Taeniids Flashcards
Who is in the family Taeniidae & who are their hosts?
- Taenia spp. - Ca & Fe
- Echinococcus spp - Ca (Fe)
What features do Taeniid type eggs have?
- thick radially striated shell
- hooks on hexacanth larva
What is a diagnostic feature of Taeniids?
single genital pore
Body layout of an adult Taenid?
scolex -> immature segments -> mature segments -> gravid segments
Adult tapeworms can be ID’d based on?
hook morphology
Important features on the scolex (head) of Taeniids are?
rostellum w/ hooks, suckers
Describe the mature segments of Taenia:
- one set of genitalia per segment (ovary, testes, uterus, lateral genital pore, ootype, & vitelline gland)
- they are hermaphrodites
Describe the gravid segments of Taenia:
- released in host feces
- branched uterus (like a tree)
- single lateral genital pore
Life cycle of Taenia spp?
- 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
What are the most common tapeworms in pets in Canada?
T. pisiformis & T. taeniaeformis
What is the definitive host of Taenia hydatigena?
canids
What is the metacestode of Taenia hydatigena?
cysticercus
What is the intermediate host of Taenia hydatigena?
domestic & wild Ru
What is the location of the larvae in the intermediate host of Taenia hydatigena?
liver, peritoneum
What is the definitive host of T. pisiformis?
canids
What is the metacestode of T. pisiformis?
cysticercus
What is the intermediate host of T. pisiformis?
rodents & rabbits
What is the location of the larvae in the intermediate host of T. pisiformis?
liver, peritoneum
What is the definitive host of T. ovis?
canids
What is the metacestode of T. ovis?
cysticercus
What is the intermediate host of T. ovis?
sheep, goat
What is the location of the larvae in the intermediate host of T. ovis?
muscle
What is the definitive host of T. krabbei?
canids
What is the metacestode of T. krabbei?
cysticercus
What is the intermediate host of T. krabbei?
cervids
What is the location of the larvae in the intermediate host of T. krabbei?
muscle
What is the definitive host of T. serialis?
canids
What is the metacestode of T. serialis?
coenurus
What is the intermediate host of T. serialis?
rabbits
What is the location of the larvae in the intermediate host of T. serialis?
CT
What is the definitive host of T. taeniaeformis?
felids
What is the metacestode of T. taeniaeformis?
strobilocercus
What is the intermediate host of T. taeniaeformis?
rodents
What is the location of the larvae in the intermediate host of T. taeniaeformis?
liver
What is a cyclophyllid metacestode?
the type of larvae in the intermediate host
what are the different types of cyclophyllid metacestodes?
- cysticercoid (single protoscolex, no cyst)
- cysticercus (single protoscolex, fluid-filled cyst)
- coenurus (many protoscolices attached to the wall of at fluid-filled cyst)
- strobilocercus (miniature adult, no cyst)
- cystic hydatid (many protoscolices free in fluid filled cyst)
- alveolar hydatid (many protoscolices free in multichambered fluid-filled cysts)
How do you diagnose & what are the clinical signs of Taenia spp in the definitive host (Ca or Fe)?
- 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
What is the control & treatment of Taenia in definitive hosts?
- 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
What is the control & treatment of Taenia in intermediate hosts?
- 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
What is the epidemiology/ecology of Taeniidae?
- 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
What are the Echinococcus spp?
- Echinococcus granulosus/ E. canadensis (other important spp/ strains circulate in livestock & Ca elsewhere in the world)
- Echinococcus multilocularis
What are the definitive & intermediate hosts of Echinococcus granulosus/ E. canadensis?
- definitive hosts: wolves, coyotes, Ca
- IH: moose, elk, caribou, deer, (people)
What are the definitive & intermediate hosts of Echinococcus multilocularis?
- DH: fox, coyotes, wolves, Ca, (Fe)
- IH: rodents, (Ca, people)
Can the eggs of Taenia spp and Echinococcus spp (zoonotic) be distinguished?
NO!
How do you determine btwn E. granulosus & E. multilocularis body segments?
- 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
What is the life cycle of Echinococcus canadensis?
- 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)
What type of metacestodes can Taenia spp have?
- Cysticercus, coenurus, strobilocercus
What type of metacestodes can Echinococcus spp have?
Cystic hydatid
How do you diagnose & what are the clinical signs of Echinococcus spp in the definitive host (Ca)?
- 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?
What should you do before handling the intestines of feces of wild canids & why?
- pretreat @ -80 C for 5 days because of Echinococcus
What is the epidemiology/ecology of E. canadensis?
- 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
What is the distribution of Echinococcus multilocularis in Canada?
- all of western Canada is now considered endemic (maybe not Vancouver Island)
- also in southern Ontario
What is the life cycle of Echinococcus multilocularis?
- 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)
what kind of metacestode does Echinococcus multilocularis develop into?
alveolar hydatid
What is unique about Echinococcus multilocularis in Ca?
Ca can be either the definitive host OR the intermediate host & develop alveolar echinococcosis after ingesting infective eggs
How common is Ca alveolar echinococcosis in Canada & how is it detected?
- cases are becoming increasingly common in AB, SK, ON, BC, & MB
- initially detected on medical imaging
- sometimes detected on laparotomy
- sometimes detected on necropsy
how is Ca alveolar echinococcosis diagnosed?
- 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)
What is your suspicion with this ultrasound?
Alveolar echinococcosis
How do you detect alveolar echinococcosis on histo?
- if protoscolices are detected, probably diagnosis of Alveolar echinococcosis
- but many Alveolar echinococcosis dogs lack protoscolices
How do you get a definitive diagnosis of Echinococcus with PCR?
- 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
How do you manage Ca Alveolar echinococcosis?
- 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
How do we control for Echinococcus in the definitive host (Ca)?
- 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)
What is a high risk dog for Echinococcus?
- 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)
