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.))