Platyhelminths 2 Cestoidea

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Platyhelminths 2Cestoidea

• David Humber

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Cestodes - Tapeworms

• Endoparasites
• No mouth or alimentary tract
• Attachment organ - anterior
• Elongated body - divided into proglottids
• Adults in intestines of vertebrates
• Larval stages in 1 or 2 intermediate hosts

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CestoideaTissue Intestinal

• Disease
• Hydatid disease (6k)
• Hydatid disease (rare)
• Coenurosis (rare)
• Sparganosis (rare)
• Sparganosis (?)
• Cysticercosis (?)

• Tissue cestodes
• (extra-intestinal)
• Echinococcus grqnulosa
• Echinococcus multilocularis
• Multiceps spp
• Spirometra mansonoides
• Diphyllobothrium spp
• Taenia solium

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CestoideaTissue Intestinal

• Intestinal Cestodes
• Diphyllobothrium latum
• Taenia solium
• Taenia saginata
• Hymenolepis nana
• Hymenolepis diminuta
• Dipylidium canis

• Cases
• 16 million
• 5 million
• 76 million
• 36 million
• Rare
• Rare

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Intestinal CestodesTapeworms

• Attached via a scolex to mucosa (small intestine)
• Composed of proglottids forming a strobila
• Each proglottid contains male female
  reproductive organs
• Immature gtgt Mature gtgt Gravid

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Tapeworms

• Hymenolepis nana
• Dwarf tapeworm (upto 40mm - largely children)
• Taenia saginata -
• Beef tapeworm (upto 25m)
• Taenia solium
• Pork tapeworm (upto 7m)

World-wide distribution
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Hymenolepis nanaDwarf Tapeworm

• Intermediate host not required
• infection via intermediate insect host rare
• commonest tapeworm in UK and US (lt1)
• Eggs via oral-faecal route
• Hatch in stomach/small intestine
• Larvae (onchospheres) penetrate villi
• Develop into cysticercoid stage
• Migrate back into lumen

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Hymenolepis nanaDwarf Tapeworm

• Maturation 2-4 weeks
• Length dependent on parasitemia
• Scolex - 4 suckers short rostellum with hooks
• Eggs released by disintergration of terminal
  proglottids
• Eggs immediately infectious

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Hymenolepis nanaDwarf Tapeworm

• Often asymptomatic even with high worm burden
• headache, dizziness, anorexia, abdominal pain,
  diarrhea, low grade eosinophilia
• Heavy infections via auto infection (in
  intestine)
• Diagnosis by egg morphology (adults v rarely seen)

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Hymenolepis nanaControl

• World-wide incidence 4
• Treatment usually Praziquantel previously
  Niclosamide (both single oral dose)
• Health education
• Rodent reservoir?

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Taenia saginataBeef Tapeworm

• Commonest taenia infection (Ethiopia)
• Ingestion of raw or poorly cooked beef
• Larvz digested evaginates in small intestine
• Scolex 4 suckers no hooks
• Proglottids 1-2k (lateral unterine branches
  15-20)

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Taenia saginataBeef Tapeworm

• Motile proglottids crawl through anus during day
• Eggs identical to T. solium (viable upto 159
  days)
• Larvae (onchospheres) hatch in cattle intestine
• Migrate through villi via lymphatics/blood to
  striated muscle
• Develop into cysticerci (bladder worm)

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Taenia saginataBeef Tapeworm

• Usually asymptomatic
• hunger pains, weight loss
• discomft embarrassment at voiding proglottids
• Diagnosis based on recover of gravid proglottid
  (uterine branches gt15)
• Praziquantel or niclosamide
• Health education

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Taenia soliumPork Tapeworm

• Recognised since biblical times
• Risk of cysticercosis
• Evagination gt six hooked four suckers larva
  (onchophore) in small intestine
• Attaches to mucosa (penetrates in cysticercosis)
• Matures in 5-12 weeks
• Usually long lived (25 years) single worm
• Less than 1000 proglottids

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Taenia soliumPork Tapeworm

• Usually asymptomatic similar to S. saginata
• Low grade eosinophilia lt15
• Treatment
• praziquantel
• niclosamide

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Taenia soliumCysticercosis

• Onchospheres penetrate intestine (adult worm not
  usually found)
• Distributed via mesenteric venules
• Most organs including brain, eyes, sucutaneous
  and intramuscular
• Sometimes multiple organs (geographical
  variations)

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Taenia soliumCysticercosis

• Bladder worms upto 60ml in volume (usually around
  5 x 800 mm)
• Diagnosis
• surgical removal
• X ray - calcified larvae
• CT scan or MRI for brain lesions
• Fine needle aspirate
• Serology/PCR

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Taenia soliumCysticercosis

• Treatment
• surgical removal
• praziquantel (15 day course)
• only treatment for cysticercus
• albendazol (8 day course)

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Tissue Cestodes

• Taenia solium
• Echinococcus grqnulosa
• Echinococcus multilocularis
• Diphyllobothrium spp
• Multiceps spp
• Spirometra mansonoides

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Echinococcosis - Hydatid disease

• Echinococcus granulosa
• worldwide
• Echinococcus multilocularis
• Europe, Russia, China, Canada
• Echinococcus vegeli
• Central South America

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Distribution
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Hydatidosis

• Known since Hipporates 400BC
• Most serious of the tapeworm infections

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Hosts

• Definitive Host
• Canids felids
• 59 dogs in Istanbul (E.granulosa)
• Intermediate Host
• humans 60 species
• ungulate,marsupials, elephants,primates,
• rodents for E. multilocularis

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Lifecycle

• Intermediate host
• Hatch - onchosphere invades mucosa penetrates
  capillaries
• Cysts form in liver lungs
• Secondary metastasis
• 20 years
• Secondary daughter cysts bud in E. multilocularis

• Definitive host
• Egg production
• Worm lives 2 years
• Cyst evaginates

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Clinical Features

• Definitive Host
• usually asymptomatic
• Intermediate Host
• dependent on burden site
• usually single - 50 in liver, 3 brain (E.g)
• incubation 5 years
• 6-10 diagnosed cases fatal
• Eosinophilia in 25 cases

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Diagnosis

• Parasitological
• eosinophilia
• palpation
• Radiological (CT MRI) ultrasound
• differente from tumor
• Immunological
• Skin test - Casoni test - 18 false ves
• Serology

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Treatment Control

• Surgery
• drainage 5 mins 10 formalin
• Praziquantel or albendazol
• steroids to prevent inflammation
• aspiration 95 ethanol
• Health education
• sanitation - dogs cats raw meat

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Diphylobothrium - Sparganosis

• Diphylobothrium latum
• Broadfish tapeworm
• Definitive host
• humans/dogs/cats/pigs/bears/otters, seals etc
• First intermediate host
• Copepods
• Second intermediate host
• trout/salmon/perch/pike

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Intestinal infections

• Limited to fish eating areas
• raw or improperly cooked
• dumping untreated raw sewage
• Adult worms (upto 10m)
• attach to lining of intestine
• Ovoid operculated eggs released
• Eggs dormant in water (8-12 days)
• motile coracidium hatches ingested by freshwater
  copepod

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Intestinal infections

• Ciliated embryophore shed naked hexacanth larva
  attaches by hooks
• Bores through intestinal wall into haemocoel
• Hexacanth metamorphose into procercoid (14-18
  days) 500um in length

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Intestinal infection

• In fish procercoid penetrates intestinal wall
• migrates to muscles
• develops into plerocercoid (20-40mm) in
• 7-30 days with fully developed scolex
• In definitive host attaches to mucosa
• grows at 30 proglottids a day
• Full sexual maturity in 3-5 weeks

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Sparganosis

• Some species of Diphylobothrium and Spirometra
• larva invade

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Nematode Infections
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Nematodes

• Half million species
• 50 free living
• animal plant parasites
• Animal
• vertebrate invertebrate hosts
• infection by ingestion
• penetration

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Nematodes

• Generally elongated, cylindrical tapered at
  each end (99)
• fluid filled pseudocoelom logitudinal muscle only
• no vasculature or respiratory system
• usually sexual dimorphism (some parthenogenetic)
• males usually smaller than females
• most between 1mm and 150mm
• colourless translucent to opaque with an elastic
  curticle

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Ascaris

• Large intestinal round worm
• mouth with I dorsal 2 ventral lips
• female 40cm male 30cm
• Uterus of mature female 20 million eggs
• Sheds 200,000 golden brown ovoid eggs per day
• Eggs resistant to desiccation