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Parasitology > Cestodes > Flashcards

Cestodes Flashcards

1
Q

Cestodes “tapeworms”

Structure

A
  • Segmented body
  • No alimentary tract
  • hermaphroditic
  • Tegument is highly absorptive
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2
Q

Adults Cestode structure in Final Host

A

Scolex (head): Suckers, rostellum (neck), hooks (armed)- organs of attachment

Chains of segments “proglatids”. Proglatids combined are strobilia.

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3
Q

Tapeworm segements:

A

A mature segment has the reproductive organs **(mid body) **

A gravid segment contains eggs only **(tail end) **

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4
Q

Comment on a Taenia gravid segment:

A

Siegments are continually budded from the neck region. (rostellum)

Organs of sexual reproduction present in mature segment in the mid gut.

These mature segments disappear as the proglattids continue to move posteriorly until the uterus is full of eggs. It is now a **gravid segment. **

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5
Q

Taenia egg: Characteristics

A

Radially striated egg with a thick egg shell allowing resistance in the environnment.

Hexacanth (6 hooked embryo) a.k.a Oncosphere

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6
Q

Cestode life cycles:

A

Indirect

FH contains adult tapeworm (often in the SI) and passes out eggs.

IMH ingests eggs, hatch, and larval stage encysts.

FH eats the IMH containing the cyst containing head of future tapeworm

Head of future tapeworm latches on to SI and starts to bud segments.

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7
Q

Cestode larval stages in IMH

A

Metacestode or larval form

Usually in tissues (encysts)

  • cysticercus
  • coenorus
  • cysticercoid
  • hydatid
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8
Q

Family: Taeniidae

FH?

IMH?

Scolex (armed/ unarmed)?

Pathogenic?

A
  • Man, cat, dog S.I.
  • IMH: mammal- larval stages encysted.
  • Scolex: armed (except for T. saginata)
  • Adults relatively non pathogenic
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9
Q

Taenia saginata:

FH?

Armed/ Unarmed?

IMH?

Larval staged encysted in IMH?

A

FH: man

Unarmed

Cow

Cysticercus bovis: small fluid filled cyst containing a single scolex (head) therefore will give rise to one tapeworm.

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10
Q

Describe the life cycle of Taenia saginata and its PPP?

A
  1. Adults in S.I of man
  2. Pass millions of eggs per day in gravid segments (eggs are resistant, radilly striated, hexacanth 6 hooked)
  3. Eggs are ingested by susceptible bovine
  4. Oncophores release is abomasum, penetrate S.I wall
  5. Travel to skeletal muscle and encysts as Cysticercus bovis (one scolex).
  6. Takes around 12 weeks for cysts to grow and become infective.
  7. Meat is ingested by man
  8. Adults in S.I.
  9. PPP= 2-3 months
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11
Q

T. saginata Epidemiology:

A

Inadequate cooking of meat

Eggs long lived

Sanitation

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12
Q

Taenia saginata Diagnoses:

A

Meat inspection

Tend to encysts in the masster, heart, tongue, intercostal and diaphragm.

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13
Q

How can we control T. saginata?

A
  • Meat inspection
  • >25 cysts - CODEMNED
  • <25 cysts chill infected carcass at -10 C for 10 days). However if <25 cysts and dispersed all over body then condemn.
  • Cooking meat at 57 C. kills cysts
  • Restrict use of human sludge to cultivated fields or no cattle grazing for at least 2 years.
  • hygiene/ sanitation
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14
Q

Taenia solium:

FH?

IMH?

Larval encysted stage?

Lifecycle?

A

FH: man

IMH: pig or man

Cysticercus cellulosae

Lifecycle similar to T. saginata

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15
Q

Taenia solium:

Man as IMH?

A

Man can acts as IMH as well as FH.

Eggs are infective man:

  1. accidental ingestion of eggs. .
  2. Auto infection via reverse peristalisis (eggs travel back into stomach, activated, hatch, and spread around body encysting)
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16
Q

T. solium Pathology

A

Adult tapeworrm = NO PATHOLOGY

It is the encysted larvae which cause pathogenesis. Could be very serious if they encyst in the CNS or eye.

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17
Q

T. solium epidemiology

A

Close association of man and pig.

Unrestricted access of pigs to human waste.

Poor meat inspection.

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18
Q

T. solium control

A
  • Mass treatment ot kill adults worms in human (albendazole or praziquantal)
  • Mass treatment of pigs (oxfendazole)
  • Meat inspection
  • Pig corralling ( don’t allow pigs to graze on anything they want)
  • Vaccination of pigs.
  • Don’t allow pigs to graze on human sludge.
  • Try to distance areas of human and pig overlap. i.e. don’t allow pig pen close to farm house.
19
Q

Taenia multiceps:

FH?

IMH?

Larval stage encysts?

A

FH: dog

IMH: sheep

Coenorus cerebralis

Causes gid in sheep (sheep gait is altered)

20
Q

Taenia hydatigena:

FH?

IMH?

Larval encysted stage?

Where is this commonly found?

A

Dog

Sheep

Cysticercus tenuicolis

Commonly in abbatoir: persistant cause of liver condemnation.

21
Q

Taenia ovis:

FH?

IMH?

Larval encysted stage?

A

Dog

Sheep

Cysticercus ovis- causes sheep measles

First recombinant vaccine developed against helminth parasite.

22
Q
A
23
Q

Taenia Taeniaeformis:

FH?

IMH?

Larval encysted stage?

A

Cat

Mouse, rodent

Cysticercus fasciolaris

24
Q

Dipylidium caninum:

Describe the lifecycle

A
  1. Adults in S.I of dog/ cat/ man
  2. 3 weeks post infection gravid segements shed- active
  3. Gravid segments ingested by flea/ louse (lice) IMH
  4. cysticeroid in hemocoel of flea/ louse
  5. ingestion of flea/ louse by dog/ cat
  6. PPP= 3 weeks.
25
Q

Dipylidium caninum IMH:

A

Fleas- larvae not adults are the IMH because the adult mouthparts of the fleas cannot ingest eggs.

Lice: all stages

26
Q

Diagnoses of D. Caninum:

A
  1. Double genital pore. Pore on each side of the segment.
  2. Egg packets: not usually eggs in feces: membranous structure with 20+ eggs.
27
Q

Echinococcus granulosus granulosus

FH?

Site?

IMH?

Zoonosis?

Echinococcus granulosus equinus

FH?

Site?

IMH?

Zoonosis?

A

E.g.g:

dog, wild canid

SI

ruminants, pig, man

Zoonotic

E.g.e:

dog, red fox

SI

horse, donkey

Not Zoonotic.

28
Q

Echinococcus adult/ egg characteristics:

A

Adult: scolex plus 3-4 segments. Very big gravid segment

Egg: Similar to Taenia (radially striated) 6 hook hexacanth

29
Q

Describe the lifecycle of E.g. granulosus and its PPP?

A
  1. Adults in S.I dog
  2. Gravid segments **shed 1 per week **
  3. Egg is very resistant.
  4. Ingested by IMH (pig, man, ruminant)
  5. Onchosphere released and penetrates the S.I wall of IMH
  6. Hydatid cysts in IMH liver/ lungs approx 6+ months post infection
  7. Cysts are ingested by host
  8. Heads (scolex) erupt from cyst and attach to FH S.I.
  9. **PPP= 40-50 days. **
30
Q

Pathology of E.g.g associated with?

A

Associated with cysts not adult worms.

31
Q

Comment on hydatid cysts in IMH.

A

Hydatid cysts can contain thousands of heads “ hydatid sand”

32
Q

How can we diagnose E. granulosus?

A

IMH- abbatoir

FH: FEC, Copro-Ag test, Copro-PCR

33
Q

E. g. granulosus pathogensis:

A

Mostly well tolerated in the IMH unless cysts in usual site.

Most cases are detected in abbatoir.

Not pathogenic in dog final host.

Always of signifcance in humans.

34
Q

E. g. granulosis Epidemiology

Domestic?

Sylvatic?

A

Domestic:

FH: Dog

IMH: Sheep

Dog can infect man

Sylvatic:

FH: wild canid

IMH: ruminant

maintained by predation/ carrion feeding.

35
Q

E. g. equinus epidemiology

A

FH: dog/ red fox

IMH: horse/ donkey

Transmitted via equine abbatoirs/ hunting kennels. Maintained by feeding hunting dogs equine viscera.

36
Q

E. g. granulosis is zoonotic.

Man as IMH?

A

Man is accidental IMH. Most likely infected by close quarters with infected dog via oncospheres in water, hair, or foodstuffs.

37
Q

How can we control hydatid disease?

A

Regular deworming of dogs with praziquantal

Proper disposal of infected carcasses

Deny access of dogs to abbatoirs.

38
Q

Echinococcus multiocularis:

FH?

IMH?

LIfecycle?

Zoonotic?

A

FH: dog, cat, wild canid

IMH: rodent, man

Life cycle similar to E. g. g

Zoonotic

39
Q

Describe the events in E. multiocularis life cycle and its PPP?

A
  1. Adults in S.I fox
  2. Gravid segments shed in feces
  3. Eggs resistant up to -50 C.
  4. Ingested by rodent IMH
  5. Hexacanth released penetrates S.I. Wall
  6. Travles to liver via Hepatic portal vein. Rapidly vesiculates in the liver.
  7. Cyst ingested by fox from predation on rodent.
  8. Scolex erupts from cyst and attaches to fox S.I.
  9. **PPP= 28-35 days (4-5 weeks) **
40
Q

Pet passport and Echinococcus multiocularis:

A

Cat and dogs must be treated for E. multiocularis by dosing with praziquantal 24-48 hours prior to travel in the UK.

41
Q

Cestodes of the Horse:

Anopolocephala perfoliata

What climates do they prefer?

What pathology do they cause?

Whats a concern/ risk factor in horses due to them?

Characteristics of adults?

A

high prevalance in temperate climates.

Ulcerations at site of attachements

Risk factor for ileo-cecal colic (ulceration at that junction)

Flat, short segemented.

42
Q

Describe the events in the lifecyle of Anoplocephala perforliata and its PPP?

A
  1. Adults at ileo-cecal junction.
  2. egg passed in feces
  3. Ingested by forage mite IMH
  4. Forms cysticercoid cyst in mite.
  5. Infected mite ingested by horse when grazing.
  6. Head emerges from cyst and attaches to gut wall at ileo-cecal junction forming ulceration.
  7. **PPP= 6-10 weeks. **
43
Q

A. perfoliata and Colic.

A

Horses with tapeworms are more likely to suffer colic.

44
Q

How can we diagnose A. perfoliata in horses?

A
  1. FEC: Low sensitivity, high specificity (if test positive then proceed to ELISA.
  2. ELISA
  3. Copro- Ag PCR

Egg contains a pyriform apparatus that it sits on. Egg is also mishapen.

Parasitology (10 decks)

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