Parasitology Exam 3 - part 3 Cestoda

Class Cestoidea

tapeworms

Where are class cestoidea found?

in digestive tract of hosts

What is cestoidea in mammals?

mostly carnivorous and omnivorous

Strobila

Chain of proglottids, linear series of sets of reproductive organs of both sexes

Polyzoic species

having numerous proglottids

Monozoic species

only have one set of geneitalia

strobilation

new immature proglottids continuously produced behind scolex

What is a continuous process like an assembly line?

strobilation

Copulation

the act of mating, as each move toward posterior and matures

gravid

once proglottid contains mature eggs or embryos

What happens when the end of the strobila detaches or breaks up.

the proglottids or eggs pass out of host with feces

Scolex

equipped with hold fast organs

Acatabula

cup shapped scolex usually 4

Bothridia

usually are in groups of four; are quite muscular, projecting sharply from the scolex; and can have highly mobile, leaflike margins

Bothria

shallow sucking grooves on some cestodes, shallow pits and grooves normally two of them

What does the scolex do?

Aids in attachment to lining of host gut

What part of the tapeworm contains stem cells?

the neck

What is highly variable and often diagnostic to species.

the scolex

What is lacking in a tapeworm?

a digestive system

What is the tegument of tapeworms covered in?

microtriches

microtriches

hairlike surface structures that absorb nutrients in tapeworms

fingerlike extensions that dramatically increases surface area

microtriches

Muscular system of tapeworms?

scolex with complex musculature, highly mobile, proglottids often musculated as well

Nervous system of tapeworms

- Ganglia in scolex
- Many sensory structures on scolex
- Lateral nerves through strobila

What can be found in the scolex of the tapeworm?

ganglia and many sensory structures

What can be found in the strobila of tapeworms?

lateral nerves through out

Mostly all tapeworms are what

monoeceous

The structures and arrangement of organs within proglottids are useful for what?

identification

The female reproductive system contains a structure in which eggs exit.

genital pore

Tapeworms of the class cestiodea have how many hosts?

two or three hosts

various stages and forms of tapeworms

eggs --> oncosphere --> metacestode

Metacestodes

Able to crawl, undergo metamorphosis through various forms, eventually form cysticercoid

What must be ingested by definitive host to mature?

cysticercoid

Cysticercoid

The larval stage of some tapeworms; a small, bladderlike structure containing little or no fluid in which the scolex is enclosed

monozoic species

found mostly in fish

polyzoic species require how many hosts?

two, forms cysticercoid in intermediate host, consumed by definitive host, a few requires three species

Diphyllobothrium species

broad fish tapeworms

Diphyllobothrium latum may reach how much in length

30 feet in length

D. dendriticum is about how long?

1 meter

What does the scolex of Diphyllobothrium species look like?

finger shaped

What do the proglottids of Diphyllobothrium species look like?

gravid proglottids much broader than long, several released at a time as short chain

How any eggs are released from Diphyllobothrium species?

releases up to 1 million eggs daily

Life cycle of Diphyllobothrium species

Egg hatches, coracidium is eaten by copepod, fish eats copepod, mammal eats raw fish, adult develops in intestine

Pathogenesis of Diphyllobothrium species

may cause diarrhea, nausea, or weakness, could also cause pernicious anemia

Why is pernicious anemia sometimes caused by Diphyllobothrium species?

The worm absorbs large amounts of Vitamin B12

Diagnosis and treatment of Diphyllobothrium species.

- Eggs or proglottids in feces
- Praziquantel used most often

Epidemiology of Diphyllobothrium species.

- Practice of eating raw or
undercooked freshwater fish
- Sewage disposal

Sparganosis

Plerocercoid in human tissue from accidental infection with procercoid of several species of Cestodes. can remain in intestine when become adults

Why can sparganosis be dangerous?

Juveniles may multiply by budding
• May feed on vital organs

Order Caryophyllidea

lacking proglottids (monozoic), adults can be found in intestines of freshwater fishes

Taenia pisiformis

dog tapeworm

Which tapeworm is not found in humans?

Taenia pisiformis

What is less than 1 foot in length

Taenia pisiformis

scolex has small hooks

taenia pisiformis

Taenia saginata

beef tapeworm

How long can taenia saginata reach

May reach 60 feet in length, but most are 6 to 10 feet
long
• Adults often made up of over 2,000 proglottids

Scolex has 4 suckers and no hooks

T saginata

Life cycle of Taenia saginata

Human = definitive host
cow = intermediate host
matures in small intestine
-Eaten by human in rare beef
-shelled larva is in feces
-cattle eat grass which contain proglottids (with fertilized eggs)
-each hatch into larva and bore through cow's intestines into bloodstream
-larva burrow into cow's muscle and form cysts

Pathogenesis of Taenia saginata

Usually mild symptoms or none
• Dizziness, abdominal pain, diarrhea, headache, sensitivity,
nausea
• Rarely; delerium, intestinal obstruction, or allergic reactions

Diagnosis and treatment of Taenia saginata

Usually a scolex or gravid proglottid needed for
identification
- ELISA also useful
- Treatment with praziquantel most common
Taenia saginata

What can cysticerci in beef be called?

measly beef

At what temp can cysticerci be killed at?

at >56 C or at <-5 C for more than one week

Where is Taenia saginata found?

• Beef commonly eaten
• Sanitation poor

Taenia asiatica

uses pigs

Taenia solium

pork tapeworm

Proglottids virtually identical to
those of T. saginata
• Fewer uterine branches
• Fewer testes

Taenia Solium

Scolex has distinct hooks on rostellum

Taenia solium

Life cycle of Teania solium

- Life cycle like T. saginata, but pigs and bears
primary intermediate hosts
- Obtained by eating raw or poorly cooked pork or
bear
- Contamination from raw pork

Cysticercosis

infection with the larval stage by ingesting eggs

What happens if a human consumes the eggs of Taenia solium?

Happens easily if already infected with
adults
• Cysticerci may form in all organs
- Especially eyes and brain
• Cysts mostly about 1 cm in diameter

Echinococcus granulosus

- Small dog tapeworm
- Occurs in domestic and wild canids
- Very dangerous to humans
• Not common in humans, but not rare

What only has three proglottids at a time?

Echinococcus granulosus

Lenght of Echinococcus granulosus

adults tiny, 3 to 6 mm in lenght

What does Echinococcus granulosus cause?

cystic echinococcosis (hydatid cysts) often in the liver and lungs

Life cycle of Echinococcus granulosus

Hoofed mammals intermediate hosts
- Dogs obtain by eating intermediate hosts

Epidemiology of Echinococcus granulosus

- Common where dogs feed on parts of butcheredlivestock - especially sheep- Many other routes as well

hydatid cysts

Echinococcus granulosus, symptoms may take years to develop and symptoms are dependent of location of cyst

What happens if the cysts of echinococcus granulosus ruptures?

Sudden death due to anaphalaxis

Echinococcus multilocularis

Eurasia, Northern North America
• Occurs in foxes, dogs, coyotes, cats
• Cysts unique
- Infiltrates tissues, appears cancer-
like

Echinococcus vogeli and E. oligarthrus

Mostly in New World tropics, adults in birds and mammals

Hymenolepis nana

- Dwarf tapeworm
- Very common in humans, especially children
- Human infection rate can be high
• Over 97% in Moscow

- Adults tiny - <40 mm in length- Scolex has hooks

Hymenolepis nana

Life cycle of Hymenolepis nana

- Unique, does not always need
intermediate host
- Eggs consumed by grain beetle,
flea larva, human, or rat

When in an insect where would cysticercoids be from hymenolepis nana?

hemocoel

If in a mammal where are cysticercoids found?

found in lymphatics of intestinal villi

Pathogenesis of Hymanolepis nana?

Symptoms generally lacking unless infection heavy
- If heavy, symptoms much as in T. saginata
- Treatment with praziquantel highly effective

Hymenolepis diminuta

- Common in rats, occasionally
humans
- Adults to nearly 1 meter in length
- Scolex lacks hooks
- Three testes per proglottid
- Eggs lack polar filaments - differ
from those of H. nana

Dipylidium caninum

dog tapeworm - Two-pored tapeworm- Common in dogs and cats worldwide• Sometimes in humans - mostly children

Each proglottid has two sets of genitalia, two pores - one on each side

Dipylidium caninum

Scolex with retractable rostellum, rostellum with hammer-shaped spines.

Dipylididum caninum

Life cycle of Dipylidium caninum

-Adult tapeworm sheds proglottids through hosts feces
-Eggs are consumed by flea larva
-Fleas mature and infect a host
-Host eats the flea and consumes eggs
-Egg hatch and larvae migrates to small intestines to mature into tapeworm

Moniezia species

Hoofed mammals usually definitive
hosts
- Especially cattle and sheep
• Arthropods intermediate hosts -
especially mites
• May exceed 10 feet in length

Moniezia species

• Mature and gravid proglottids much
wider than long
• Two sets of genitalia - one on each
side

Mesocestoides spp.

May occur in cats and dogs and occasionally in humans

Scolex with 4 suckers, no hooks

Mesocestoides species

Unique group because at least one species -- asexual reproduction by longitudinal fission of scolex

Mesocestoides species

Life cycle of mesocestoides species

intermediate hosts unknown, definitive hosts include birds, mammals, and some reptiles --- all carnivores

Order Proteocephalata

- Adults in freshwater fishes, amphibians,
and reptiles
- Intermediate hosts - copepods
- May have paratenic hosts

Order Tetraphyllidea

Often have bizarre scolex
forms
- Adults in sharks, rays, and
allies
- Intermediate and paratenic
hosts poorly known
• Likely fishes, molluscs, and
crustaceans

Why is the scolices of Order Trypanorchyncha unique?

four bothridia, four eversible tentacles often covered with hooks and spines