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Parasitology > Taeniids > Flashcards

Taeniids Flashcards

1
Q

Who is in the family Taeniidae & who are their hosts?

A
  • Taenia spp. - Ca & Fe
  • Echinococcus spp - Ca (Fe)
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2
Q

What features do Taeniid type eggs have?

A
  • thick radially striated shell
  • hooks on hexacanth larva
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3
Q

What is a diagnostic feature of Taeniids?

A

single genital pore

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4
Q

Body layout of an adult Taenid?

A

scolex -> immature segments -> mature segments -> gravid segments

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5
Q

Adult tapeworms can be ID’d based on?

A

hook morphology

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6
Q

Important features on the scolex (head) of Taeniids are?

A

rostellum w/ hooks, suckers

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7
Q

Describe the mature segments of Taenia:

A
  • one set of genitalia per segment (ovary, testes, uterus, lateral genital pore, ootype, & vitelline gland)
  • they are hermaphrodites
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8
Q

Describe the gravid segments of Taenia:

A
  • released in host feces
  • branched uterus (like a tree)
  • single lateral genital pore
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9
Q

Life cycle of Taenia spp?

A
  • PPP = 6-9 wks
  • Gravid segments & eggs are passed in the feces (eggs contain a single hexacanth larvae) -> ingested by intermediate host (develops into some sort of metacestode larvae w/ protoscolex/(ices)) -> develops in intermediate host for 2-3 months -> intermediate host is ingested by definitive host (ex: Ca) -> adults develop in definitive host
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10
Q

What are the most common tapeworms in pets in Canada?

A

T. pisiformis & T. taeniaeformis

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11
Q

What is the definitive host of Taenia hydatigena?

A

canids

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12
Q

What is the metacestode of Taenia hydatigena?

A

cysticercus

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13
Q

What is the intermediate host of Taenia hydatigena?

A

domestic & wild Ru

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14
Q

What is the location of the larvae in the intermediate host of Taenia hydatigena?

A

liver, peritoneum

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15
Q

What is the definitive host of T. pisiformis?

A

canids

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16
Q

What is the metacestode of T. pisiformis?

A

cysticercus

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17
Q

What is the intermediate host of T. pisiformis?

A

rodents & rabbits

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18
Q

What is the location of the larvae in the intermediate host of T. pisiformis?

A

liver, peritoneum

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19
Q

What is the definitive host of T. ovis?

A

canids

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20
Q

What is the metacestode of T. ovis?

A

cysticercus

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21
Q

What is the intermediate host of T. ovis?

A

sheep, goat

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22
Q

What is the location of the larvae in the intermediate host of T. ovis?

A

muscle

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23
Q

What is the definitive host of T. krabbei?

A

canids

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24
Q

What is the metacestode of T. krabbei?

A

cysticercus

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25
Q

What is the intermediate host of T. krabbei?

A

cervids

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26
Q

What is the location of the larvae in the intermediate host of T. krabbei?

A

muscle

27
Q

What is the definitive host of T. serialis?

A

canids

28
Q

What is the metacestode of T. serialis?

A

coenurus

29
Q

What is the intermediate host of T. serialis?

A

rabbits

30
Q

What is the location of the larvae in the intermediate host of T. serialis?

A

CT

31
Q

What is the definitive host of T. taeniaeformis?

A

felids

32
Q

What is the metacestode of T. taeniaeformis?

A

strobilocercus

33
Q

What is the intermediate host of T. taeniaeformis?

A

rodents

34
Q

What is the location of the larvae in the intermediate host of T. taeniaeformis?

A

liver

35
Q

What is a cyclophyllid metacestode?

A

the type of larvae in the intermediate host

36
Q

what are the different types of cyclophyllid metacestodes?

A
  1. cysticercoid (single protoscolex, no cyst)
  2. cysticercus (single protoscolex, fluid-filled cyst)
  3. coenurus (many protoscolices attached to the wall of at fluid-filled cyst)
  4. strobilocercus (miniature adult, no cyst)
  5. cystic hydatid (many protoscolices free in fluid filled cyst)
  6. alveolar hydatid (many protoscolices free in multichambered fluid-filled cysts)
37
Q

How do you diagnose & what are the clinical signs of Taenia spp in the definitive host (Ca or Fe)?

A
  • almost invariable subclinical
  • fecal floatation for eggs (not sensitive (20-30%; use high specific gravity solution >1.3 or sedimentation); not specific - morphologically identical to Echinococcus (which is potentially zoonotic))
  • dont do perianal tape mount (may accidentally ingest egg)
  • coproAg or coproPCR
  • segments or adult cestodes in feces or on necropsy
38
Q

What is the control & treatment of Taenia in definitive hosts?

A
  • any free-roaming pet w/ access to intermediate hosts or raw meat is at risk
  • several cestocides are labeled for Ca & Fe (espirantel, fenbendazole, praziquantel)
  • goal: halt environmental contamination w/ immediately infective, resistant eggs
  • control: prevent access to intermediate hosts, cook or freeze offal & meat before feeding to Ca
39
Q

What is the control & treatment of Taenia in intermediate hosts?

A
  • generally found on meat inspection of intermediate hosts
  • control: no treatment available for intermediate hosts; prevent access to food & water contaminated w/ feces of the definitive host
40
Q

What is the epidemiology/ecology of Taeniidae?

A
  • prevalence is less affected by the age of the host
  • global distribution
  • sp-specific host assemblages
  • predator-prey INDIRECT life cycles: carnivore definitive hosts & herbivore intermediate hosts
  • eggs are immediately infective & very resistant
41
Q

What are the Echinococcus spp?

A
  • Echinococcus granulosus/ E. canadensis (other important spp/ strains circulate in livestock & Ca elsewhere in the world)
  • Echinococcus multilocularis
42
Q

What are the definitive & intermediate hosts of Echinococcus granulosus/ E. canadensis?

A
  • definitive hosts: wolves, coyotes, Ca
  • IH: moose, elk, caribou, deer, (people)
43
Q

What are the definitive & intermediate hosts of Echinococcus multilocularis?

A
  • DH: fox, coyotes, wolves, Ca, (Fe)
  • IH: rodents, (Ca, people)
44
Q

Can the eggs of Taenia spp and Echinococcus spp (zoonotic) be distinguished?

A

NO!

45
Q

How do you determine btwn E. granulosus & E. multilocularis body segments?

A
  • Granulosus has lateral genital pore in the caudal half of its mature segments
  • Multilocularis has lateral genital pore in the cranial half of its mature segments
46
Q

What is the life cycle of Echinococcus canadensis?

A
  • PPP ~6 wks in DH
  • DH (wolf, coyote, or Ca) passes infective eggs in feces -> ingested by IH (develops into cystic echinococcus -> develops for 6-12 m in IH (moose > caribou > elk > deer)) OR ingested by human (becomes cystic echinococcus (CE) in lungs, liver, or other)
47
Q

What type of metacestodes can Taenia spp have?

A
  • Cysticercus, coenurus, strobilocercus
48
Q

What type of metacestodes can Echinococcus spp have?

A

Cystic hydatid

49
Q

How do you diagnose & what are the clinical signs of Echinococcus spp in the definitive host (Ca)?

A
  • almost invariably subclinical
  • fecal floatation for eggs (low sensitivity, 17-27%; eggs are morphologically identical to Taenia spp.)
  • CoproPCR (higher sensitivity, > 80%) & can distinguish between Taenia & 2 Echinococcus spp (suggested method)
  • adult cestodes in feces or on necropsy?
50
Q

What should you do before handling the intestines of feces of wild canids & why?

A
  • pretreat @ -80 C for 5 days because of Echinococcus
51
Q

What is the epidemiology/ecology of E. canadensis?

A
  • all across Canada
  • only sp present in Canada
  • prevalence tends to increase w/ age
  • predator-prey indirect life cycle (Carnivore DH & herbivore IH)
  • eggs are immediately infective & very resistant
52
Q

What is the distribution of Echinococcus multilocularis in Canada?

A
  • all of western Canada is now considered endemic (maybe not Vancouver Island)
  • also in southern Ontario
53
Q

What is the life cycle of Echinococcus multilocularis?

A
  • PPP = 35 days
  • infective eggs are passed in the feces of DH (Fox, coyote, wolf, Ca, (Fe)) -> ingested by IH (develops over 2-4 m into alveolar echinococcosis (in lemmings, voles, deer mice, & others)) OR ingested by people (develops into alveolar echinococcosis in Liver, or other)
54
Q

what kind of metacestode does Echinococcus multilocularis develop into?

A

alveolar hydatid

55
Q

What is unique about Echinococcus multilocularis in Ca?

A

Ca can be either the definitive host OR the intermediate host & develop alveolar echinococcosis after ingesting infective eggs

56
Q

How common is Ca alveolar echinococcosis in Canada & how is it detected?

A
  • cases are becoming increasingly common in AB, SK, ON, BC, & MB
  • initially detected on medical imaging
  • sometimes detected on laparotomy
  • sometimes detected on necropsy
57
Q

how is Ca alveolar echinococcosis diagnosed?

A
  • suspicion: medical imaging, liver mass in young Ca (ddx: neoplasia, granuloma, other causes of cysts)
  • suggestive: serology (not routinely available in NA), histopathology (protoscolices are only present in ~ 1/3rd of Ca; periodic acid-Schiff (PAS) stain can be used to detect membrane; calcareous corpuscles; potential for misdiagnosis w/ other larval cestodes)
  • definitive: immunohistochemistry (not routinely available in NA), PCR (abdominocentesis fluid; aspirated cyst contents; biopsy, surgical resection)
58
Q

What is your suspicion with this ultrasound?

A

Alveolar echinococcosis

59
Q

How do you detect alveolar echinococcosis on histo?

A
  • if protoscolices are detected, probably diagnosis of Alveolar echinococcosis
  • but many Alveolar echinococcosis dogs lack protoscolices
60
Q

How do you get a definitive diagnosis of Echinococcus with PCR?

A
  • on tissue or fluid from Alveolar echinococcosis (in Ca acting as the intermediate host)
  • on feces from Ca acting as DH (E. multilocularis vs E. granulosus vs Taenia spp.)
  • screening multiplex PCR is offered @ WCVM, Calgary, Guelph, Idexx, & Antech
61
Q

How do you manage Ca Alveolar echinococcosis?

A
  • collect fecal sample for floatation & COPROPCR
  • treat w/ adult cestocide (initially; ex: praziquantel @ 5 mg/kg SID for 2 days) - when you find AE also suspect adults
  • treat w/ larval cestocide (long-term/life-long; ex: albendazole @ 10 mg/kg SID)
  • surgical debulking / resection if clinically indicated
  • advise O to consult health care provider
  • poor prognostic indicators: late detection, significant abdominal effusion, metastases
62
Q

How do we control for Echinococcus in the definitive host (Ca)?

A
  • goal: halt environmental contamination w/ immediately infective, highly resistant eggs (resistant to most chemicals (try strong bleach?); killed by heat, drying, & freezing below -80 C)
  • control: prevent access to IH (freeze or cook offal)
  • why treat? primarily due to public health concerns
  • w/ what? praziquantel - high efficacy against adults
  • who & where? high risk dogs in endemic areas (free-roaming, hunting, scavenging, raw meat)
  • when? high risk: prophylactically, year round, every 4-6 wks (known positive: eggs may shed for 3 days post treatment; advise O to consult health care provider)
63
Q

What is a high risk dog for Echinococcus?

A
  • Does the Ca live in or travel to an endemic region? (all of western canada)
  • Does the Ca eat cervid carcasses? (if YES, rx praziquantel w/in 4-6 wks of exposure; AT RISK FOR E. canadensis)
  • Does the Ca eat wild rodents? (if YES, rx praziquantel monthly, year round; AT RISK FOR E. multilocularis)
  • Does the dog have contact w/ coyote/fox/wolf/dog feces? (If YES, HIGH RISK OF Alveolar echinococcosis; NO PHARMACEUTICAL PREVENTION POSSIBLE)

Parasitology (13 decks)

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