1. Platyhelminths 2 Cestoidea
David Humber

2. 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

3. Cestoidea Tissue & 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

4. Cestoidea Tissue & 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

5. 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

6. Tapeworms Hymenolepis nana Taenia saginata - Taenia solium
Dwarf tapeworm (upto 40mm - largely children)
Taenia saginata -
Beef tapeworm (upto 25m)
Taenia solium
Pork tapeworm (upto 7m)
World-wide distribution

7. 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

8. 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

9. 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)

10. Hymenolepis nana Control
World-wide incidence 4%
Treatment usually Praziquantel previously Niclosamide (both single oral dose)
Health education
Rodent reservoir?

11. 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)

12. 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)

13. 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

14. 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
Less than 1000 proglottids

15. Taenia solium Pork Tapeworm
Usually asymptomatic similar to S. saginata
Low grade eosinophilia <15%
Treatment
praziquantel
niclosamide

16. 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)

17. Taenia solium Cysticercosis
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

18. Taenia solium Cysticercosis
Treatment
surgical removal
praziquantel (15 day course)
only treatment for cysticercus
albendazol (8 day course)

19. Tissue Cestodes Taenia solium Echinococcus grqnulosa
Echinococcus multilocularis
Diphyllobothrium spp
Multiceps spp
Spirometra mansonoides

20. Echinococcosis - Hydatid disease
Echinococcus granulosa
worldwide
Echinococcus multilocularis
Europe, Russia, China, Canada
Echinococcus vegeli
Central & South America

21. Distribution

22. Hydatidosis Known since Hipporates 400BC
Most serious of the tapeworm infections

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

24. Lifecycle Definitive host Intermediate host
Egg production
Worm lives 2+ years
Cyst evaginates
Intermediate host
Hatch - onchosphere invades mucosa & penetrates capillaries
Cysts form in liver & lungs
Secondary metastasis
20+ years
Secondary daughter cysts bud in E. multilocularis

25. Clinical Features Definitive Host Intermediate 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

26. Diagnosis Parasitological Radiological (CT & MRI) & ultrasound
eosinophilia
palpation
Radiological (CT & MRI) & ultrasound
differente from tumor
Immunological
Skin test - Casoni test - 18% false +ves
Serology

27. Treatment & Control Surgery Praziquantel or albendazol
drainage + 5 mins 10% formalin
Praziquantel or albendazol
steroids to prevent inflammation
aspiration + 95% ethanol
Health education
sanitation - dogs cats raw meat

28. 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

29. 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

30. 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

31. 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

32. Sparganosis Some species of Diphylobothrium and Spirometra
larva invade

33. Nematode Infections

34. Nematodes Half million species 50% free living
animal & plant parasites
Animal
vertebrate & invertebrate hosts
infection by ingestion
penetration

35. 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

36. 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