Tapeworms Flashcards

1
Q

Tapeworms come from which group of parasites?

A

Cestodes

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2
Q

Describe the steps in the general lifecycle of tapeworms

A
  • Adults in small intestine (they have no gut so rely on host completely)
  • Proglottids break off and eggs/proglottids shed in faeces
  • Eggs immediately infective
  • Eggs eaten by intermediate host
  • Metacestode develops in intermediate host
  • Metacestode eaten by definitive host where the adult tapeworm develops in the SI
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3
Q

Name the 4 metacestode types in the intermediate host

A
  • Cysticercus
  • Coenurus
  • Cysticercoid
  • Hydatid
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4
Q

What is a cysticercus?

A

Single evaginated protoscolex

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5
Q

What is a coenurus?

A

Complex, several protoscolices, which can all potentially develop into an adult worm

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6
Q

What is a cysticercoid?

A

Microscopic, single protoscolex, found in invertebrate intermediate host

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7
Q

What is a hydatid?

A

Highly complex, numerous protoscolices, potential for metastasis to set up another hydatid cyst

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8
Q

Name the 5 species of Taenia that dogs are the definitive host of

A
  • Taenia ovis
  • Taenia hydatigena
  • Taenia multiceps
  • Taenia pisiformis
  • Taenia serialis
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9
Q

Dogs are also the definitive host of which 3 other tapeworm spp?

A
  • Echinococcus granulosus
  • Echinococcus multilocularis
  • Dipylidium caninum
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10
Q

Cats are the definitive host of which cestode?

A

Taenia taeniformis

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11
Q

Where are adult Taenia found?

A

Small intestine

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12
Q

Describe the characteristic Taenia eggs

A

Thick embryophore, hexacanth embryo, ~40μm in diameter (these eggs are also the same as Echinococcus and can’t be differentiated)

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13
Q

Describe the morphology of Taenia

A
  • Large 30cm-5m
  • +/- armed rostellum
  • Hooks and suckers
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14
Q

How long is the PPP of Taenia?

A

4-10 weeks (spp. dependent)

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15
Q

Sheep are the intermediate host of which Taenia spp?

A

Taenia ovis
Taenia multiceps
Taenia hydatigena

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16
Q

Rabbits are the intermediate host of which Taenia spp?

A

Taenia pisiformis

Taenia serialis

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17
Q

Describe the features of a Taenia ovis infection

A
  • Cysticercus in muscles
  • ‘Sheep measles’
  • Adult tapeworm is 1.2-1.5m long
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18
Q

Describe the features of a Taenia hydatigena infection

A
  • Cysticercus in peritoneum
  • Thin necked bladder worm
  • ‘Grape’ appearance
  • Adult = 1m long
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19
Q

Describe the features of a Taenia multiceps infection

A
  • Coenurus in brain
  • Gid cyst causes neurological disease
  • Space occupying CNS lesion
  • Circling, head pressing and tilting
  • Adult = 1.2m long
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20
Q

Describe the features of a Taenia pisiformis infection

A

Cysticercus in peritoneum

Adults = 2m long

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21
Q

Describe the features of a Taenia serialis infection

A
  • Coenurus in connective and sub-cutaneous tissue

- Adult = 5m long

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22
Q

What is the intermediate host of Taenia taeniformis in cats?

A

Mouse

23
Q

Describe the features of a Taenia taeniformis infection

A
  • Cysticercus in liver
  • Adult = 60cm, bell shaped proglottids
  • PPP = 4 weeks
24
Q

How are Taenia spp diagnosed?

A
  • Rarely associated with clinical signs: anal pruritus

- Faecal sample – eggs or proglottids (10g, sampling on 3 consecutive days)

25
Q

How are Taenia spp treated and controlled?

A
  • Praziquantel treatment to remove adult tapeworm (treatment interval dictated by PPP)
  • Break the life cycle through controlling access to intermediate host/metacestode stage
26
Q

What are the two intermediate hosts of Dipylidium caninum?

A

Ctenocephalides felis - flea

Trichodectes canis - canine chewing louse

27
Q

Describe the morphology of Dipylidium caninum

A
  • 50cm long
  • Scolex: 4 unarmed suckers, protrusible rostellum bearing 4-7 rows of small hooks
  • Many segments, the gravid ones are barrel shaped (rice grains)
  • Two genital pores on each proglottid
  • Eggs packaged into capsules, each containing 10-15 eggs
28
Q

Describe the life cycle of Dipylidium caninum

A
  • Adult tapeworm in SI of cat/dog, PPP = 3-4 weeks
  • Actively motile proglottids are passed in faeces. Disintegrate and eggs released.
  • Eggs eaten by flea larvae e.g Ctenocephalides felis
  • Flea larva on floors, carpets, nooks etc
  • Oncospheres hatch and develop into cysticercoids in body cavity of adult flea
  • Infected adult flea is eaten as the dog grooms
29
Q

How is Dipylidium caninum treated?

A

Praziquantel

Flea Control!

30
Q

What spp are the definitive and intermediate hosts of Echinococcus granulosus?

A

Definitive host: dog

Intermediate hosts: sheep & cattle

31
Q

What is the definitive host of Echinococcus multilocularis?

A

Fox

32
Q

Echinococcus cause which disease type?

A

Hydatid disease

33
Q

Describe the hydatid disease of Echinococcus granulosus

A
  • Cystic/hydatid echinococcosis
  • Outer bladder wall with daughter cysts within
  • Lots of protoscolices within endogenous cysts
34
Q

Describe the hydatid disease of Echinococcus multilocularis

A
  • Alveolar echinococcosis

- Break off into smaller cysts

35
Q

Describe the morphology of adult Echinococcus

A
  • Very small – 5mm
  • Only have three proglottids + head
  • Final proglottid is largest and gravid, shed in faeces
  • Normally non-pathogenic in the dog
36
Q

Describe the morphology of Echinococcus eggs

A
  • 40 μm
  • Thick embryophore (outer wall)
  • Indistinguishable from Taenia eggs
37
Q

Describe the life cycle of Echinococcus

A
  • Metacestode with a hydatid cyst is ingested from the intermediate host
  • The protoscolices from the cyst emerge and develop into adult worms within the gut
  • They then produce all of the eggs within the final proglottid which are released into the environment where they infect the intermediate most
38
Q

What is the PPP of Echinococcus granulosus?

A

6 weeks

39
Q

What is the PPP of Echinococcus multilocularis

A

4-5 weeks

40
Q

Which Echinococcus spp is not found in the UK?

A

Echinococcus multilocularis

41
Q

Which spp are the definitive and intermediate hosts of Echinococcus multilocularis?

A

Definitive host = fox and dog

Intermediate host = small mammals/rodents

42
Q

How are Echinococcus spp diagnosed?

A
  • Rare to see clinical signs except anal pruritis

- Faecal sample – eggs or proglottids: 10g, sampling on 3 consecutive days – as egg release is slower and delayed

43
Q

How are Echinococcus spp treated and controlled?

A
  • Praziquantel treatment to remove adult tapeworm (treatment interval dictated by PPP)
  • Break the life cycle through controlling access to intermediate host/metacestode stage
  • Same as hookworms
44
Q

How do human cases of Echinococcosis (E. granulosus) occur?

A

Infection by ingesting eggs from dogs in contaminated soil, water, food

45
Q

Describe the pathogenesis of human Echinococcosis (E. granulosus)

A
  • Space occupying cyst (hydatid metacestode stage)
  • Liver, lungs, bone marrow, brain
  • Slow growing
  • Asymptomatic incubation period – several years
46
Q

What are the clinical signs of human Echinococcosis (E. granulosus)?

A
  • Clinical signs associated with location of the cyst - hepatic and pulmonary symptoms common.
  • Jaundice, cholangitis, abdominal pain
  • Pleurisy (pleural inflammation around the lungs)
  • Rupture of the cyst – fever, eosinophilia and anaphylactic reaction
47
Q

Describe the pathogenesis of human Echinococcosis (E.multilocularis)

A

Very serious pathogen in humans

  • Large, slow growing cysts - asymptomatic incubation period of 5–15 years
  • Tumour-like lesions in the liver
  • Metastasize and spread to lungs and brain
  • Invade and destroy tissues
48
Q

What are the clinical signs of human Echinococcosis (E.multilocularis)

A

Pain, Weight loss, Malaise, Liver failure

49
Q

How is human Echinococcosis diagnosed?

A
  • Ultrasonography imaging and CT/MRI scans

* Serology

50
Q

How is human cystic Echinococcosis treated?

A

Percutaneous treatment of the hydatid cysts with the PAIR (Puncture, Aspiration, Injection, Re-aspiration) technique, drug treatment, surgery

51
Q

How is human alveolar Echinococcosis treated?

A

Early diagnosis and radical (tumour-like) surgery followed by treatment with albendazole

52
Q

How is human Echinococcosis controlled?

A
  • Controlling disease in definitive and intermediate hosts
  • Improved hygiene in slaughtering animals
  • Education programmes
53
Q

What are the 3 specific PET travel scheme requirements relating to tapeworms in dogs?

A
  1. All dogs must be treated with praziquantel 1 – 5 days before ENTRY into the UK
  2. A vet must record treatment in the animal’s passport.
  3. Repeat treatment again 28 days after returning