Introduction to Platy Helm Int Hes Tapeworms)

8/8/2019 Introduction to Platy Helm Int Hes Tapeworms)

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Major Attributes:

Endoparasitic.

Acoelomates Body is covered by tegument.

Anterior end is a scolex.

Body segments called proglottids. Hermaphroditic.


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General Structure of Tapeworm


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Cestoidea

y Some species can reach lengths of up to

thirty meters. (Hexagonoporus from whale)

y Life cycles require one, two or three

intermediate hosts.

y Many life cycles involve man and domestic

animals.


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Tapeworm Structure Scolex - Attachment organ

Zone of Proliferation - Undifferentiated areabehind the scolex (neck region)

Strobilia - Chain ofsegments (proglottids)

y I

mmature proglottids - developing reproductivey Mature proglottids: mature reproductive organs.

y Gravid proglottids: contain eggs in the uterus.


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Scolex


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Taenia sp. Scolex


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Four Types of Proglottids

As proglottids are formed, they are pushed

posteriorly. There are 4 regions.

a. Zone of proliferation

b. Zone of immature proglottids

c. Zone of mature proglottids - area with

sexually mature organs Gravid zone - area where proglottids contain

eggs.


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Tapeworm Strobila Linear series of sets of reproductive organs

(proglottids).

Each mature proglottid contains male and

female reproductive organs.

New proglottids produced by strobilization

which is a budding that occurs from theneck region (the zone of proliferation).


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Egg Release from Proglottids Apolysis - entire proglottid containing eggs

is released or disintegrates releasing eggs.

b. Anapolysis or Pseudopolysis-

proglottids remains attached eggs are

released through some uterine pore or tear

in the gravid proglottid. c.Hyperapolysis - immature proglottid

released and matures within the host.


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Tapeworm Scolex Scolex

Most tapeworms have some type of

attachment organ located at the anterior end.

There are many adaptations including suckers,

hooks, grooves and some tapeworms lack a

scolex altogether. See page 301 for differenttypes of scolices


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Types of Tapeworm Scolices Pseudoscolex is a distortion of the anterior

end of the strobila.

Acetabula - suckers is most common form

Bothria - take the form of slits or grooves

as in Diphyllobothrium latum

Bothridia - often leaf-like muscular

projections, usually in groups of four.


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Hymenolepsis diminuta scolex


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Scolex


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Rostellar hooks


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Trypanorhyncha scolex


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Tapeworm Tegument

(integument) Adult tapeworms live in the digestive tract of

host lack a digestive tract. The result is that the

adult tapeworm must absorb all nutrients it getsthrough the integument.

The integument is a highly specialized tissue

with high metabolic activity covered by minute

projections called microtriches (similar tomicrovilli). These increase surface area

(increase absorption efficiency).


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Tapeworm Tegument

(integument) Glycocalyx is a layer of carbohydrate

containing macromolecules that coats the

integument. It may enhance absorption ofcertain substances and at the same time

inhibit activity of host enzymes that would

digest the worm.


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Reproduction Tapeworms are hermaphroditic

Each mature proglottid has both male and

female reproductive organs.

Cross fertilization gives genetic variability

Protandry or androgyny - the testis matures

before the ovary.

Protogyny or gynandy - eggs develop before

the sperm.


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HowF

ertilization Occurs In some cases fertilization occurs between

the male and female gonads found in the

same proglottid or in different proglottids ofthe same worm. (self-fertilization)

In other cases, fertilization occurs between

different worms in the digestive tract of thehost.

A few cestodes are dioecious


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Tapeworms All tapeworms are parasites

Most parasitize wild animals few important

parasites of men.

Only orders Pseudophyllidea and other

Cyclophyllidea contain tapeworms of

importance to humans or parasites of man.


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Order Pseudophyllidea: Bothria with longitudinal grooves form

scolex


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Order Pseudophyllidea: Contains many small species but also the

largest species (Hexagonoporus from

whale) commonly reaches 30 meters andthe record is one 200 ft long

These usually have some crustacean as first

intermediate host and second intermediatehost is often a Fish


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Diphyllobothrium latum)

broad fish tapeworm -

common in fish eating carnivores of

northern Europe

low level of host specificity or maybe

several very similar species.

Some areas 100% of population infected

pg. 346 2nd column


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Diphyllobothrium latum)

Morphology: -

a. 30 ft long - shed 1 million eggs/day

Scolex finger shaped with 2 bothria

Proglottids wider than long (broad tapeworms


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Stages inL

ifeC

ycle Eggs passed in feces - in water develop

hatch into coracidium.

Crustacean (copepod) ingests coracidium.

Coracidium loses cilia - reaches the

hemocoel and develops into procercoid.

Crustacean eaten by fish - develops into

pleurocercoid (small fish eat crustacean,

larger fish eat smaller fish)


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Stages inL

ifeC

ycle Definitive host becomes infected when it

ingests infected fish.

The pleurocercoid develops into adult to

begin egg production in 1-2 weeks


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Epidemiology People become infected ingesting

improperly cooked fish.

Improper disposal of sewage into water -

greater infection rate.

Exporting of raw fish - improper cooking.


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Pathology Phyllobothriasis

Many cases asymptomatic

Pernicious anemia caused by tremendous

absorption of Vitamin B12 by worm -

Vitamin B12 needed to make RBC.


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Pathology Sparganosis:-

larval forms found in humans

results of procercoids being ingested.

pleurocercoids can migrate from gut and

develop in organs of humans.

use of using raw fish or amphibian as a poulticefor medical treatment - pleurocercoid leaves

fish or frog - enters skin of patient - eyes,

vagina, pg. 329 Fig 21.9.


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OrderC

yclophyllidea Compact single vitelline gland

Scolex with 4 suckers

Genital pore generally lateral

Contains most tapeworms of birds and

mammals.


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F

amily Taeniidae Largest cyclophyllideans of man - with

exception ofGenus Echinococcus.

Contains most important medically to man

Most species contain a rostellum which is

non-retractable armed in most species - not

in all

Testis are numerous and ovary is bilobate

mass near posterior margin of proglottid.


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MostI

mportant Species Taenia solium

Taeniarhynchus saginatus

Echinococcus granulosus

Echinococcus multilocularis


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T

aenia solium -Pork Tapeworm Adult found in digestive tract of man.

Potentially dangerous because man can

become infected with larval stages.

Intermediate hosts pigs ingest oncospheres

which develop into cysticerci in tissues.

Man becomes infected ingesting raw meat.

Strobila commonly 6-10 feet long lengths of

over 30 feet reported


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T

aenia solium - Morphology Scolex - 4 suckers rostellum armed with 22-

32 hooks.

Gravid proglottis longer than wide - medial

stem with 7 to 13 lateral branches as

compared to 15-20 lateral branches in

Taeniarhynchus saginatus) See figure 21-15 pg. 332.

Can not distinguish different Taenia eggs


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T

aenia solium Biology Gravid proglottids passed in feces - flabby

and inactive (unlike Taeniarhynchus

saginatus.

Eggs when ingested by pigs develop - into

oncospheres and to cysticerci in muscles

and other organs called measly pork. Person infected eating measly pork.

Worm may live for 25 years.


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T

aenia solium andsaginata Gravid proglottids ofTaenia solium has

7 - 13 primary lateral branches.

T. saginatus has 15 - 20 branches oneach side.


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T

aenia solium andT

. saginatus


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C

ysticercosis in humans Man must ingest embryonated egg (fecal

contamination of food, hands, etc.

or

Gravid proglottid migrates or is moved by

reverse peristalsis from intestine to

stomach.

Reenters intestine where eggs hatch - may

lead to massive infection.


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Cysticercosis in humans

Oncophere enters lymphatic and blood

vessels.

May develop in any organ most common it

develops in the muscles.

In eye usually results in irreparable damage.

In Brain may result in paralysis, obstructivehydrocephalus, epilepsy - sometimes death.

Inflammatory response (allergic) may be fatal.


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Cysticercosis in humans

Oncophere enters lymphatic and blood

vessels.

May develop in any organ most common it

develops in the muscles.

In eye usually results in irreparable damage.

In Brain may result in paralysis, obstructivehydrocephalus, epilepsy - sometimes death.

Inflammatory response (allergic) may be fatal.


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Taenia solium cysterci in brain


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Prevention:

Properly cook pork.

Proper disposal of human feces - and

personal hygiene

If adult worms in man - Need to treat

humans to eliminate worms to prevent auto

infection of cysticerci.

Caution in using night soil on gardens


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Taeniahynchus saginatus

Most common taeniid of humans.

Occurs in all countries where beef is eaten.

Morphology Scolex cuboidal up to 2mm in diameter - lacks

hooks

Long species - strobila up to 75 ft commonly 10- 15 feet.

gravid proglottid with 15 - 20 lateral branches


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Biology ofTaenia saginatus

Gravid proglottids exit in feces or migrateout anal opening - very active in contrast to

Taenia solium. Eggs are fully embryonated and infective to

intermediate host. They may survive manyweeks.

Cattle becomes infected upon ingestion ofembryonated eggs.


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Biology ofTaenia saginatus

Egg hatches hexacanth penetrates mucosa -intestinal venules - throughout body. Often

enters muscle tissue. Forms cysticercus, known as cysticercosis

bovis and meat is called measly beef.

person becomes infected by eatingimproperly cooked measly beef.

In man worm develops into mature adults.


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Pathology

Reactions to the absorption of excretions ofworms - host reaction.

Blockage of digestive tract in high infectionnumbers

Abdominal pain, headache, diarrhea,dizziness and others.

Prevention includes Proper sanitation andProperly cooking beef.


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Echinococcus granulosus

Genus Echinococcus contains smallest

tapeworms in family Taeniidae.

Juvenile forms capable of developing in

humans resulting in hydatidosis.

Echinococcus granulosis - has carnivores,

especially dogs and other canines asdefinitive hosts.


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Morphology

Adult 3-6mm long when mature

Consists of Scolex - short neck usually 3

proglottids (immature, mature, gravid)


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Hydatid cysts


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Hydatid Cysts


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Hydatid sand


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Mature protoscolex


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Echinococcus granulosis

hydatid cyst

Internal budding produces daughter cysts

and brood capsules. Daughter scolices and brood capsules may

break off sink to the bottom called Hydatid

sand


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Epidemiology

Sylvatic cycle - Wolf and some herbivore

(Moose).

Urban cycle - domesticated dogs - man

(sheep, cattle and other herbivores).

Tribes in Kenya - relish dog intestine - see

pg. 339 - first column


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Pathology

May not become evident for many years.

Pathology depends on location of hydatid

cyst in host if vital organ severe damage - maybe death

- brain, heart, liver.

If non-restrictive tissues, hydatid may reachsize containing 15 quarts of fluid. Should it

upture, anaphylactic shock and death.


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Prevention

Care not to ingest eggs from dog - Proper

hand washing - children most likely to get

infected

Treatment of dogs.


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Echinococcus multilocularis

Known from Europe, Asia, North America.

Primarily associated with trappers and

handlers of shed teams.

Produces alveolar or multilocular hydatid

cysts - infiltrates into surrounding host

tissue like cancer.


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Prevention

Prevented by avoiding dogs (foxes) etc in

endemic regions, carefully washing

strawberries, cranberries that may becontaminated with dog feces and regular

worming of dogs liable to infection.


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Vampirolepis nana

(Hymenolepsis nana)

The dwarf tapeworm - most common

tapeworm in man

Cosmopolitan

97% of people in Moscow, 1% of people inSoutheast U.S.


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Vampirolepis nana

(Hymenolepsis nana) Intermediate host is optional. It can have a

direct or an indirect life cycle

Direct life cycle eggs ingested, hatch induodenum, develop into cysticercoid and adult.

Indirect life cycle involves grain beetle.Cysticercoid develops in beetle and man

becomes infected by ingesting grain beetle.Common in areas where grain stored and

people dependent upon it on a daily basis.


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Prevention

Proper sanitation

Properly cook grains

Documents

Introduction to Platy Helm Int Hes Tapeworms)