parasitology quiz 3

true tapeworm

• have scolex

• genital pores located laterally on both sides

• mature eggs contain a hexacanth embryo

false tapeworm

• bothria

• genital pore located centrally

gravid

mature proglottid

small intestine

adult cestodes live in the ______ of host

cestode route of infection

definitive host ingesting an intermediate host containing metacestode

cestode life cycle

always indirect

Diplydium caninum

• flea tapeworm

• definitive hosts: dogs, cats, canids, felids, humans

• intermediate host: cat flea

Diplydium caninum

What is the most common tapeworm in North America?

Diplydium caninum life cycle

• egg packets ingested by fleas in environment

• PPP: 2-3 weeks

Dipylidium caninum clinical signs

• normally minimal

• GI blockage in heavy infections

• scooting

• emaciation

• abdominal discomfort

diagnosis of Dipylidium caninum

• ID on animal

• crush egg packets under microscope

• fecal antigen test

• fecal PCR

treatment of Dipylidium caninum

• Praziquantel or Epsiprantel for treatment of cestode infection

• Isoxazoline drugs for treatment of fleas

Taenia pisiformis

• definitive host: dog

• intermediate host: rabbit

• scolex has hooks

• rectangular proglottids

• cysticercus

Taenia taeniformis

• definitive host: cat

• intermediate host: rodents

• strobilocercus

Taenia lifecycle

• route of infection: ingestion of intermediate host with metacestode

• PPP: 2-3 months

Taenia clinical signs

• typically, no problems

• heavy infection: obstruction, impaction

• rarely can act as linear foreign bodies

Taenia diagnosis

• ID proglottids on animals

• crush between microscope slides to release egg

• dense eggs; will not float well

• fecal PCR (best way to confirm)

treatment of Taenia

• Fenbendazole (dogs: T. pisiformis)

• Praziquantel (dogs and cats)

• Epsiprantel (dogs and cats)

prevention/control of Taenia

• prevent predation

• rodent control

• keep intermediate hosts away from dog/cat feces

• not zoonotic

Uncommon Taenia species

• T. crassiceps

• T. multiceps

Echinococcus granulosis/Echinococcus canadensis

• definitive host: dogs and wild canids

• intermediate hosts: sheep, cervids, humans

• metacestode: unilocular hydatid cyst in liver, lungs

• common in Idaho, Washington, northern Cali

Echinococcus multilocularis

• definitive host: foxes, coyotes, dogs

• intermediate host: rodents, humans, dogs (rarely)

Echinococcus species

• very small

• cannot differentiate eggs from Taenia eggs

• metacestodes: unilocular hydatid cyst

Echinococcus granulosis life cycle

• indirect

• route of infection: ingestion of unilocular hydatid cyst

• PPP: 1-2 months

• pastoral/domestic cycle: dogs & sheep

• sylvatic (wildlife) cycle: wild caninds and cervids

Echinococcus multilocularis life cycle

• indirect

• rout of infection: ingest alveolar hydatid cycst

• normal sylvatic cycle: foxes and rodents

• PPP: 1-2 months

• rarely, dogs ingest eggs and become IH; alveolar hydatid disease

Echinococcus clinical signs

• no clinical signs in definitive host, but IH can have pressure necrosis, cysts, loss of organ function

Echinococcus diagnosis

• impossible to ID proglottids in feces

• fecal PCR best way to confirm

• cannot tell difference from Taenia egg

Echinococcus treatment

• Praziquantel or epsiprantel for adult worm in dogs and canids

• no treatment for cysts in IH

Echinococcus prevention/control

• clean up carnivore feces routinely

• prevent predation

• zoonotic implications: humans can serve as IH, hydatid cysts in liver, lungs, brain

Mesocestoides species

• definitive host: dogs, cats, other mammals

• 1st intermediate host: arthropod

• 2nd intermediate host: reptiles, amphibians, small mammals, birds (dogs can also)

• 4 suckers, no hooks

• medial genital pore with distinct parauterine organ

Mesocestoides metacestode

tetrathyridia (little cyst)

Mesocestoides life cycle

• indirect

• route of infection: ingestion of 2nd intermediate host with tetrathyridium

• eggs ingested by 1st IH

• PPP: 2-3 weeks

Mesocestoides clinical signs

• usually asymptomatic

• anorexia

• loose, mucoid stools with tapeworm segments

• peritoneal larval infection: abdominal distension, weight loss, vomiting, diarrhea

Mesocestoides diagnosis

• ID proglottids (small, parauterine organ)

• flotation unreliable

• radiographs: evidence of fluid

• overall rare in the US

Mesocestoides treatment

• adults: Praziquantel, guarded prognosis

• peritoneal form: surgical removal/lavage and fenbendazole

• zoonotic: humans can be DH but rare

Spirometra

• zipper tapeworm

• definitive host: dogs, cats, carnivores

• 1st intermediate host: copepod (aquatic)

• 2nd intermediate host: non-fish vertebrate (amphibians, reptiles, birds, mammals)

Dibothriocephalus

• broad fish tapeworm

• definitive host: dogs, cats, carnivores

• 1st intermediate host: copepod

• 2nd intermediate host: fish

Spirometra & Dibothriocephalus species

• large tapeworms

• proglottids wider than long with single medial genital pore

• scolex elongated

• eggs: smooth surface

Spirometra life cycle

• route of infection: ingestion of plerocercoid ion anything but fish

• eggs ingested by copepod

• 2nd IH ingests copepod

• PPP: 15-30 days

Dibothriocephalus life cycle

• ingestion of plerocercoid in fish

• eggs ingested by copepod

• copepod ingested by fish

• PPP: 40 days

Spirometra & Dibothriocephalus clinical signs

• diarrhea, weight loss

• vomiting

• Spirometra: sparganosis (2nd IH)

• Dibothriocephalus: vitamin B12 deficiency

diagnosis of Spirometra and Dibothriocephalus

• sedimentation

• Id adults in vomit, feces, or at necropsy

• Spirometra: Id plerocercoids

Spirometra & Dibothriocephalus treatment

• nothing approved in dogs/cats

• 5x praziquantel oral for 2 days

Spirometra prevention/control

• prevent predation

• do not feed raw frogs, snakes, etc. to pets

Dibothriocephalus prevention/control

• fence off aquatic areas

• do not feed raw fish to pets

Spirometra & Dibothriocephalus zoonosis

• spirometra: humans cannot be DH, but can be paratenic or 2nd IH

• Dibothriocephalus: humans can be DH by ingestion of raw fish, causes B12 deficiency