CYCLOPHYLLIDIAN TAPE WORMS PART 2 Flashcards
What are the common names of Echinococcus granulosus?
-Dog tapeworm
-Hydatid disease
-Hydatid worm
-Unilocular echinoccocosis
What is the habit of Echinococcus granulosus?
- Adult worms in small intestine of dog and
other canine animals - Dog is definitive host
- Larval form seen in man & other
intermediate hosts (sheep, goat, cattle, pig & horse)
Describe the morphology of Echinococcus granulosus
Morphology:
①Adult worm 3- 6mm in length
* Scolex-Armed with 4 suckers, 28-50 hooks
* Neck- short and thick
* Strobila- three segments
a. 1 immature proglottid
b. 1 mature gravid proglottids
c. Terminal gravid proglottids broadest and largest
uterus loosely twisted coil – relatively few eggs worm longevity in dogs 5-29 months
⓶Eggs: Indistinguishable from those of
Taenia
③Larval form
* Found within the hydatid cyst which
develops in the intermediate host (12cm with daughter cysts 7cm in diameter)
The Cyst: Intrinsic cyst wall differentiated into
1. Out friable, milk-opaque, non-nucleated laminated layer
- Inner nucleated germinal layer generally parasite cells budding into cystic cavity, vacuolated and on stalks= Brood capsules containing protoscoleces, invaginated, mature fully, and become infective.
Describe the life cycle of Echinococcus granulosus
①The adult tapeworm inhabits the small intestine of dogs , eggs in the faeces (II)Eggs ingested by herbivores
⓶ Hatch in the duodenum, the hooked embryos entering the circulation where they are carried to various sites to develop into cysts
③Dogs become infected when they eat the cysts contained in contaminated offal.
④Humans are infected if they accidentally ingest
eggs from infected dogs.
⊛The liver is the commonest site for the cysts.
⊛NINE distinct genotypes within the
E. granulosusus complex have been
identified by molecular based procedures. Their full epidemiological importance not yet been defined
Describe the Pathogenesis of Echinococcus granulosus
①Mechanical – Abdominal masses impair functions of vital organs, or grow large, become physical burden and burst- Anaphylactic shock, bones break.
⓶Always serious disease Unilocular
cyst, position 5-20 years later symptoms
-incomplete insulation
-allergic, anaphylactic
-bronchial or billary abscess
-arterial embolism – metastasis
-brain, orbital, capillary, heart valve
- Liver and pulmonary commonest
③Osseous – erosion, multiple fracture and
crumbling of bone :
* Sterile cysts no brood capsules caused by
bacterial infection or calcification acephalocysts brood capsules that do not produce protoscoleces 5-20cm, 2L fluid
*Osseous hydatid – confinement in bone, laminated layer poorly developed organism grows along the bone canal as a naked protoplasm, erroding osseous tissue
④Lung hydatid – intracapsular, prone to
spontaneous rapture – rapid recovery or
Asphyxiation
⑤Calcification
⑥Secondary infected
How is the Prognosis of hydatid cyst caused by E. granulosus
*Fair in unilocular, operable site
*Spillage into operative cavity – critical centres-Grave
*Marsupialization prevents spillage and
metastasis
Echinococcus multilocularis
=Alveolar hyadatid Disease
=Sterile – no protoscoleces, exogenous budding, bare germinal layers progressive invasion of
the organs 90% like an invasive neoplasms
-Resemble carcinoma, matastasie
-Hepatic
*The adult of this species is found in WILD CANINES1, and the usual larval hosts are RODENTS.
*The alveolar cyst in the human liver may mimic hepatic carcinoma, but it is usually only discovered post mortem.
Treatment of E. multiocularis
- Surgical removal – resection
- Mebendazole – works survival in hepatic
hyadatosis – 14.5 yrs. – slow growth
Prevention:
1. Control of dogs and cats/children treat 20-
30 days
What is the epidermiology of Echinococcus tapeworms?
Australia, N. Zealand, Europe,
India, China Absent S. USA, N & S. America,
W. Africa
Enzootic/endemic regions: cattle grazing
countries e.g in New Zealand
0.1% infection rates in dogs
10% infection rates in ewe livers
About Dipylidium caninum:
*The dog tapeworm of dogs and cats
Habitat: intestinal
Describe the morphology of D. caninum
- 10-70cm
- Rhomboidal, small, scolex, armed, rostellum with 7 circlet of spines
- Proglottids: double set of reproductive organs, mature and gravid proglottids shaped like pumpkin seed
- Gravid proglottids filled egg chambers of 8-15 eggs, enclosed in embryonic membrane
- Eggs hyaline brick red, tinge, thin shelled. Delicate hooklets
Life cycle of Dipylidium caninum
(I) The adult cestode in the small intestine
of dogs, cats or wild canids,
(2) Proglottids or clusters of encapsulated eggs passed in feces
(3). Oncospheres hatching from eggs ingested by flea larvae remain undeveloped until the larvae pupate, whereupon they develop into cysticercoids
(5). The cysticercoids undergo a complicated
metamorphosis in the body cavities of the
pupal flea
6) Infected adult fleas (7) and (8, I) pass
into the small intestine of the definitive host
when it accidentally ingests the fleas, there
everting the hooked rostellum to attach to the
gut wall where it will mature into an adult.
Describe the Pathogenesis of Dipylidium caninum
- Slight intestinal disturbance, indigestion,
loss of appetite - Mostly children, proglottid migration from
anus causes anxiety.
Diagnosis: eggs and proglottid identification
Treatment: Niclosamide
Epidemiology: all in children, exposure or
tolerance, Zoonois, cosmopolitan
Hymenolepis nana
*The dwarf tapeworm= Vampirolepis nana
Morphology
=40mm, small scolex armed with 20-30 spines
=Egg – oncosphere enclosed in
=inner membrane, 2polar thickenings, 4-8 polar
filaments
=Oncosphere with 3prs lancet-
shaped hooklets
Life cycle of Vampirolepis nana
(I) Eggs released from mature proglottids in
the upper ileum are passed in the faeces.
(2) If ingested by another person, they hatch to
yield hexacanth oncospheres, which burrow
into the villi of the small intestine. There they
mature into tailless cysticercoids (cercocysts),
which migrate towards the ileum where the
scolices become attached to commence the
formation of leave the villi, move further
down the gut and become attached to other
villi where they mature to adult tapeworms.
proglottids.
(3) Eggs that are ingested by such
insects as fleas, beetles or cockroaches hatch
to form tailed cysticercoids, which remain
unmodified as long as they are within the
insect’s body cavity. If infected insects are
accidentally ingested, the cysticercoids pass
down the intestine to establish themselves in
the ileum of the new vertebrate host. In this
way rodents, as well as humans, may be
infected,
