CYCLOPHYLLIDIAN TAPE WORMS PART 1 Flashcards
What about cestodes?
Intestinal zoonotic parasite
* Adult worm lives in human intestine
* Larval form (Cysticercus cellulose) in pigs
* Most common in Latin America, Africa and
India
* 400000 people have symptomatic
neurocysticercosis in Latin America
Differentiate between cyclophyllidia and pseudophyllidia cestodes
①Cyclophyllidia = suckers are cup-shaped
⓶Pseudophyllidia = suckers are shallow, bothria mostly aquatic intermediate hosts
What are the other names of Taenia solium?
=pork tapeworm
= taeniasis solium
= armed tapeworm of man
Describe the morphology of T. solium
- 2–7 meters, 1000 proglottids
- attached by scolex to mucosa strobila folded in lumen
- Region of strobilization at neck
- Immature proglottids broader
than they are long, mature one
almost square.
①SCOLEX/ HEAD
*Bears 4cup-like suckers
⓶UTERUS
*Branching may or may not be present
③UTERINE POLE
*Absent
④COMMON GENITAL POLE
*Lateral
⑤EGGS
*Not operculated; do not give rise to ciliated larvae. *Thick shelled Eggs of Taenia
made up of truncated prisms cemented together. 40000 eggs and not motile
*Shed embryonated, with embryo – Onchosphere = hooked ball with 3prs hooks
* eggs escape from uterus, can survive in soil for many weeks.
How is T. solium transmitted?
①Taeniasis: Man eats undercooked or raw
pork. Gets infected with adult worms
⓶Cysticercosis: Human infections with larval forms
a. Ingestion of eggs in food
b. External autoinfection
c. Internal autoinfection=occurs when a
gravid proglottid is transported back
to the stomach through reverse
peristalsis
Describe the life cycle of Taenia solium and T. saginata
*Man is the definitive host.
①The gravid segments are very active
and escape through the anus
⓶releasing large numbers of eggs in the perianal region or on the ground, where they can survive for long long periods. Faecal egg loads are, therefore, relatively light.
③When ingested by pigs (T. solium) or cattle (T. saginata),
④the eggs hatch, each releasing larval form ,
⑤the oncosphere which migrates through the intestinal wall and blood vessels to reach striated muscle within which it
⑥encysts, forming cysticerci.
⑦When inadequately cooked meat containing the cysts is eaten by man,
⑧the oncospheres excyst, settle in the small intestine and ⑨develop there into adult cestodes over the next three months or so.
⊛The segments of T. solium are somewhat less active than those of the beef tapeworm
but its eggs,
⑩if released in the upper intestine, can invade the host(autoinfection), setting up the potentially dangerous larval infection
known as cysticercosis in muscle or any other site.
Mention the infective and diagnostic stages of T. solium
Infective stage= Embryonated eggs, cysticerci
Diagnostic stage= Eggs or gravid proglottidis
Describe the Pathogenesis of Taeniasis
*Adult worms-scolex attaches to
mucosa
a. Asymptomatic in most
b. May cause abdominal discomfort, hunger
pangs, diarrhoea, nausea, indigestion
alternating with constipation
c. Migrating proglottids from anus
embarrassment or gravid proglottids in
faeces (40000 eggs)
Describe the pathogenesis Cysticercosis
Invasion by Larvae= Nodules in the eyes, muscles, brain
①Cysticercosis cellulosae: fibrotic capsule in muscle, cellular infiltration, necrosis,
calcification
* in Brain – (causes neurocysticercosis)
cysts in Subarachnoids, cranium, fatal if cyst dies, burns, epileptiform seizures due to heavy primary invasion of the brain
⓶Ocular Cysticercosis
-subretinal, subchoroidal
-intravitreous or in anterior chamber
-lodge in eyelid, under conjunctiva
-iritis, retinitis, inflammation
③Cysticercus racemosus:
Proliferating type, no scolex
-grape-like mass with stalks
or channels at base of brain,
may extend to spinal cord
List the Symptoms of Cerebral Cysticercosis
-disoriented behaviour
-transient paresis
-disequillibrium,
-meningoencephalitis
-failing vision
-CSF oesinophilia
How do you diagnose T. solium?
①Taeniasis: Direct faecal examination, Brine floatation/ Formol ether Concentration
techniques, Cellophane tape techniques
(Eggs in faeces, proglottids (7-13 branches of uterus). Evacuated worm – armed
rostellum)
⓶Cysticercosis – excision of larva
cysticercosis of muscle or SubQ, suggest
brain involvement
-X-ray – calcified, CT, MRI
- CT scan of brain
-cerebral Cysticercosis
-history of intestinal Taeniasis helpful.
③Ocular Cysticercosis
- whitish grayish mass in
anterior chamber
- movement of scolex is pathognomonic
Treatment of T. Solium?
①Adults or Taeniasis
‣Praziquantel 10mg/kg single dose or Niclosamide, or Mebendazole expulsion of worms prevents
autoinfection and Cysticercosis
⓶Treatment for Cysticercus
a)Excision, removal of cyst, while it is
living reduces damage to organ
b)Praziquantel destroys cysticercus in brain +corticosteroids
③For cutaneous infections: Metrifonate
④Radioactive Iodine – Ab Targeted therapy
What are the common names of Taenia saginata?
- Beef tapeworm infection
- Taeniasis saginata
- “unarmed tapeworm”
Describe the Morphology of T. saginata
*Scolex with 4 hemispherical suckers , 4 angles, No rostellum, no hooks
Scolex imbedded in mucosa
*15m or more under favourable (25m) *1000- 2000 proglottids
*mature Proglottids broader than they are long
*Gravid proglottids narrower than longer 20 x5mm
*Detached gravid proglottids are actively motile
*Bilateral genital pores
- 15-20 main lateral branches of uterus
- Eggs – indistinguishable from T. Solium
Describe the pathogenesis of T. saginata
Prepatent period 10-12 weeks
1. Intestinal disturbances, weight loss, intestinal obstruction, Proglottids lodge in appendix
2. Diarrhea, hunger pangs, discomfort,
embarrassment at crawling proglottids
3. Causes cycticercus bovis in cattle, reindeer
4. Eggs not infective to man hence Taenia
saginata does not cause cysticercosis in
man
