Veterinary Parasitology CH6 - Tapeworms of Domestic Animals and Humans

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Study material for Chapter 6 of Diagnostic Parasitology for Veterinary Technicians. For class BIO225 at MWCC.

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29 Terms

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Hymenolepis nana, Hymenolepis diminuta

“Dwarf tapeworm” (nana), “Rodent tapeworm” (diminuta)

  • Hymenolepis nana: 1 mm by 25-40mm​

  • Hymenolepis diminuta: 3 mm by 20-60 mm

  • Affects: Mice, rats, gerbils, hamsters (definitive) dogs and humans (H. nana more common - incidental)​

  • Adults: small intestine​

  • Found: Worldwide​

  • Cause of infection: Ingestion of infective fleas, beetle, cockroach (H. diminuta) which is intermediate host​; Ingestion of infective egg or autoinfection (H. nana) no intermediate host

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Hymenolepis nana life cycle

  1. Eggs pass in feces — direct life cycle – only tapeworm that does not need intermediate host​

  2. Swallowed by host, hexacanth enters villus of small intestine​

  3. Matures into nontailed cysticercoid​

  4. Moves back to lumen, attaches to lining and matures to adult stage

<ol><li><p>Eggs pass in feces — direct life cycle – only tapeworm that does not need intermediate host​</p></li><li><p>Swallowed by host, hexacanth enters villus of small intestine​</p></li><li><p>Matures into nontailed cysticercoid​</p></li><li><p>Moves back to lumen, attaches to lining and matures to adult stage</p></li></ol><p></p>
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Hymenolepis diminuta life cycle

  1. Eggs pass in feces​

  2. Ingested by arthropod intermediate host​

  3. Hexacanth embryo matures into tailed cysticercoid​

  4. Attaches to lining of small intestine and matures into adults

<ol><li><p>Eggs pass in feces​</p></li><li><p>Ingested by arthropod intermediate host​</p></li><li><p>Hexacanth embryo matures into tailed cysticercoid​</p></li><li><p>Attaches to lining of small intestine and matures into adults</p></li></ol><p></p>
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Hymenolepis sp. eggs

  • Eggs are detectable in fecal floatation, but shed intermittently​

  • Proglottids do not float​

<ul><li><p>    Eggs are detectable in fecal floatation, but shed intermittently​</p></li><li><p>    Proglottids do not float​</p></li></ul><p></p>
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Moniezia expansa

“Ruminant tapeworm”

  • Affects: Cattle, sheep and goats (Moniezia benedini in cattle only)​

  • Found in: Worldwide

  • Adult in small intestine​

  • Cause of infection: Ingestion of infected grain​

  • Much larger than Hymenolepis (up 1.6 cm by 6m)

  • Unarmed scolex​

  • Short, wide proglottids​

  • Unique eggs with square (M. benedini) or triangular (M. expansa) shells​

  • Three-layered egg shell, inner-most is pyriform apparatus—pear shaped​

  • Prepatent period: 40 days​

  • Eggs seen on fecal flotation

<p>“Ruminant tapeworm”</p><ul><li><p>Affects: Cattle, sheep and goats (Moniezia benedini in cattle only)​</p></li><li><p>Found in: Worldwide</p></li><li><p>Adult in small intestine​</p></li><li><p>Cause of infection: Ingestion of infected grain​</p></li><li><p>Much larger than Hymenolepis (up 1.6 cm by 6m)</p></li><li><p>Unarmed scolex​</p></li><li><p>Short, wide proglottids​</p></li><li><p>Unique eggs with square (M. benedini) or triangular (M. expansa) shells​</p></li><li><p>Three-layered egg shell, inner-most is pyriform apparatus—pear shaped​</p></li><li><p>Prepatent period: 40 days​</p></li><li><p>Eggs seen on fecal flotation</p></li></ul><p></p>
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Moniezia metacestode stage

  • Proglottids and eggs in feces of infected ruminants​

  • Cysticercoid found inside oribatid grain mites that have ingested hexacanth embryo​

  • Ruminants infected by eating infected grain​

  • Each cysticercoid forms one adult​

  • Large numbers of adults can block intestines, especially in young animals​

  • Pasture rotation as well as management of grain mites can help with reinfection rates

<ul><li><p>Proglottids and eggs in feces of infected ruminants​</p></li><li><p>Cysticercoid found inside oribatid grain mites that have ingested hexacanth embryo​</p></li><li><p>Ruminants infected by eating infected grain​</p></li><li><p>Each cysticercoid forms one adult​</p></li><li><p>Large numbers of adults can block intestines, especially in young animals​</p></li><li><p>Pasture rotation as well as management of grain mites can help with reinfection rates</p></li></ul><p></p>
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Thysanosoma actinoides

  • Affects: Sheep, goats, cattle​

  • Adults in lumen of bile duct, pancreatic duct, small intestine – can cause obstructions​

  • Intermediate host: unknown, possibly psocids (“booklice” that feed off mold, lichen, grains and wallpaper and book- binding glue)​

  • Derivation: “fringed body”– unique fringe on the posterior half of each proglottid​

  • Unarmed scolex, form egg packets (6-12), no pyriform apparatus

<ul><li><p>Affects: Sheep, goats, cattle​</p></li><li><p>Adults in lumen of bile duct, pancreatic duct, small intestine – can cause obstructions​</p></li><li><p>Intermediate host: unknown, possibly psocids (“booklice” that feed off mold, lichen, grains and wallpaper and book- binding glue)​</p></li><li><p>Derivation: “fringed body”– unique fringe on the posterior half of each proglottid​</p></li><li><p>Unarmed scolex, form egg packets (6-12), no pyriform apparatus</p></li></ul><p></p>
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Taenia saginata (adult), Cysticercus bovis (larval stage)

“Beef tapeworm”

  • Adult: small intestine​

  • Found: Worldwide​

  • Definitive host: Human​

  • Cause of infection: Ingestion of raw or undercooked intermediate host: beef cattle​

  • Only member of Taenia with unarmed scolex, 14-32 branches of uterus in gravid

<p>“Beef tapeworm”</p><ul><li><p>Adult: small intestine​</p></li><li><p>Found: Worldwide​</p></li><li><p>Definitive host: Human​</p></li><li><p>Cause of infection: Ingestion of raw or undercooked intermediate host: beef cattle​</p></li><li><p>Only member of Taenia with unarmed scolex, 14-32 branches of uterus in gravid</p></li></ul><p></p>
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Taenia solium (adult), Cysticercus cellulosae (larval stage)

  • “Pork tapeworm”

  • Adult: small intestine​

  • Found in: Mostly underdeveloped countries - Latin America, India, Africa, Far East​

  • Definitive host: human​

  • Cause of infection: Ingestion of undercooked intermediate host: pigs​

  • Armed scolex, 7-16 branches of uterus in gravid​

  • Can develop cysticercus in human muscle, brain, eye, spinal cord

<ul><li><p>“Pork tapeworm”</p></li><li><p>Adult: small intestine​</p></li><li><p>Found in: Mostly underdeveloped countries - Latin America, India, Africa, Far East​</p></li><li><p>Definitive host: human​</p></li><li><p>Cause of infection: Ingestion of undercooked intermediate host: pigs​</p></li><li><p>Armed scolex, 7-16 branches of uterus in gravid​</p></li><li><p>Can develop cysticercus in human muscle, brain, eye, spinal cord</p></li></ul><p></p>
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Taenia hydatigena (adult), Cysticercus tenuicollis (larval form)

“Canine/dog bladder worm”

  • Affects: Dogs, adults in small intestine

  • Intermediate host: cattle, sheep, goats​

  • Found in: Worldwide​

  • Cause of infection: Ingestion of omentum of ruminants with golf-ball size cysticercus (not pathogenic to ruminants)​

  • Armed scolex, proglottids have single lateral genital pore​

  • Eggs can be seen in fecal flotation

<p>“Canine/dog bladder worm”</p><ul><li><p>Affects: Dogs, adults in small intestine</p></li><li><p>Intermediate host: cattle, sheep, goats​</p></li><li><p>Found in: Worldwide​</p></li><li><p>Cause of infection: Ingestion of omentum of ruminants with golf-ball size cysticercus (not pathogenic to ruminants)​</p></li><li><p>Armed scolex, proglottids have single lateral genital pore​</p></li><li><p>Eggs can be seen in fecal flotation</p></li></ul><p></p>
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Anoplocephala sp.

  • A. perfoliata, A. magna, Paranoplocepha mamillana​

  • Found in: Worldwide​

  • Intermediate host: Grain mites​

  • Unarmed scolex

  • Cause of infection: Ingestion of mites​

  • Unique morphology: unarmed oblong scolex, two round lappets behind each of the four suckers, only one pair of reproductive organs per glottid​

  • Pyriform apparatus in egg with one or more flattened sides

<ul><li><p>A. perfoliata, A. magna, Paranoplocepha mamillana​</p></li><li><p>Found in: Worldwide​</p></li><li><p>Intermediate host: Grain mites​</p></li><li><p>Unarmed scolex</p></li><li><p>Cause of infection: Ingestion of mites​</p></li><li><p>Unique morphology: unarmed oblong scolex, two round lappets behind each of the four suckers, only one pair of reproductive organs per glottid​</p></li><li><p>Pyriform apparatus in egg with one or more flattened sides</p></li></ul><p></p>
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Dipylidium caninum

“Double pore” or “cucumber seed tapeworm”

  • Most common tapeworm of dogs and cats​

  • Affects: Dogs and cats​

  • Intermediate host: fleas​

  • Cause of infection: Ingestion of fleas​

  • 50 cm long​

  • Long proboscis on armed scolex​

  • Gravid proglottids can be motile when shed in feces, coat hair, bedding

  • Each gravid proglottid contains thousands of egg packets​

  • 20-30 eggs per packet, each with hexacanth embryo inside​

  • Prepatent period: 14-21 days

<p>“Double pore” or “cucumber seed tapeworm”</p><ul><li><p>Most common tapeworm of dogs and cats​</p></li><li><p>Affects: Dogs and cats​</p></li><li><p>Intermediate host: fleas​</p></li><li><p>Cause of infection: Ingestion of fleas​</p></li><li><p>50 cm long​</p></li><li><p>Long proboscis on armed scolex​</p></li><li><p>Gravid proglottids can be motile when shed in feces, coat hair, bedding</p></li><li><p>Each gravid proglottid contains thousands of egg packets​</p></li><li><p>20-30 eggs per packet, each with hexacanth embryo inside​</p></li><li><p>Prepatent period: 14-21 days</p></li></ul><p></p>
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Dipylidium caninum life cycle and prevention

  • Metacestode stage is cysticercoid in intermediate host: flea​

  • Larval fleas ingest hexacanth embryos​

  • Dogs and cats ingest the infected fleas​

  • Children are most likely humans to ingest fleas and get zoonotic infection​

  • Must include good flea control in order to prevent reinfestation​

  • Egg packets found in fecal flotation​

  • Proglottids found in gross feces

<ul><li><p>Metacestode stage is cysticercoid in intermediate host: flea​</p></li><li><p>Larval fleas ingest hexacanth embryos​</p></li><li><p>Dogs and cats ingest the infected fleas​</p></li><li><p>Children are most likely humans to ingest fleas and get zoonotic infection​</p></li><li><p>Must include good flea control in order to prevent reinfestation​</p></li><li><p>Egg packets found in fecal flotation​</p></li><li><p>Proglottids found in gross feces</p></li></ul><p></p>
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Taenia sp.

  • Affects: Dog​s

  • Adults in small intestine​

  • Intermediate hosts: Rabbits and hares (T. pisiformis), ruminants (T. hydatigena), sheep (T. ovis)​

  • Cause of infection: Ingestion of intermediate host​

  • 1-2 cm (T. ovis) to 200 cm (T. pisiformis) to 500 cm (T. hydatigena)​

  • Armed scolex, motile gravid proglottids– if found in feces, hydrate​ in saline on slide to see eggs inside​

  • Single lateral pore

  • T. pisiformis has pea sized cysticercus, attached to greater omentum of rabbit​

  • T. hydatigena has ping pong ball sized cysticercus, attached to greater omentum of ruminant​

  • T. ovis has cysticercus found in muscle of sheep ​

  • Preventing dogs and cats from eating viscera or musculature of intermediate hosts is best way to prevent Taenia infections

<ul><li><p>Affects: Dog​s</p></li><li><p>Adults in small intestine​</p></li><li><p>Intermediate hosts: Rabbits and hares (T. pisiformis), ruminants (T. hydatigena), sheep (T. ovis)​</p></li><li><p>Cause of infection: Ingestion of intermediate host​</p></li><li><p>1-2 cm (T. ovis) to 200 cm (T. pisiformis) to 500 cm (T. hydatigena)​</p></li><li><p>Armed scolex, motile gravid proglottids– if found in feces, hydrate​ in saline on slide to see eggs inside​</p></li><li><p>Single lateral pore</p></li><li><p>T. pisiformis has pea sized cysticercus, attached to greater omentum of rabbit​</p></li><li><p>T. hydatigena has ping pong ball sized cysticercus, attached to greater omentum of ruminant​</p></li><li><p>T. ovis has cysticercus found in muscle of sheep ​</p></li><li><p>Preventing dogs and cats from eating viscera or musculature of intermediate hosts is best way to prevent Taenia infections</p></li></ul><p></p>
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Taenia taeniaeformis (adult), Cysticercus fasciolaris (larval form)

  • Affects: Cats​

  • Intermediate host: Rats and mice​

  • Found in: Worldwide​

  • Cause of infection: Ingestion of rats and mice​

  • 60 cm long​

  • Armed scolex, bell shaped proglottids, taeniid egg

<ul><li><p>Affects: Cats​</p></li><li><p>Intermediate host: Rats and mice​</p></li><li><p>Found in: Worldwide​</p></li><li><p>Cause of infection: Ingestion of rats and mice​</p></li><li><p>60 cm long​</p></li><li><p>Armed scolex, bell shaped proglottids, taeniid egg</p></li></ul><p></p>
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Taenia taeniaeformis life cycle

Unique in that larval stage is strobilocercus​

  1. Rodents ingest hexacanth eggs from cat feces, develop into cysticercus inside liver for 42 days​

  2. On day 42, cysticercus changes shape into strobilocercus with scolex and long neck attached to bladder (Cysticercus fasciolaris)​

  3. Cat infected by eating rat or mouse liver​

  4. Scolex attaches to cat intestine

<p>Unique in that larval stage is strobilocercus​</p><ol><li><p>Rodents ingest hexacanth eggs from cat feces, develop into cysticercus inside liver for 42 days​</p></li><li><p>On day 42, cysticercus changes shape into strobilocercus with scolex and long neck attached to bladder (Cysticercus fasciolaris)​</p></li><li><p>Cat infected by eating rat or mouse liver​</p></li><li><p>Scolex attaches to cat intestine</p></li></ol><p></p>
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Multiceps sp.

“Many headed worm”

  • Affects: Dogs, not zoonotic​

  • Adult in small intestine​

  • Intermediate host: Sheep (M. multiceps) or rabbit (M. serialis)​

  • 40 to 100cm long​

  • Double row armed scolex, taeniid eggs

<p>“Many headed worm”</p><ul><li><p>Affects: Dogs, not zoonotic​</p></li><li><p>Adult in small intestine​</p></li><li><p>Intermediate host: Sheep (M. multiceps) or rabbit (M. serialis)​</p></li><li><p>40 to 100cm long​</p></li><li><p>Double row armed scolex, taeniid eggs</p></li></ul><p></p>
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Multiceps sp. metacestode stage

  • Forms coenurus that is found in sheep or rabbit intermediate host​

  • Coenurus cerebralis (M. multiceps) or Coenurus serialis (M. serialis)​

  • Single large bladder with several scolices attached to the wall​

  • Unique in that many tapeworms mature from each coenurus, one for each scolex​

  • In sheep, hexacanth embryos are ingested and larvae (5cm) migrate to nervous system (brain or spinal cord) and can produce neurological symptoms in infected sheep​

  • Dogs infected by ingesting sheep parts​

  • In rabbits, hexacanth embryos are ingested in dog feces, hatch and migrate into subcutaneous tissues which can interfere with movement, slow rabbits more likely to be caught and eaten by dogs

<ul><li><p>Forms coenurus that is found in sheep or rabbit intermediate host​</p></li><li><p>Coenurus cerebralis (M. multiceps) or Coenurus serialis (M. serialis)​</p></li><li><p>Single large bladder with several scolices attached to the wall​</p></li><li><p>Unique in that many tapeworms mature from each coenurus, one for each scolex​</p></li><li><p>In sheep, hexacanth embryos are ingested and larvae (5cm) migrate to nervous system (brain or spinal cord) and can produce neurological symptoms in infected sheep​</p></li><li><p>Dogs infected by ingesting sheep parts​</p></li><li><p>In rabbits, hexacanth embryos are ingested in dog feces, hatch and migrate into subcutaneous tissues which can interfere with movement, slow rabbits more likely to be caught and eaten by dogs</p></li></ul><p></p>
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Echinococcus granulosus (dogs) and Echinococcus multilocularis (cats)

“Spiny berry”

  • Intermediate host: Sheep, cattle, herbivores (E. granulosus), rats, mice and voles (E. multilocularis), ​

  • Both are highly zoonotic ​

  • Cause of infection: Ingestion of intermediate host​

  • Form unilocular (E. granulosus) or multilocular (E. multilocularis) hydatid cysts​

  • Adults are tiny: 1 to 7mm in length with only three proglottids: 1 immature, 1 mature, 1 gravid​

  • Very difficult to diagnose as gravids are seen in feces, adults never get to numbers that cause obstruction

<p>“Spiny berry”</p><ul><li><p>Intermediate host: Sheep, cattle, herbivores (E. granulosus), rats, mice and voles (E. multilocularis), ​</p></li><li><p>Both are highly zoonotic ​</p></li><li><p>Cause of infection: Ingestion of intermediate host​</p></li><li><p>Form unilocular (E. granulosus) or multilocular (E. multilocularis) hydatid cysts​</p></li><li><p>Adults are tiny: 1 to 7mm in length with only three proglottids: 1 immature, 1 mature, 1 gravid​</p></li><li><p>Very difficult to diagnose as gravids are seen in feces, adults never get to numbers that cause obstruction </p></li></ul><p></p>
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Diagnosis of Echinococcus

  • Can find adults in intestinal tract at necropsy​

  • Suspected infections can be diagnosed by purging animal of all feces using arecoline hydrobromide​

  • All feces should be handled with caution using gloves and incinerated​

  • Current ELISA tests for Echinococcus available​

  • Cases in dogs, cats or intermediate hosts must be reported to state and federal public health officials​

  • Taeniid eggs similar to Taenia and Multiceps sp.​

<ul><li><p>Can find adults in intestinal tract at necropsy​</p></li><li><p>Suspected infections can be diagnosed by purging animal of all feces using arecoline hydrobromide​</p></li><li><p>All feces should be handled with caution using gloves and incinerated​</p></li><li><p>Current ELISA tests for Echinococcus available​</p></li><li><p>Cases in dogs, cats or intermediate hosts must be reported to state and federal public health officials​</p></li><li><p>Taeniid eggs similar to Taenia and Multiceps sp.​</p></li></ul><p></p>
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Echinococcus metacestode

  • Larval stage is hydatid cyst​

  • E. granulosus forms unilocular cysts within liver, lung, other organs of ruminant

(Thick cyst wall, thin germinal membrane​; “Brood capsules” contain protoscolices that bud from germinal membrane​; Each protoscolex forms one adult worm)

  • E. multilocularis forms multilocular or alveolar cysts within liver, lungs of rodents

(No thick wall, grapelike cysts that are very invasive, replacing normal tissue almost like cancer​; Thin germinal membrane​; “Brood capsules” with protoscolices bud from membrane​; Praziquantel can treat adult Echinococcus but will not kill cyst stage)

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Mesocestoides sp.

  • Affects: Dogs, cats, other carnivores​

  • 12cm to 2m in length​

  • Oblong scolex, four acetabula, unarmed​

  • Only true tapeworm with two intermediate hosts

<ul><li><p>Affects: Dogs, cats, other carnivores​</p></li><li><p>12cm to 2m in length​</p></li><li><p>Oblong scolex, four acetabula, unarmed​</p></li><li><p>Only true tapeworm with two intermediate hosts</p></li></ul><p></p>
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Mesocestoides sp. metacestode stage

  • If ingested by oribatid mite, develops into cysticercoid inside mite ​

  • If cysticercoid ingested by mouse or reptile, develops into tetrathyridium which can multiply asexually to make large numbers that can infect dogs, cats​

  • Tetrathyridia multiply heavily in intermediate host, mostly in serous cavities like peritoneum or liver causing large increase in girth​

  • When ingested by definitive host, tetrathyridium develop into adults in small intestine

<ul><li><p>If ingested by oribatid mite, develops into cysticercoid  inside mite ​</p></li><li><p>If cysticercoid ingested by mouse or reptile, develops into tetrathyridium which can multiply asexually to make large numbers that can infect dogs, cats​</p></li><li><p>Tetrathyridia multiply heavily in intermediate host, mostly in serous cavities like peritoneum or liver causing large increase in girth​</p></li><li><p>When ingested by definitive host, tetrathyridium develop into adults in small intestine</p></li></ul><p></p>
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Pseudotapeworms Cotyloda

  • Look similar to true tapeworms but have centrally located reproductive organs​

  • Unembryonated operculated eggs (almost identical to trematodes)​

  • Most release eggs directly from uterus passed in feces of definitive host​

  • Sometimes short chains of proglottids are released​

  • No acetabula or rostellum but two slitlike organs called bothria

<ul><li><p>Look similar to true tapeworms but have centrally located reproductive organs​</p></li><li><p>Unembryonated operculated eggs (almost identical to trematodes)​</p></li><li><p>Most release eggs directly from uterus passed in feces of definitive host​</p></li><li><p>Sometimes short chains of proglottids are released​</p></li><li><p>No acetabula or rostellum but two slitlike organs called bothria</p></li></ul><p></p>
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Pseudotapeworms Cotyloda life cycles

  • All use two intermediate hosts​

  • Eggs that come into contact with water release ciliated hexacanth embryo called coracidium​

  • Swims in water, ingested by microscopic crustacean and develops into procercoid​

  • Then ingested by fish or amphibian, matures in muscle into metacestode larva called plerocercoid or sparganum​

  • Definitive host eats intermediate host to become infected

<ul><li><p>All use two intermediate hosts​</p></li><li><p>Eggs that come into contact with water release ciliated hexacanth embryo called coracidium​</p></li><li><p>Swims in water, ingested by microscopic crustacean and develops into procercoid​</p></li><li><p>Then ingested by fish or amphibian, matures in muscle into metacestode larva called plerocercoid or sparganum​</p></li><li><p>Definitive host eats intermediate host to become infected</p></li></ul><p></p>
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Spirometra sp.

“Zipper tapeworm” (due to mature proglottids pulling apart or unzipping)

  • Affects: Dogs and cats​

  • Found in: North and South America, Far East, Australia, most prevalent in Florida and Gulf Coast​

  • Adults in small intestine​

  • Intermediate host: crustacean, then fish or frog​

  • Rare to release gravid proglottids

<p>“Zipper tapeworm” (due to mature proglottids pulling apart or unzipping)</p><ul><li><p>Affects: Dogs and cats​</p></li><li><p>Found in: North and South America, Far East, Australia, most prevalent in Florida and Gulf Coast​</p></li><li><p>Adults in small intestine​</p></li><li><p>Intermediate host: crustacean, then fish or frog​</p></li><li><p>Rare to release gravid proglottids</p></li></ul><p></p>
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Sparganosis

knowt flashcard image
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Spirometra sp. metacestode stage

  • Sparganum larval stage, solid-body with slit-like mouthparts​

  • Found in muscle of intermediate host

<ul><li><p>Sparganum larval stage, solid-body with slit-like mouthparts​</p></li><li><p>Found in muscle of intermediate host</p></li></ul><p></p>
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Diphyllobothrium latum

  • “Double leaf” or “Broad fish tapeworm”

  • Affects: Dogs, cats, humans​

  • Adults in small intestine​

  • Intermediate host: crustacean, then fish​

  • Found in: Scandinavia, Ukraine, N. America​

  • 2m to 12m long​

  • Four acetabula and two bothria​

  • Can cause pernicious anemia in host due to B12 absorption, gravids detach in small chains​

  • Largest human tapeworm

<ul><li><p>“Double leaf” or “Broad fish tapeworm”</p></li><li><p>Affects: Dogs, cats, humans​</p></li><li><p>Adults in small intestine​</p></li><li><p>Intermediate host: crustacean, then fish​</p></li><li><p>Found in: Scandinavia, Ukraine, N. America​</p></li><li><p>2m to 12m long​</p></li><li><p>Four acetabula and two bothria​</p></li><li><p>Can cause pernicious anemia in host due to B12 absorption, gravids detach in small chains​</p></li><li><p>Largest human tapeworm</p></li></ul><p></p>