cestoda II (tapeworms)

cyclophyllidean cestode general features

• very common; most important tapeworms in vet med

• adults → infect intestine of definitive host

• metacestodes → major source of pathology

• eggs vary in shape and size; larvated with hooks

taeniasis

• infection of adult taenia spp. in intestines of definitive host

• infective stage is a cysticercus

cysticercosis

• infection of metacestodes in various tissues in intermediate host

• infective stage is an egg with oncosphere

taenia pisiformis definitive host

dog

taenia pisiformis intermediate host

rabbit, hare (peritoneum, other)

taenia transmission

ingestion of intermediate host infected with cysticerci

taenia taeniaeformis definitive host

cat

taenia taeniaeformis intermediate host

rodents (liver)

taeniasis pathology

• very common

• causes little disease (asymptomatic) unless in large numbers

taeniasis diagnostic stage

eggs/proglottids in feces

taeniasis treatment

• praziquantel or other anthelmintics

• avoid ingestion of cysticerci in intermediate hosts

  • humans: cooking/freezing meat; meat inspection & surveillance

  • cattle/swine: avoid egg contamination

cysticercosis pathology

• can be pathogenic depending on larval species and intensity (e.g. T. multiceps in CNS)

• economic importance

cysticercosis diagnostics

• clinical signs (depends on location); necropsy/slaughter

• difficult to diagnose

cysticercosis treatment

• no effective treatment → need to prevent

  • drugs not effective against larvae

• treatment could lead to anaphylactic shock

  • strong immune response after killing off larvae

taenia saginata definitive host

humans ONLY

taenia saginata intermediate host

cattle (muscle; cysticercus)

taenia saginata pathology

• little pathology in human infections; heavier infection can cause GI disturbance

• little pathology in cattle

• economic importance → condemnation/down-grading of meat

taenia solium definitive host

humans ONLY (adult worms)

taenia solium intermediate host

swine, human (embedded larval stage in muscle; other tissues; cysticercus)

taenia solium pathology

• adult worm infection

  • little pathology in human infections; heavier infection can cause GI disturbance

• metacestode infections

  • swine: economic impact

  • human cysticercosis: serious → can end up in brain (acquired epilepsy)

taenia solium diagnostics

• cysticercosis: serology, imaging

• proglottids or eggs in feces

taenia solium treatment (cysticercosis)

• difficult, inflammation & allergic reactions

• avoid ingestion of eggs

hydatid disease

disease caused by asexual reproduction of metacestodes (hydatid cyst) in intermediate hosts (mammals, including humans)

unilocular cyst

one big cyst with smaller cysts inside → daughter cyst bud off within original cyst

multilocular cyst

numerous daughter cysts bud off original cyst → can spread around body

echinococcus granulosus definitive host

canids

echinococcus granulosus intermediate hosts

mammals: sheep (common), cattle, swine, humans

echinococcus multilocularis definitive host

canids/felids

echinococcus multilocularis intermediate hosts

rodents (mice), humans; multilocular cyst particularly affects liver

echinococcus diagnotics

• serology, imaging of cysts

• diagnostic stage: eggs → PCR or antigen ELISA

echinococcus treatment

• praziquantel (adult worms)

• hydatid disease: albendazole, surgical removal of unilocular cysts

• feces disposal; avoid contacting/ingesting eggs

dipylidium caninum definitive hosts

dogs and cats

dipylidium caninum intermediate host

fleas/lice (cysticercoid)

dipylidium caninum life cycle

egg packets (larvated oncosphere)/proglottids passed in feces → ingested by flea larvae → cysticercoid in fleas/lice → intermediate host infected with cysticercoid ingested by definitive host

dipylidiasis pathology

little pathology with adult worm infections; incidental finding

dipylidiasis diagnostics

• eggs/egg packets → fecal floatation

• proglottids in fresh feces

dipylidiasis treatment

• praziquantel, others effective

• prevent flea infestation

• zoonotic → important to treat dog or cat

mesocestoides intermediate hosts (2)

• 1st = mite (cystercercoid)

• 2nd = vertebrates, including dogs (many different 2nd vectors)

mesocestoides life cycle

egg passed in feces → hatches/ingested by mite (cysticercoid) → mite ingested by 2nd intermediate host (vertebrate) → 2nd intermediate host ingested by definitive host → adult worms in intestine

mesocestoides reproduction

• asexual reproduction in peritoneal body cavity in second intermediate host

• budding new adults from scolex region in definitive host

mesocestoides pathology

not common, but infections can lead to serious disease due to asexual reproduction of both larval and adult worm stages in dogs

mesocestoides diagnosis

• thin shelled eggs with oncosphere

• motile gravid proglottids with parauterine organ

mesocestoides treatment

• praziquantel

• note: must achieve 100% elimination of adults or infection can reoccur due to asexual development

moniezia definitive host

cattle, sheep, goats (large and small ruminants)

moniezia intermediate host

oribatid mites (cysticercoid)

moniezia diagnostic stage

eggs in feces; contains pyriform apparatus (shaped like bowling pin/ice cream cone)

moniezia pathology

• very common worldwide

• responsible for subclinical parasitism = production loss

moniezia treatment

strategic deworming

anoplocephala perfoliata definitive host

horse → ileocecal orifice in intestines

anoplocephala perfoliata intermediate host

oribatid mites (cysticercoid)

anoplocephala perfoliata diagnostic stage

eggs in feces; contains pyriform apparatus

anoplocephala perfoliata treatment

praziquantel, pyrantel pamoate, strategic deworming