Download Platyhelminths - University of East London

Platyhelminths 2
Cestoidea
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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Cestoidea
Tissue & Intestinal
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Tissue cestodes
(extra-intestinal)
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Echinococcus grqnulosa •
Echinococcus multilocularis•
Multiceps spp
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Spirometra mansonoides •
Diphyllobothrium spp
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Taenia solium
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Disease
Hydatid disease (6k)
Hydatid disease (rare)
Coenurosis (rare)
Sparganosis (rare)
Sparganosis (?)
Cysticercosis (?)
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Cestoidea
Tissue & Intestinal
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Intestinal Cestodes
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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 Cestodes
Tapeworms
 Attached via a scolex to mucosa (small intestine)
 Composed of proglottids forming a strobila
 Each proglottid contains male & female
reproductive organs
 Immature >> Mature >> 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 nana
Dwarf Tapeworm
 Intermediate host not required
• infection via intermediate insect host rare
• commonest tapeworm in UK and US (<1%)
 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 nana
Dwarf 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 nana
Dwarf 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 nana
Control
 World-wide incidence 4%
 Treatment usually Praziquantel previously
Niclosamide (both single oral dose)
 Health education
 Rodent reservoir?
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Taenia saginata
Beef 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 saginata
Beef 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 saginata
Beef Tapeworm
 Usually asymptomatic
• hunger pains, weight loss
• discomft & embarrassment at voiding
proglottids
 Diagnosis based on recover of gravid
proglottid (uterine branches >15)
 Praziquantel or niclosamide
 Health education
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Taenia solium
Pork Tapeworm
 Recognised since biblical times
 Risk of cysticercosis
 Evagination > 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
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 Less than 1000 proglottids
Taenia solium
Pork Tapeworm
 Usually asymptomatic similar to S.
saginata
• Low grade eosinophilia <15%
 Treatment
• praziquantel
• niclosamide
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Taenia solium
Cysticercosis
 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 solium
Cysticercosis
 Bladder worms upto 60ml in volume
(usually around 5 x 800 mm)
 Diagnosis
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surgical removal
X ray - calcified larvae
CT scan or MRI for brain lesions
Fine needle aspirate
Serology/PCR
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Taenia solium
Cysticercosis
 Treatment
• surgical removal
• praziquantel (15 day course)
– only treatment for cysticercus
• albendazol (8 day course)
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Tissue Cestodes
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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
Definitive host
Intermediate host
Egg production
Worm lives 2+ years
Cyst evaginates
Hatch - onchosphere
invades mucosa &
penetrates capillaries
Cysts form in liver & lungs
Secondary metastasis
20+ years
Secondary daughter cysts
bud in E. multilocularis
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Clinical Features
 Definitive Host
• usually asymptomatic
 Intermediate Host
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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)
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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
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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
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