Diphyllobothrium latum: (Broad fish tapeworm).
Scolex does not have suckers. Has two sucking grooves
instead. No hooks.
Proglottids are broad and gravid uterusin the form of a
Eggs oval / elleptical, with a large operculum at one end
and with a small node at the other end.
Have two intermediate hosts: copepod crustacea (first)
and Fresh water fish (second).
The plerocercoid larva attaches to the mucosal lining of the ileum or
at times jujenum with both bothria (sucking grooves). Develop into
Gravid proglottids release fertilized eggs through the genital pore
and pass out in the stools.
When the eggs are deposited / Come in contact with fresh water,
the eggs lie dormant (8-12 days) to form Coracidia –operculum
opened – larva begins to swim – eaten by copepods – develops
from coracidia to procercoid larva in the hemocoel of the copepodcopepod eaten by fish – procercoid larva penetrates the intestines
and migrates to the musculature- humans infected on eating the fis
raw or uncooked containing the plerocercoid larva – attaches to the
small intestine of humans.
and Clinical findings:
of adult worms generally
Gastrointestinal manifestations such as nausea,
vomitting, diarrhea, abdominal pain, weight loss
may be seen.
In some individuals, significant Vitamin B12
deficiency caused may lead to megaloblastic
anemia. Vitamin B12 preferred and consumed
by the worm.
findings, Treatment and prevention:
of the typical yellowishbrown, ellipsoidal eggs with operculum or
characteristic broad proglottids in the stool
sample of the infected individual.
Treatment of choice: Praziquantel.
Prevention: Adequate cooking and proper
disposal of human feces.
Dipylidiasis caninum:(Double-pored Dog tapeworm)
Adult worm is small, measuring only 10-50 cms.
Scolex has 4 suckers and about 60 thorn like hooks
arranged 1-7 lines around retractile rostellum.
Proglottids have two sets of reproductive organs and are
trapezoidal near the neck and barrel-shaped towards the
Eggs are spherical.
Definitive host: Dogs, cats etc…
Intermediate hosts: Animal fleas.
Adult worm parasitizes the small intestines of dogs, cats and other
wild animals as well.
Gravid proglottids come out through feces - release eggs/ egg balls
by contractile motion- ingested by the flea larva- grow into adult fleahatch in the digestive canal- develop into oncospheres – develop
into cysticercoids in the flea.
Infected insect swallowed by the dog, cat and cysticercoids grown
into adult worms in 20 days time in small intestine of the dogs.
Humans are accidental hosts – spread especially to children by
licking or touching dog infected with flea containing cysticercoids.
and clinical symptoms:
worms parasitic in the middle and posterior
part of the small intestine.
Deeply insert the rostellum with many hooks into
the mucosa and damage the tissue.
Consequently, bleeding may result if the
numbers are large with gastrointestinal
Diarrhea and pruritis ani may occur.
diagnosis, Treatment and Prevention:
by observing gravid proglottid
crawling out of the anus, egg balls or free eggs.
Demonstrating typical barrel shaped proglottids.
of choice: Praziquantel, Niclosamide.
Prevention: Deworming of dogs/cats, avoid
contact of children with infected pets.
E.ganulosus is one of the smallest tapeworm.
Made up of only three proglottids. The first contains
immature genital organs, the second has fully developed
male and female reproductive organs and the third
consists principally of a median uterus and lateral
branches filled with eggs.
The scolex bears a prominent rostellum, a double crown
of 24-40 large and small hooklets, and 4 oval suckers.
The eggs appear like Taenia worm eggs with radial
striations containing a hexacanth, six hooked embryo.
The larva of E.granulosus in the intermediate host is
known as a Hydatid cyst.
cyst is filled with fluid called hydratid fluid
which contains proteins, lecithin and other
nutrition besides some enzymes.
From the inner germinal membrane, masses of
cells grow into the cavity of the cyst. They
generate many protoscoleces withinand outside
the brood capsules, both generated from the
inner germinal layer.
Besides containing brood capsulesand
protoscolesces, the cyst can contain daughter
cysts each being a miniature cyst with its own
brood capsules and protoscolesces.
free protoscolesces, brood
capsules, daughter cysts and the
amorphous material are together known
as the Hydratid sand.
Some cysts may be infertile without any
protoscolesces or brood capsules
The adult E.granulosus inhabits small intestine of dogs and other canines –
eggs discharged from ruptured proglottids – pass out through feces – eggs
ingested by cattle, sheep, hogs, horses etc.. (intermediate hosts) – Eggs
hatch in the duodenum –embryos penetrate the intestinal mucosa and
carried by portal blood to the liver – many remain there – the remaining
traverse the liver and carried to the lungs where they reside – a few pass
through the pulmonary capillaries and carried to the brain, heart, bones,
kidneys and other tissues where most of them are phagocytosed _ some
survive, undergo central vesiculation and form a cyst wall composed of an
external laminated cuticle and a inner germinal membrane.
The cyst fills with fluid – expands and act as a space occupying lesion,
putting pressure on the adjacent tissue. The outer layer is the thick, fibrous
tissue produced by the host.
When hydatid liver / organ eaten by the definitive host such as dogs, the
cycle is completed, where each of the individual protoscolesces develop into
Pathogenesis and clinical manifestations:
Local compression and excitation: Cyst acts as a space occupying
lesion- puts pressure and damages adjacent tissue by mechanical
and immuno-pathologic means.
The cyst fluid contains parasite antigens which can sensitize the
host causing an allergic reaction like pruritis and uticaria.
If the cyst ruptures spontaneously or trauma or surgical removal, a
potentially life threatening Anaphylactic shock can result in fatality.
Secondary hydatid cysts or inflammation due to the ruptured cyst
may result and become the cause of dissemination.
The parasite toxin may also manifest into gastrointestinal symptoms
such as anorexia, maldevelopment, and cachexia with weight loss.
in the liver may cause hepatomegaly,
obstructive jaundice, with intrabiliary extrusion of
calcified cysts mimicking acute cholecystitis.
Cysts in the lungs may develop into cough,
emphysema, hemoptysis and chest pain.
Cysts in the brain may cause neurological
symptoms, cardiac lesions can result into
conduction disturbances, ventricular rupture and
embolic metastases.Circulating antigen-antibody
complexes may result in glomerulonephritis.
diagnosis, treatment and prevention:
of brood capsules containing
protoscolesces and Indirect hemagglutination
tests (positive in 90% of liver lesions).
Treatment of choice: Albendazole with or without
surgical removal of cyst (care to be taken that
protoscolesces are not released-killed by
injecting hypertonic saline).
Prevention by not feeding remains of infected
slaughtered sheep to dogs.
features same as E.granulosus.
Definitive host mainly foxes. Intermediate
hosts are rodents. Humans ingesting food
contaminated with fox feces are accidental
and clinical manifestations:
primary focus is the liver and the larva form
multiloculated cysts with few protoscolesces as
there is no outer fibrous capsule formrmed, the
cysts are free to proliferate, producing a honeycomb effect of small vesicles.
These multilocular cysts slowly but progressively
invade and destroy the affected organs and
symptoms can begin with epigastric
pain, hepatomegaly, hepatic mass,
obstructive jaundice, hepatic failure, and
may also lead to metastasis to the lung,
Prognosis is thus poor.
diagnosis, treatment, and prevention:
of brood capsules,
protoscolesces, Indirect hemagglutination tests.
Treatment of choice : Albendazole in some
Prevention: Elimination of mice and voles and
avoid potentially contaminated flesh of animals.