1. Cestode (tapeworm,绦虫)

2. GENERAL INTRODUCTIONS
     Taxonomic position
Phylum platyhelminthes
Class Cestoda
Order Cyclophyllidae
Order Pseudophyllidae
    

3. MORPHOLOGICAL FEATURES
Flat and Segmented
Scolex-equipped with organs of attachment:
suckers, hooks, grooves
Neck - germinal portion
Strobila:
Proglottids
Immature proglottid
Mature proglottid
gravid proglottid

4. MORPHOLOGICAL FEATURES
Body wall: Tegument and
subtegument (syncytial layer);
no coelomic cavity
Monoecious
Digestive system: completely
degenerated

5. PHYSIOLOGY AND PATHOGENESIS
Surface absorption capabilities
Highly developed reproductive
functions
Anaerobic metabolism
All species are parasitic
Pathogenic stage may be adult or the
larva

6. LIFE CYCLE PATTERNS Spirometra mansoni – cause sparganosis
1. Pseudophyllidae type
Scolex provided 2 grooves - bothrium
Need two intermediate hosts
aquatic crustaceans
fish or other vertebrate animals
Life stages
eggcoracidium  procercoid plerocercoid(sparganum)
 adult worm
Spirometra mansoni – cause sparganosis
Diphilobothrium latum – accidental infection in humans
copepod

7. LIFE CYCLE PATTERNS 2. Cyclophyllidae type
Scolex provided 4 suckers sometimes supplemented with circular of hooks
Need one intermediate host only -- usually mammals
Life stages
egg hexacanth metacestode stage  adult worm.
Taenia solium
Teania saginata
Echinococcus granulosus
E. multilocularis
Hymenolepis spp

8. Larval stage of a cestode that develop in the intermediate host.
Metacestode stage
Larval stage of a cestode that develop in the intermediate host.
Cysticercus - Taenia spp.
Hydatid cyst - Echinococcus granulosus
Alveolar hydatid cyst - E. multilocularis
Cysticercoid - Hymenolepis spp.
Different species of cestode may have different types of metacestode stage

9. Important species Taenia solium Teania saginata
Echinococcus granulosus
Spirometra mansoni
Hymenolepis nana
Hymenolepis diminuta
Important species

10. Taenia solium (猪带绦虫) Taenia saginata (牛带绦虫)

11. Taenia solium GENERAL INTRODUCTION Worldwide distribution
Large tapeworm
Larval infection of Taenia solium may cause serious clinical disease ---CYSTICERCOSIS

12. Morphology Can be up to 2 to 4 meters long
It has a globular scolex with four suckers and 2 circular rows of hooks (rostellum)
The gravid proglottids are 5×10 mm with a 7-13 branched uterus
The eggs of T. solium and T. saginata are indistinguishable

13. scolex of T. solium.

14. Gravid proglottids of Taenia solium
Gravid proglottids of Taenia solium. Injection of India ink in the uterus allows visualization of the primary lateral branches. T. solium has branches on each side. Note the genital pores in mid-lateral position.
Taenia solium

15. eggs of Taenia solium and T. saginata
The eggs are rounded or subspherical, diameter µm, with a thick brown embryophore. Inside each egg is an embryonated oncosphere with 6 hooks. A complete egg always has the primary membrane (shell) that surrounds eggs.

16. Cysticercus

17. Life cycle of T.solium

18. Main points of the life cycle
Man is the only definitive host, but he can also be the intermediate host for T.solium
Pig is the important intermediate host for T.solium
Adult worm reside in the lumen of the upper part of small intestine
The infective stage to man are both egg/gravid proglottid and cysticercus for T.solium

19. A tapeworm larval cyst (cysticercus) is ingested with poorly cooked rice-like meat
The larva escapes the cyst and passes to the small intestine where it attaches to the mucosa by the scolex suckers
The proglottids develop as the worm matures in 3 to 4 months

20. Main points of the life cycle
The adult may live in the small intestine as long as 25 years and pass gravid proglottids with the feces
When eggs consumed by pigs in which they hatch and form cysticerci
T.solium eggs can also infect humans and cause cysticercosis (larval cysts in lung, liver, eye, maxillofacial region and brain)
Eggs from ----auto-infection, external
Eggs from ----auto-infection, internal
Eggs from ----external

21. auto-infection internal
Egg
man
man
external
Egg
auto-infection
external

22. Pathogenesis and clinical features
Adult worm —Teaniasis
Light infections remain asymptomatic
Heavier infections may produce abdominal discomfort, epigastric pain, vomiting and diarrhea

23. Metacestode stage –Cysticercosis
The cysticercus stage of T. solium can be found anywhere in the body -- subcutaneous, muscles, eye, brain
Regardless of the tissue affected, pathological consequences are those of a space-occupying lesion
Cysticerci in brain tend to grow a larger size than those in other tissues
The process of calcification may be accompanied by the release of antigens -- inflammatory reaction

24. Cysticercosis
The incidence of cerebral cysticercosis can be as high 1 per 1000 population and may account for up to 20% of neurological case in some countries (e.g., Mexico); cysticercosis ocular involvement occurs in about 2.5% of patients and muscular involvement is as high as 10% (India).

25. Cysticercus on the eyeground
subcutaneous nodules
pseudohypertrophy of muscle

26. Cysticerci in brain

27. Cysticerci in heart

28. Cysticerci in tongue

29. DIAGNOSIS For adult worm infection (Teaniasis)
＊ History of eating raw pork
＊ Find gravid proglottids in feces
＊ Perianal swab to find eggs

30. For cysticercosis
＊ Specific diagnosis is difficult to establish, the history and adult worm infection attribute to strong suspicion
＊ Biopsy to subcutaneous lesions
＊ Computerized axial tomography or magnetic resonance imaging
＊ Serological examination for specific antibody

32. Epidemiological distribution
World-wide distribution.
Epidemic in central and south America (Mexico), Africa,
South-east Asia, eastern Europe, Micronesia .
High prevenlence
Medium prevelence
Low or no prevelence
Epidemic limited area
Data unavialable

33. PRINCIPLES OF CONTROL
Treat all patients to eradicate the source of larvae parasitism
Pumpkin seed and areca nut ;
Praziquantel
Avoid the fecal contamination of pig feed
Modernization of raising pigs
Pay attention to personal and food hygiene
Intensive examination of the pork
Adequate cooking or freezing of meat are effective precautions
cysticerci do not survive at temperatures below -10℃ and above 50 ℃.

34. Customs of pig husbandry

35. Teania saginata Can be up to 4 to 8 meters long
The scolex with four suckers
The gravid proglottids with a branched uterus
The eggs of T. solium and T. saginata are indistinguishable

37. gravid proglottid of T. solium
gravid proglottid of T. saginata

38. LIFE CYCLE

39. LIFE CYCLE
Human is the only definitive host, cattle is the intermediate host
Adult worm reside in the lumen of the upper part small intestine
The infective stage to man is larva
No cysticercus in human

40. PATHOGENESIS The adult parasite induces some host reaction
The process of calcification may be accompanied by the release of antigens -- inflammatory reaction

41. DIAGNOSIS For adult worm infection
Find gravid proglottids in feces or experimental inducing worm

42. DISTRIBUTION
T.saginata is prevalent in regions where cattle are raised: Africa, Middle-East, Central and South America, Europe and Asia.

43. PRINCIPLES OF CONTROL
Treat the patients --Pumpkin seed and areca nut; Praziquantel
Modernization of raising cattle
Intensive examination of the beef

44. COMPARISON OF THE TWO TAPEWORMS
T. solium
T. saginata
Size
Scolex
Mature Proglottid
Gravid proglottid
Intermediate Host
Disease caused
Infective stage
Mode of infection
Diagnosis
Clinical significance
Chemotherapy
2-4m
Rostellum & hooks
3 lobes of ovary
Uterine Branches<13
Swine & Human
Taeniasis & cysticercosis
Egg & Cysticercus
Cross or autoinfection
Egg may be found in stool
Much more important
Should be instant
4-8m No
2 lobes of ovary
>15
Cattle
Taeniasis only
Cysticercus Only
Cross only
Perianal egg exam
Less than T. solium
Not so urgent