echinococcus multilocularis
Describe the E. multilocularis metacestode.
Alveococcus – small cysts with jelly-like
filling, exogenic budding of new
daughter cysts.
Cysts are polycystic and found in the liver, seldom in other places. Semi translucent cystic bladder.
Infection may spread in the organism and can cause very severe disease which is difficult to treat.
How would you differentiate between E. granulosus and E. multilocularis cysts?
E. granulosus has large, fluid filled hydatid cysts. Inside them daughter cysts develop.
E. multilocularis has alveococcus which are small cysts with jelly-like filling. The daughter cysts of these are budded off exogenically.
Do not confuse Taenia hydatigena with the
hydatid cyst. They are not connected!
The metacestode of T. hydatigena is a cysticerus (not a hydatid cyst).
The hydatid cyst is the metacestode of Echinococcus grranulosus.
The hydatid cyst is the metacestode of what spp.?
Echinococcus grranulosus
Morphology of Echinococcus spp.
Scolex with 4 suckers and hooks
NB: eggs are morphologically
indistinguishable from other eggs of
Taeniidae family.
Which is bigger E. granulosus or -multilocularis?
granulosus is bigger
Life cycle of Echinococcus spp.
Can be domestic or sylvatic (wild) cycles.
Uses Two hosts
- Carnivores shed proglottids
- Herbivores ingest eggs/proglottids
- Released oncospheres migrate from
intestines to internal organs
- 6-15 months metacestodes develop
- Infectious for years
- Final host eats the intermediate host with metacestode
- Develops to adult in the small intestine of the final host
Echinococcus spp.
Prepatent period
Patent period
Prepatent period 1-2 months
Patent period 3-6 months
Resistance of Echinococcus eggs to environmental factors.
Echinococcus presence in Finland
E.Granulosus is found in wolves
E.Multilocularis is NOT present
echinococcus cysts grow to what size?
echinococcus cysts grow endlessly
Cystic echinococcosis found in what organs
Found Mostly in liver and lungs
Clinical signs of echinococcosis
Final host seldom or no signs.
Intermediate host: signs dependent on number, location, size, growth rate of the cysts.
Disturbances in lung, liver functional.
Mostly asymptomatic in farm animals.
Signs more often seen in horses.
Progress fast in rodents.
When cysts rupture, allergic reaction / anaphylaxis.
Alveolar echinococcosis found in what organs
First in liver – infiltrate. Then spreads to other organs. -> Metastases to nearby organs.
Alveolar echinococcus Infection in
humans.
Asymptomatic course with long incubation time (5-15 years).
Later liver symptoms
- pain in upper belly,
- jaundice,
- emaciation
Cancer like growth
Mortality in untreated patients > 94%
Spontaneous healing very rare.
Taeniidae family cestode eggs are morphologically…?
indistinguishable.
Diagnostic methods for taeniosis and echinococcosis
Diagnosis of Echinococcus in dogs.
eggs are not always present in feces
coproantigen or DNA tests are more satisfactory
the adult worm is very small and has its head buried in GI tract wall so microscopic inspection of mucosal scrapings is needed for detection.
Treatment options for taeniosis and
echinococcosis in final host.
In the Final host (e.g. dog): Praziquantel, fenbendazole,
epsiprantel.
Treatment should be done in quarantine - 3 days!
- Removal on feces!(burning)
- Wash the dog
- Clean the environment
- Zoonosis - protective clothing!
Primary goal of treatment is to halt the environmental contamination with Echinococcus eggs.
Treatment options for taeniosis and
echinococcosis in intermediate host.
scheme for individual deworming of cats:
indoor cats
outdoor cats
indoor cats: infection pressure low. fecal exam 1-2 times/ tear OR treat 1-2 times/year against roundworms.
outdoor cats: infection pressure high.
fecal exam or treatment min. 4x year.
Prevention measures of taeniosis and
echinococcosis for humans.
Cook your meat thoroughly.
Avoid direct contact with wild animals, especially foxes.
Good hygiene!
Clean your dog’s feces up!
Prevent infection in animals to prevent infection in humans. Treatment of imported dogs.
Prevention measures of taeniosis and
echinococcosis for animals.
Prevent infection in final host (e.g. dog).
DO NOT FEED RAW MEAT TO DOGS OR CATS (nor carcasses and rodents)
Prevent dog and cat contact with farm animals and wild animals.
Animals should not be exposed to human feces!
Dipylidiosis is a
parasitosis caused by a cestode of
Dipylidiidae family, which final host are carnivores and intermediate hosts fleas, lice.
3 alt. names for Dipylidium caninum
„Flea tapeworm“
„cucumber seed tapeworm“
„double-pored tapeworm“
„Flea tapeworm“
„cucumber seed tapeworm“
„double-pored tapeworm“
also known as? (latin)
Dipylidium caninum
Dipylidium caninum,
Final host:
Intermediate hosts:
Metacestode form:
Final host:
Dogs, cats, wild carnivores, humans
Intermediate hosts: Fleas, lice
Metacestode: cysticercoid
Morphology of dipylidium canium.
20-70cm (3mm wide) yellowish white
4 suckers, rostellum with hooks
Proglottids posteriorly longer
- cucumber seed shape.
Two sets of genital organs
Two genital openings
-No uterine pore
Morphology of dipylidium canium Egg packets:
5-50eggs (200 µm)
Shell: thin membrane + thick shell
Inside: oncosphere (larva)
Shape: oval to round
Size: 25x50µm
Life cycle of dipylidium caninum:
Two host life cycle:
- Proglottids into the environment
- Proglottids dissolve and eggs get
out.
- larva of a flea/louse eats the eggs
- Inside flea, the oncosphere
hatches and moves to body cavity. - Around 1 month cysticercoid
develops. - Final host get infections from
eating infected fleas.
Prepatent period 1 month
Patent period 3 years
Epidemiology of dipylidium caninum:
Worldwide, Common in Estonia.
More common in free-roaming
animals.
In humans: problem in children.
Important to control fleas!
Clinical signs of dipylidium caninum.
Mostly asymptomatic.
Itching in perianal region, Dogs may scoot
Rarely diarrhea
Loss of appetite, weight loss
Diagnostic methods for dipylidium caninum.
Proglottids in perianal region/feces
- soak the proglottids in water
- place between two microscopy glasses to break open
- two sets of genital organs
- inside egg packets
Detecting the eggs
- flotation/sedimentation
- egg packets
- false negatives common, not reliable
Main Difference between Taeniae eggs and Dipylidium eggs?
Taenia eggs
- typically spherical or oval in shape.
- are separate (not packets)
- have a thick, radially-striated outer shell
Dipylidium eggs
- usually more elongated and described as cucumber seeds.
- often found in packets, with multiple eggs adhering together in a group
Treatment and Prevention of Dipylidium caninum
Treatment needed when infection is
confirmed.
Ingredients active against Dipylidium include
Praziquantel, epsiprantel. E.g. drontal.
Prepatent period is short so reinfection is likely. Thus prophylactically control of fleas and lice:
- Frontline (Fipronil)
- Advantix (imidacloprid and permethrin)
permethrin and cats
permethrin, synthetic insecticide, is used in dogs against fleas.
is very TOXIC in cats!
Anticestodal or anti-platyhelmintic drugs are used to treat
tapeworm infection.
They may be either taeniafuges (which facilitate tapeworm expulsion from the host) or
taeniacides (which cause death of the tapeworm in the host).
Some of the broad spectrum benzimidazoles are also effective against tapeworms.
Name 3 Anticestodal drugs
Bunamidine
Niclosamide
Praziquantel
Describe Bunamidine:
Used mainly for Echinococcus granulosus and Taenia hydatigena.
Used as tablets (small animals) or suspensions (ruminants) for oral administration.
Mode of action: disrupts tapeworm’s tegument and reduces parasite’s glucose intake - leads to death of parasites.
Describe Niclosamide:
Highly effective against most tapeworms in dogs and cats, except for Dipylidium caninum and Echinococcus granulosus.
In ruminants efficacy against Moniezia spp., horses against Anoplocephala spp.
Used as suspension in ruminants and tablets in dogs and cats.
Mode of action: interferes with parasite’s glucose absorption - leads to death of parasites.
Describe Praziquantel (Isoquinolones class):
highly effective against cestodes of all species!
Also effective against most trematodes.
Used: tablets, paste, suspension for oral administration, solution for SC and IM inject.
Mode of action: induces paralytic muscle contraction and disrupts metabolic process of parasites.
Cestodes of Public Health Importance (5)
Taenia saginata
Taenia solium
Diphyllobothrium spp.
Echinococcus granulosus
Echinococcus multilocularis
