Veterinary Parasitology - Cestodes

Front 1

Describe the morphological characteristics of cestodes.

Back 1

Adults in the SI, ILC generally (only 2 exceptions). Don't have a body cavity, organs supported by a cellular parenchyma. Surface of the cestode covered by tegument, which allows nutrient absorption and waste excretion. Also have a flame cell system. Have a scolex, neck and strobila. Each segment is hermaphrodite.

Front 2

What is protandry?

Back 2

Male organs develop first in the cestode segments.

Front 3

Describe the eggs of the Cyclophyllidea.

Back 3

Eggs aren't released until the uterus is full, it then breaks off and passes out. Cyclophyllidean eggs have a thin outer membrane, the next layer is a thick embryophore enclosing the hexacanth embryo

Front 4

Describe the eggs of the Pseudophyllidea.

Back 4

Gravid segments remain attached, so eggs pass out through the uterine pore of the segment and are passed. Eggs have a shell with a single operculum. A period of development outside the host is necessary before the embryo (known as a coracidium) is developed.

Front 5

Describe the scolex of Cyclophyllidea.

Back 5

4 suckers present, sometimes armed with hooks. Most spp have a rostellum armed with one or more rows of hooks.

Front 6

Describe the reproductive organs of Cyclophyllidea.

Back 6

One or two sets of male and female organs may be present. Males have a protusable cirrus which protudes through the genital pore (on the lateral side). Gravid proglottids are dropped off

Front 7

Describe the scolex of Pseudophyllidea.

Back 7

Has two longitudinal sucker grooves (bothria). NO HOOKS AND NO ROSTELLUM.

Front 8

Describe the reproductive organs of Pseudophyllidea.

Back 8

Only one set per segment. Similar to Cyclophyllidea, but the uterus opens at the uterine pore which is located in the midline of the segment. Eggs once fertilized don't accumulate but are discharged.

Front 9

What is the receptaculum seminis?

Back 9

Holding facility for sperm.

Front 10

What are the vitellaria and Mehlis' glands?

Back 10

They add the yolk and shell material to the eggs.

Front 11

Cysticercus

Back 11

Fluid-filled bladder-like cyst into which one protoscolex is invaginated. Occurs in VERTEBRATE IH only

Front 12

Cysticercoid

Back 12

Similar to cysticercus, but the cyst doesn't contain fluid and closely enfolds one protoscolex. Occurs in INVERTEBRATE IH only.

Front 13

Coenurus

Back 13

A fluid-filled cyst lined by a germinal membrane from which are budded many protoscolices. These remain attached to the germinal layer and are not grouped in capsules. Occurs in VERTEBRATE IH only.

Front 14

Hydatid cyst

Back 14

A fluid-filled cyst lined by germinal membrane, and has a thick outer layer. The germinal membarne produces may protoscolices which bud off and contain a germinacl membrane of their own (brood capsules). Often contain hydatid sand in the bottom. Occurs in VERTEBRATE IH only.

Front 15

What is hydatid sand?

Back 15

Single solices, brood capsules and daughter cysts

Front 16

What is special about the cyst formed in Echinococcus multilocularis

Back 16

Similar to a hydatid cyst, but the thick outer layer is absent. The cyst wall proliferates new cysts outside as well as protoscolices inside. Metastasizes very easily.

Front 17

What gut factor causes evagination of the protoscolices?

Back 17

Bile salts

Front 18

What stage of a cestode is passed in the faeces of the DH?

Back 18

Gravid segment containing infective eggs.

Front 19

What stage is infective for the IH?

Back 19

Egg containing a hexacanth embryo.

Front 20

What stage is infective for the DH?

Back 20

Protoscolex contained in a cyst of some type.

Front 21

Describe the morphology of the family Taeniidae.
Hint: its a Cyclophyllidae

Back 21

Scolex has 4 suckers not armed by hooks and a fixed rostellum with two rows of hooks. One set of genitalia per segment, genital pores alternate down each side, the gravid segments are longer than wide and the eggs persist in the uterus. Larvae are everything BUT A CYSTICERCOID.

Front 22

Taenia hydatigena

Back 22

Usually less than a metre long. DH are dogs, IH are sheep, cattle, pigs, deer. Cysticercus tenuicollis larva. Cysts found in the abdominal cavity of the IH. Egg hatches in the SI of the IH, migrates in the portal blood to the liver, migrates around in the liver, breaks through and falls into the abdominal cavity.

Front 23

Taenia ovis

Back 23

Usually less than a metre long. DH are dogs, IH are sheep/goats. Cysticercus ovis larva. Cysts found in the IM connective tissue of the IH. Often in the heart and diaphragm. No involvment of the liver.

Front 24

Taenia taeniaeformis

Back 24

About 60cm long. DH are cats, IH are mice and rats. Cysicercus fasiolaris larvae - modified cysticercus. Cysts are found in the liver of the IH.

Front 25

Taenia saginata

Back 25

About 25cm long. DH are humans, IH are oxen. Cysticercus bovis larvae. Cysts are found in the IM connective tissue, often in the tongue, heart and masseter muscles.

NB very distinctive in that the scolex and larval protoscolexhave no rostellum and no hooks.

Front 26

Taenia solium

Back 26

Up to 7 metres long. DH are humans, IH are pigs. Cysticercus cellulosae larvae. Cysts are found in the IM connective tissue.

Front 27

What is unique about Echinococcus granulosus - the hydatid tapeworm - compared to other members of Taeniidae?

Back 27

Echinococcus is very small, only 4-6mm, others are well over a couple of metres.

Front 28

Echinococcus granulous

Back 28

DH are dogs and its close relatives, IH are normally ungulates. Cyts usually form in the liver and lungs. Distinguished from other cestode cysts by having a thick laminated layer. Layers in the cyst are germina, laminated and adventitious layer. Human infection occurs from the ingestion of faeces from infected dogs, the cyts in animals aren't dangerous.

Front 29

What are the morphological characteristics of Dilepididae?

Back 29

About 20cm long. DH are cats and dogs, IH are larvae of fleas or lice. Scolex has a retractable rostellum armed with 4-6 rows of thorn shaped hooks. Segments have duplicate sets of genitalia with a genital pore both sides on each segment. Gravid segments contain eggs in capsules.

Front 30

How would you differentiate Dipylidium caninum from Taeniidae?

Back 30

The rows of hooks on Dipylidium.

Front 31

What larvae does D. caninum produce?

Back 31

Cysticercoid, which persisit in the flea or louse as it moults to the adult. DH becomes infected by ingesting the IH.

Front 32

What are the morphological characteristics of Anoplocephalidae

Back 32

DH are ruminants and horses, IH are free-living pasture mites.

Front 33

Anophocephala perfoliata

Back 33

Adults found in the ileocaecal junction of horses. About 8-10 cm. Looks rather like short pieces of fettucini. Doesn't have a rostellum, and doesn't have hooks.

Front 34

Monezia

Back 34

Adults found in the SI of ruminants. Scolex has no rostellum and no hooks. Larvae are cysticercoid.

M. expansa and M. benedeni infect sheep, goats and cattle.

Front 35

Davainea proglottina

Back 35

The most pathogenic cestode of poultry. Only 4mm or so, IH are slugs/snails.

Front 36

Raillietina spp

Back 36

Not as pathogenic as Davainea. IH are beetles, ants, cockroaches and flies.

Front 37

Describe the differences between Pseudophyllidea and Cyclophyllidea.

Back 37

The scolex has two longitudinal sucking grooves (bothria) instead of 4 suckers. There are no hooks. The genital pore is centrally placed in each segment, and the eggs are shed while the segments are still attached. Eggs are operculate and resemble trematode eggs, but contain a coracidium with 6 hooks. Their life cycle involves 3 larval stages (coracidium, procercoid, plerocercoid) and 2 intermediate hosts (the first is an invertebrate, the second a vertebrate)

Front 38

What does develops inside a pseudophyllidea egg if it reaches water?

Back 38

A coracidium (a round ciliated thing). Hatches in water in response to light. Swims around looking for an aquatic crustacean.

Front 39

What is the stage that develops in the crustacean?

Back 39

Procercoid, which is a solid bodied larvae with 6 hooks.

Front 40

What is needed for the procercoid to develop further?

Back 40

The crustacean must be eaten by a second IH (fish, amphibian or reptile) and then the procercoid will develop into a plerocercoid usually in the hosts muscles.

Front 41

Describe the pleurocercoid.

Back 41

Elongated with a scolex invaginated at one end.

Front 42

Diphyllobothrium latum

Back 42

First IH is a freshwater crustacean, second is a freshwater fish. DH are humans, dogs and cats. Occurs commonly in countries which eat raw, dried or smoked fish. NOT IN NZ.

Way to remember, latum is a brand of pickled herring.

Front 43

Spirometra erinacei

Back 43

First IH is a FW crustacean, second IH are a number of vertebrates inc. frogs, lizards, snakes, rodents, marsupials, pigs etc. DH are dogs and cats (and other canid relatives). Humans can become infected (known as sparganosis by eating undercooked pork.

Front 44

Describe the morphology of the phylum Acanthocephala.

Back 44

Commonly known as thorny headed worms. Adults are in the small intestine. They look like a nematode, but have a thick tegument and no alimentary tract. Anterior end has a hooked proboscis. SEXES ARE SEPARATE. Fertilised eggs are discharged containing a thick shell.

Front 45

Describe the LC of Acanthocephala.

Back 45

LC involves crustaceans as IH for aquatic life or seabirds. IH are cockroaches and such for terrestrial DHs.

Front 46

Macracanthorhynchus hirudinaceus.

Back 46

IH are dung beetles, cockroaches etc. DH are pigs. Adults in the SI. Females are very large

Front 47

Describe the general morphology of digean termatodes.

Back 47

Unsegmented, most are flattened dorso-ventrally, some are fleshy. Body is covered by a complex tegument containing spines. No body cavity, all organs are supported by a cellular parenchyma. Oral sucker for feeding, ventral sucker for attachment. Alimentary system, containing two blind-ending caeca. NO ANUS. Regurgitation of waste, osmoregulation by flame cells.

Front 48

Describe the reproductive systems of digean trematodes.

Back 48

All (except Schisotosomatidae) are hermaphrodites. Males have 2 testes, females have 1 ovary. All trematode (except Schistostomadtidae) have an operculum at one end.

Front 49

Describe the digean LC.

Back 49

ALWAYS INDIRECT, with a snail (often aquatic) as the first IH. Some spp have have second and third IHs.

Front 50

What are the stages in the digean trematode LC.

Back 50

Egg, miracidium, sporocyst, redia, cercaria, metacercaria.

Front 51

What do digean trematode eggs contain when laid?

Back 51

Morula.

Front 52

Describe the sporocyst.

Back 52

Sac-like structure lined by germinal cells which produce redia, which burst through the sporocyst wall.

Front 53

Describe the redia.

Back 53

Elongated, has a mouth and simple gut. Motile and migrates to the hepato-pancreas of the IH. Cercaria produced leave via a birth pore.

Front 54

Describe the cercaria.

Back 54

Have a body and tail, look somewhat like sperm. The body has suckers, a gut and flame cells. The cercaria leave the snail and infect the DH once they are metacercaria.

Front 55

Describe the three situations where encystment occurs.

Back 55

On vegetation, on or in the first IH, on or in the second IH.

Front 56

How does Schisotsomatidae infect its DH?

Back 56

Cercaria penetrate the skin.

Front 57

What are almost all digean LCs dependent on?

Back 57

Water.

Front 58

Which trematode makes ants go all crazy?

Back 58

Dicrocoelium dendriticum (not in NZ).

Front 59

Trematodes are hightly IH host specific. True or False?

Back 59

True.

Front 60

Describe the general morphology of the family fasciolidae.

Back 60

Quite large, flat, leaf-like flukes often with an anterior conical projection. Caecae and gonads are much branched. Adults inhabit the bile duct or intestine.

Front 61

Fascioloides magna

Back 61

Bile ducts of ruminants and horses in the USA/Europe.

Front 62

Fasciolopsis buski

Back 62

SI of man in S.E. Asia.