Cestodes Flashcards
What are cestodes?
- Tapeworms
- Segmented
- Bilat. sym.
- 2/4 suckers
- No intestinal canal
- Their larvae develop in intervertebrates/vertebrates
- Hermaphrodites
- Scolex: anterier part that attaches to wall of intestine
- Rostellum: protrustion on scolex, with suckers and sometimes hooks
- Unsegmented neck
- Strobila: segmented part buildt by proglottidis
- Each proglottid has sexual organs inside
- Mature segment: many testicles, biolobed ovary, genital ducts and a copulatory organ
- Autocopulation (self mating) - sexual organs replaced by eggs (gravid phase of proglottid)
Most important cestodes
- Ruminants: Moniezia expansa and M.benedeni
- Equines: Anoplocephala perfoliata and A. magna
- Flea/cucumber: Diphylidium caninum
- Broad/fish: Diphyllobothrium latum
- Taenia of Ca: T. pisiformis, T.hydatigena, T.ovis, T.cervi, T.crassiceps, T.taeniformis
- Taenia of Hu: T.solium and T.saginata
- Taenia of canines: T.multiceps and T.serialis
- Echinococcus: E.granulosus and E.multilocularis
Difference between the mature segments
•Cucumber tapeworm:
o 2 sets of genitalia, GO on both sides
o Longer than broad
•Fish tapeworm:
o More broad than long
o Can see the sexual organs clearly
o One set of genitalia: central female parts (bilobed ovary), testicles scattered around
o GO in the middle
•Moniezia:
o 2 sets of genitalia, GO on both sides
o Row of interproglottidal glands
•Anoplocephala:
o Only 1 set of genitals, GO on only one side
o No interproglottidal glands
•Taenia worms:
o More long than broad (immature segments more broad than long)
o Only 1 set of genitals
o One GO on only one side – irregular alternating position
o Species can be distinguished from each other by the shape of uterine branches of segments
o E.granulosus: 3 segments, E.multilocularis: 5 segments
o If only one excretory tube = Taenia
Difference between head parts
•Cucumber tapeworms: armed scolex with 4 acetabuli/suckers and hooked rostellum
•Fish tapeworm: unarmed, club-shaped scolex with two elongated bothrida
•Moniezia: unarmed scolex with 4 suckers/acetabuli – same as Anoplocephala! (head is smallest part)
•Anoplocephala: unarmed scolex with 4 suckers
•Taenia: armed scolex with 4 suckers and a hooked rostellum – hooks big and strong
o T.saginata: no hooks
Difference between the eggs
-Cucumber tapeworm: large (500 um) cocoons with several eggs, 6 hooked oncosphera
-Fish tapeworm: similar to rumen fluke eggs but smaller, colourless, NO oncosphera inside, only zygote and yolk cells (everyone else has 6 hooked oncosphera)
-Moniezia expansa: Triangular, 6 hooked oncosphera is central
-Moniezia benedeni: quadrangular, 6 hooked oncosphera is eccentric
-Anoplocephala: semi-circular, 6 hooked oncosphera, “horse shoe”
-Taenia type eggs:
o Small - 30-40 um, thick-shelled
o 6-hooked oncosphera inside
o Cannot distinguish spp. based on eggs
o Echinococcus similar eggs
o If brownish → bile discoloration
Differences between the larvaes
•Cucumber, Anoplocephala and Moniezia: Cysticercoid - 100 um, spherical shaped, one scolex in an outer envelope (similar to adult), no space bw. the scolex and it´s wall
•Fish tapeworms:
o Coracidium in water (ciliated oncosphere)
o Procercoid in crustaceans
o Plerocercoid in freshwater fish
o Tiny cylindrical larva in the arthropod, but large, elongated worm in the fish
o Plerocercoid resembles to the adult showing pseudo-segmentation and having a scolex
•Taenia:
o Cysticercus pisiformis, tenuicollis, ovis, cervis, longicollis and fasciolaris: 1-5 cm, spherical or oval, one scolex surrounded by a capsule (similar to adult), wide space bw. the scolex and it´s wall
o Cysticercus cellulosae (T.solium) and bovis (T.saginata): 1-2 cm (pea), spherical or oval, same scolex as above
o Coenurus cerebralis (T.multiceps) and serialis (T.serialis): spherical/plat, contains hundreds of scolices surrounded by a capsule (similar to adult), space contains lots of liquid material and scolices attach to the wall.
• Echinococcus hydatidosus: hydatid cyst of E.granulosus – cyst separated or rarely connected with a non-divided cavity (up to 20 cm), filled with fluid containg protoscolices floating freely. Exo-/endogenous daughter cysts can develop from inner germinal layer of cyst wall
• Echinococcus alveolaris: alveolar system of E.multilocularis – connected net of caverns with a divided cavity filled with membranes and gelatinous mass containg free protoscolices.
- Both Echinococcus larvae have 3-layered wall: outer CT – cell-free laminar layer – inner germinal epithelium.
How to detect
•Flotation:
o Flea/cucumber: large egg capsules
o Fish tapeworms: Egg similar to Fasciola egg, but smaller and frequently contains blastomeres inside
o Moniezia: angular eggs (triangular/quadrangular)
o Anoplocephala: semi-circular eggs
o Taenia: small, “taenia-type” (30-40um), thicked shelled, brown eggs
•Gravid segments in feces:
o Flea/cucumber: usually, pinkish, 2-3mm long and able to crawl for a short distance
o Moniezia: whole segments can be shed by heavily infected lambs on surface of fecal balls
o Taenia: rarely – whitish, 4-10mm long
•Empty segments in feces: fish tapeworms (maybe)
•Moniezia + Anoplocephala: collection of mites from soil with funnel
•Flea/cucumber: collection of fleas/lice from infected host/dog houses
•Anoplocephala: Whole segments can be shed by heavily infected lambs on the surface of fecal balls
Intermediate host
- Fish/broad: 1st tiny freshwater crustaceans and 2nd freshwater fish
- Flea/cucumber: Ctenocephalides fleas and rarely hair lice (Trichodectes canis)
- Moniezia and Anoplocephala: box mite
- Taenia pisiformis, hydatigena, ovis, cervi, crassiceps and taeniaeformis, also T.multiceps, T.serialis and Echinococcus: prey mammals of the final host, Echinococcus also humans
- Taenia solium and saginata: swine and cattle, sometimes humans for T.solium
Definitive host
- Fish/broad: fish-eating mammals, including humans
- Flea/cucumber: canines, rarely cats and humans
- Moniezia: ruminants – domestic and wild
- Anoplocephala: equines – domestic and wild
- Taenia pisiformis, hydatigena, ovis, cervi, crassiceps: all canines except cats
- T.taeniaeformis: cats
- T.multiceps and T.serialis: canines except cats (dogs, foxes, wolfes)
- Echinococcus granulosus and multilocularis: canines (dogs, foxes, wolfes), rarely cats
- Taenia solium and saginata: humans
Predilection sites
•Flea/cucumber: body cavity of arthropod (fleas and lice)
•Fish/broad: body cavity of host (tiny freshwater crustaceans and freshwater fish)
•Moniezia: body cavity of arthropod (box mite)
•Anoplocephala: body cavity of arthropod (box mite)
•Carnivorous Taenia (pea size)
o T.pisiformis – c.pisiformis: liver+mesentery (rabbit+hares)
o T.hydatigena - c.tenuicollis: liver+mesentery (walnut size, ungulates)
o T.ovis - c.ovis: skeletal muscle (sheep)
o T.cervi - c.cervi: skeletal muscle (goat)
o T.crassiceps – c.longicollis: body cavity (rodent)
o T.taeniaeformis – strobilocercus fasciola: liver (rodents)
•T.solium: cysticercus cellulosae - skeletal muscles (pig), brain or eyes of Hu
•T.saginata: cysticercus bovis - skeletal muscles of cattle (mainly masseter, eso., tongue, diaph., heart)
•T.multiceps – coenurus cerebralis: CNS (mainly brain) (small Ru, exceptionally cattle, pig, horse, Hu)
•T.serialis – coenurus serialis: CT subcutaneous or intramuscular (hares)
•Echinococcus granulosus: liver (rodents + Hu)
•Echinococcus multilocularis: parenchymal organs and BM (mainly liver in Bo, Su, Eq, Hu and lungs in sheep and goat)
