Parasitology 7: Platyhelminthes

Question 1

You find a spirurid species that you have never seen before. 1 thing that you can say about this parasite?

Answer 1

Parasite is transmitted by an arthropod

Question 2

A dog in you practice needs a blood transfusion. The only compatible donor available presents MF in blood (positive to heartworm). Can you go ahead with the transfusion? Why?

Answer 2

Yes

because MF is NOT the infective stage

Question 3

What are examples of Platyhelminthes?

Answer 3

Tapeworms

Flukes

(FLAT worms)

Question 4

What are the general characteristics tapeworms and flukes?

Answer 4

Flat mostly

Hermaphrodites

Definitive host diagnosis: eggs

AT LEAST 1 INTERMEDIATE HOST

Question 5

Tape worm

segmented?
where are the found?
organs?
host?
pathogenic?

Answer 5

Segmented, often long

Adults in host GI tract, almost always small intestine

Worms have no intestine, absorb nutrients across surface

At least 1 intermediate host

Adults often nonpathogenic but people repelled

Question 6

Adulat tapeworm are ___________ into regions

Answer 6

Divided

Scolex (holdfast)
-sucks and/or hooks
-attaches to gut wall

Neck
-region of cell division, gives rise to proglottids

Proglottids (segments
-segments mature as they travel down the chain
-oldest segments at the posterior end

Question 7

Each segment has at least one set of all reproductive organs of both sexes

Classified as?

Maturation?

Common tapeworms shed gravid _____

Answer 7

Classified as
* Immature
* Mature
* Gravid: contains fully developed eggs

Maturation occurs as moves down the chain
Common tapeworms shed gravid SEGMENTS

Question 8

What is the general term for larval tapeworm?

Answer 8

Metacestode

INFECTIVE STAGE

Question 9

Are the few or many different morphologic types of larval tapeworms?

Answer 9

Many

Question 10

What is the general life cycle of Cestoda?

Answer 10

Intermediate host eats eggs in environment

Definitive host eats intermediate hosts

Question 11

Common tapeworms

Family Taeniidae?
Family other?
Another tapeworm group has _ intermediate hosts

Answer 11

Family Taeniidae
* Vertebrates are definitive and intermediate hosts

Family other
* Invertebrate intermediate host, vertebrate definitive host

Another tapeworm group has 2 intermediate hosts

Question 12

Family Taeniidae

segments?
larval stages?
eggs passed from the host in segments?

Answer 12

Segments square to rectangular in shape

In general, larval stages (metacestode) most
important, adults have little significance

Eggs passed from the host in segments
* Usually infection recognized from seeing segments
* Eggs seen infrequently in fecal exams
* Look the same for all family members
* Fecal flotation often negative because eggs in the segments

Question 13

How big are Cestoda eggs?

Answer 13

40micrometers

half the size of ascarid eggs

Question 14

What are the 2 common/mportant kinds of Taeniidae?

Answer 14

cysticercus

Hydatid

Question 15

Cysticercus

bladder?
production?
disease?

Answer 15

• Fluid-filled bladder
• Inverted, invaginated scolex
• 1 Cysticercus produce 1 adult tapeworm in the DH
• Infection/disease called cysticercosis

Question 16

Hydatid

bladder?
attachment?
cysts?
production?
disease?

Answer 16

• Fluid-filled bladder lines by a delicate parasitic membrane
• Heads detach from wall into cyst fluid
• Secondary cysts are formed as invaginations on the walls
• 1 hydatid produces up to thousands adult tapeworms
• Infection/disease called hydatidosis

Question 17

How do you remember Taenia Taeniaeformis

Answer 17

CATS MOUSE

• Common tapeworm of hunting cats
• Eggs shed in segments
• IH: Rodent, metacestode (Strobilocercus) in liver

Question 18

Host do you remember Taenia pisiformis

Answer 18

CANID RABBIT

• Definitive host: canids
• Egg shed in segments
• IH: Rabbits

Question 19

How do you diagnosis Taenia taeniaeformis and T. pisiformis?

Answer 19

See segments

Fecal flotation
* Quite insensitive
* Centrifugal flotation only detects 25% of the
infections (Little et al., 2015)

Question 20

Genus Echinococcus
size adults?
Metacestode stage?

Answer 20

Very small adults: 3-6 mm

Metacestode stage: Hydatid
* Undergoes asexual reproduction
* Multiple scoleces formed
* Potential for thousand of scolices to form

Question 21

Echinococcus multilocularis
location?
life cycle?

Answer 21

Northern temperate zone: northern US, Canada,
central Europe

Life cycle
* Definitive host: Fox, sometimes dog, rarely cat
* Intermediate host: Small rodents, including lagomorphs
* Humans, dogs, and pigs: aberrant or accidental IH
* Metacestode: AVEOLAR CYST (multilocular cyst)

Question 22

Echinococcus multiocularis Clinical importance?

Answer 22

*Sometimes hydatid forms in people or dogs

*Alveolar echinococcosis or alveolar hydatid
disease

*Difficult to remove surgically because grows
invasively

*New focus of infection in Ontario and Alberta

*Recently found in Virginia and Vermont

Question 23

Taenia spp. what is the definitive host?

Answer 23

Human

Question 24

Taenia saginata
size?
species?
location?

Answer 24

5-15m
human/cattle
cysticerci in bovine muscle 0.6mm

Question 25

Taenia solium
species?
location?

Answer 25

human/pig
cysticerci in pork

Question 26

Taenia solium and T. saginata clinical importance from adults?

Answer 26

• Mild abdominal discomfort
• Occur worldwide (very uncommon in the US)
• Slaughter inspection
• Cysticerci killed by cooking or periods of freezing
• Endemic cases in US rare

Question 27

Taenia solium

what happens when human ingest eggs?
human disease?
symptoms?
what continent is it prevalent?

Answer 27

• When humans ingest eggs they get cysticerci
• Causes human disease called cysticercosis or
  neurocysticercosis
• Headache, confusion, seizures
• Leading cause of adult onset epilepsy globally
• Major problem in Latin America
• Cases has occurred in the US – origin?