8. D/C - Taeniid Cestodes

Question 1

What is the epidemiology and ecology of taeniids?

Answer 1

Adults found in both canids and felids. larval stages found in a variety of hosts
Global distribution
predator-prey based indirect life cycles: carnivore as DH and herbivore as IH
eggs immediately infective and resistant in enviro for months

Question 2

Do taenia species require asexual or sexual reproduction

Answer 2

they are hermaphrodites and each mature segment has one set of genitalia

Question 3

What is the life cycle of taenia spp?

Answer 3

PPP 6-9wks
2-3mo develop in IH
Adults shed gravid segments and eggs in their feces. Eggs contain a single hexacanth larvae, which is ingested by the IH (with metacestode with protoscolex) and are then ingested by the DH

Question 4

How do we diagnose animals with taenia spp? What about clinical signs?

Answer 4

Almost always subclinical
fecal float for eggs - not sensitive (20-30%) (use high specific gravity solution >1.3, or sedimentation), not specific - morphologically identical to echinococcus
Coproantigen or coproPCR
segments or adult cestodes in feces or on necropsy (fairly easy to determine genus - usually set to lab to determine species)

Question 5

What does a taeniid egg look like?

Answer 5

Relatively round to slightly oval.
Has a thick radially striated shell and inside, there are hooks on the hexacanth larva
about 20 micrometers big

Question 6

How can we control and treat taenia?

Answer 6

DH - animals @ risk are any free-roaming pet w/ access to IH, potentially raw meat diets
GOAL: halt enviro contam w/ immediately infective, resistant eggs
Several cestocides labels for dogs and cats will kill adult tapeworms
CONTROL: prevent access to IH, cook/freeze offal and meat before feeding to dogs
No pharmaceutical measures for IH host
Remember, this cycles wherever wild hosts are present. spp is not zoonotic

Question 7

What are the DH and IH of echinococcus granulosus/E. canadensis?

Answer 7

DH: wolves, coyotes, dogs
IH: Sheep, moose, elk, caribou, deer, (people)

Question 8

What are the IH and DH for echinococcus multilocularis?

Answer 8

DH: fox, coyotes, wolves, dogs, (Cats)
IH: rodents (dogs, people)

Question 9

What is the epidemiology and ecology of E. canadensis

Answer 9

All across canada except NL (so far)
E. canadensis is only species present in Canada (11% of dogs in eastern SK reserve community, 70% of wolves to 30% of coyotes)
prevalence tends to inc w/ age
predator-prey indirect life cycles, eggs immediately infective and very resistant

Question 10

Describe the life cycle of echinococcus canadensis?

Answer 10

PPP ~6wks
Canid DH -> feces w/ infective eggs> Infective host & develops for 6-12 mo > cystic hydatid > ingested by DH

Question 11

What is a cystic hydatid?

Answer 11

many protoscolices free in a fluid-filled cyst

Question 12

What must we do of wild canids before we can open the intestines or handle feces?

Answer 12

Pretreat at -80C for 5 days

Question 13

What are the diagnosis and clinical signs of echinococcus spp in DH (Dog_

Answer 13

almost invariably subclinical
Fecal float for eggs (low sensitivity, 17-27%), eggs similar to taenia spp
CoproPCR (higher sensitivity, >80%) and can distinguish among taenia and 2 echinococcus spp

Question 14

Where does a hydatid cyst live in a human?

Answer 14

lungs, liver, other places

Question 15

What is the distribution of echinococcus multilocularis and its prevalence?

Answer 15

All of western cad now considered endemic (maybe not Vancouver island), also in s. ontario
prevalence 30-70% in coyotes, 30% in foxes, 13% in wolves

Question 16

What is the life cycle of echinococcus multiocularis?

Answer 16

PPP 35 days
DH: fox, coyote, wolf, dog, (cat) > sheds infective eggs > develops 2-4 mo in IH of lemming, vole, deer mouse or other IH > ingested by DH
dogs may also eat the eggs and it will live in their liver

Question 17

What are the larval stages of echinococcus spp?

Answer 17

Cystic hydatid - many protoscolices free in single chambered fluid-filled cyst
Alveolar hydatid - many protoscolices free in multichambered fluid-filled cysts

Question 18

How do we diagnose canine alveolar echinococcosis?

Answer 18

Suspicion: medical imaging, liver mass in yg dog - ddx neoplasia, granuloma, other causes of cysts
Suggestive: serology, histopathology - protoscolices only present in about 1/3rd of dogs, periodic acid-schiff (PAS) stain to detect membrane, calcareous corpuscles, potential for misdiagnosis w/ other larval cestodes
Definitive: immunohistochemistry, PCR - abdominocentesis fluid, aspirated cyst contents, biopsy, surgical resection

Question 19

What are the risk factors of alveolar echinococcosis?

Answer 19

at least 35 cases of dogs in CAD since 2009, 6+ in SK, 15+ in AB
comes from contact w/ wildlife, esp coyotes and foxes bc habitat overlap, 70% of coyotes in a study w/ European strain of E. multi
Use of off leash areas and coprophagic dogs

Question 20

How can we manage canine AE?

Answer 20

collect fecal sample for float and/or fecal PCR
treat w/ adult cestocide (initially) - praziquantel at 5mg/kg daily for 2 days
Trat w/ larval cestocide (long-term/life-long) albendazole (larval cestocide) @ 10mg/kg daily
Surgical debulking/resection if clinically indicated
advise owner to consult health care provider
poor prognostic indicators: late detection, significant abdominal effusion, metastases

Question 21

How can we control echinococcus in the DH (dog)?

Answer 21

GOAL: halt enviro contam w/ immediately infective, highly resistant eggs - resistant to most chemicals but are killed by heat, drying and freezing below -80C
CONTROL: prevent access to IH (freeze or cook offal)
Tx bc of public health considerations
Praziquantel has high efficacy against adults
dogs that are free roaming, hunting, scavenging or eating raw meat are most susceptible. Treat prophylactically, year round or every 4-6wks - know positive (eggs may shed for 3 days post tx),

Question 22

What are the larval stages of cyclophyllid cestodes?

Answer 22

Cystericercoid - single protoscolex, no cyst, in an arthropod
Cystericercus - single protoscolex, fluid-filled cyst
Coenurus - many (10’s) protoscolices attached to a wall of a fluid filled cyst
Strobilocercus - single minature adult, no cyst
Cystic hydatid (many (1000’s) protoscolices free in fluid-filled cyst
Alveolar Hydatid - many in multichambered fluid filled cysts