Must Know in Cestodes (Tapeworms): Clinical Parasitology
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Course
Clinical Parasitology
Institution
Centro Escolar University
Book
Clinical Parasitology
The document contains:
- Developmental stage of cestodes
- Groups of tapeworms in table form
- Parts of cestodes in table form
- Pseudophyllidea vs Cyclophyllidea
- Cestodes and its mature segments
- Distinguishing features, size, and ova of cestode species
- Pathology of cestode species
- ...
CESTODES
Phylum Platyhelminthes
Class Cestoda: Tapeworms
General characteristics:
▪ Exclusively HERMAPHRODITIC (Adult stage / worm) (but eggs are still produced)
▪ NO digestive/circulatory systems, adult worms w/ flat, _______, Ribbon-like bodies
▪ Average life span is 20 years
▪ Adult tapeworms inhabit the intestinal tract (small intestine); LARVA inhabits tissues.
Adult worm in SI (Definitive host) Larval stage in man (accidental Intermediate Host)
Diphyllobothrium latum Spirometra mansoni
Taenia solium Diphyllobothrium latum
Taenia saginata Taenia solium
Hymenolepis nana Echinococcus granulosus
Hymenolepis diminuta Multiceps multiceps
▪ All tapeworms cause intestinal infection except E. granulosus
▪ E. granulosus are warm blooded animals
▪ 3 DEVELOPMENTAL STAGES: EGG → LARVA → ADULT
▪ All are HETEROXENOUS except for Hymenolepis nana (HOMOXENOUS but can also be
heteroxenous sometimes)
* H. nana has 2 life cycles:
o 1 direct: 1 host (H. nana is homoxenous) → COMMON
o 1 indirect cycle: 2 host (H. nana is heteroxenous) → NOT COMMON
▪ Body is flattened ribbon-like segmented, covered by a resistant cuticle
▪ MOT: Ingestion
▪ Cestodes to complete their cycle they need 2 hosts: 1 intermediate and 1 definitive
host. D. latum however requires 3 hosts: 1 definitive and 2 intermediate hosts (1st and
2nd intermediate hosts)
- Man is usually the definitive host (adult), however, in E granulosus, man is an
accidental IH (larva)
- So all can be detected through stool exam except in E. granulosus bcos this is a
tissue infection, so it is detected thru serologic test.
▪ In treating cestodes, a treatment that fails to recover the scolex and neck is a fail. Dapat
buo, hindi pwedeng kulang ha? Bawal segment segment lang, kapag kulang, reject yan.
Hindi tayo tumatanggap ng kulang dito.
▪ In stool exam/fecalysis, we do not look for SEGMENTS, instead, we look for EGGS, but it
is possible to see segments in stool exam.
▪ 3 MOST IMPORTANT CESTODES:
* D. latum
* T. solium
* T. saginata
, 2 GROUPS OF TAPEWORMS
PSEUDOPHYLLIDEA species COMMON NAME CYCLOPHYLLIDEA species COMMON NAME
False tapeworms True tapeworms
Taenia solium Pork tapeworm
Ex. Fish Broad Armed tapeworm
Diphyllobothrium latum Tapeworm / Russian Taenia saginata Beef tapeworm
Broad tapeworm Unarmed tapeworm
Hymenolepis nana Dwarf tapeworm
Hymenoepis diminuta Rat tapeworm
Dipylidium caninum Dog tapeworm
Double Pored tapeworm
Echinococcus granulosus Hydatid worm
PSEUDOPHYLLIDEA species CYCLOPHYLLIDEA species
1. SCOLEX
2. SEGMENTS
a. Genital pore CENTRAL LATERAL
b. Uterine pore CENTRAL ABSENT
c. Apolysis ABSENT PRESENT
3. OVA UNEMBRYONATED, OVOID EMBRYONATED, SPHERICAL
4. INTERMEDIATE HOST
Parts of the tapeworm body
1. SCOLEX / HEAD: hold fast organ, organ for attachment, may be equipped w/ ROSTELLUM & hooks
o Organ adapted for attachment (to SI) may be equipped with rostellum and hooklets
o All tapeworms have scolex / head
o Has 2 types:
▪ GLOBULAR: Have 4 true suckers. (all under Cyclophyllidea);
* Globular (w/out hooks): Hymenolepis diminuta and Taenia saginata
* Globular (w/ hooks): Hymenolepis nana, Taenia solium, Dipylidium
caninum & Echinococcus granulosus
A. ROSTELLUM: Prolongation of scolex (extension); attached here are hooks
Ex. Taenia solium
B. HOOKLETS
▪ SPATULATE / ALMOND / SPOON-SHAPED: equipped with 2 false suckers (sectorial
grooves) called bothria aka suctorial grooves.
* Ex. is only Diphyllobothrium latum (non-globular scolex/head)
2. NECK: Budding zone, consist of germinative tissues; Region of growth for strobila where
segments originate
3. SEGMENTS / PROGLOTTIDS: Called Strobila/trunk if it is a chain or an entire chain of segments
a. Immature: Next to the neck; Sexually undeveloped
b. Mature: Sexually developed (has a complete set of male & female reproductive
organs); Hermaphroditic
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