Class Cestoda: The Class Cestoda: The tapeworms tapeworms • Exclusively endoparasites Exclusively endoparasites • Body covered by a tegument Body covered by a tegument • Body consists of an anterior Body consists of an anterior scolex, followed by a short scolex, followed by a short neck and then a strobila neck and then a strobila composed of a series of composed of a series of “segments” or proglottids. “segments” or proglottids. • Digestive track absent. Digestive track absent.
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Class Cestoda: The tapeworms Exclusively endoparasitesExclusively endoparasites Body covered by a tegumentBody covered by a tegument Body consists of an.
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Class Cestoda: The tapewormsClass Cestoda: The tapeworms
• Body covered by a tegumentBody covered by a tegument
• Body consists of an anterior scolex, followed Body consists of an anterior scolex, followed by a short neck and then a strobila by a short neck and then a strobila composed of a series of “segments” or composed of a series of “segments” or proglottids.proglottids.
• Digestive track absent.Digestive track absent.
Scolex, anterior holdfast organ
Neck, region of growth
Strobila made up of individual proglottids.
Three types of proglottids: immature, mature and gravid.
SEM of a Scolex
Diversity of scolexes.
Adult TapewormsAdult Tapeworms
You will be responsible for 2 orders of You will be responsible for 2 orders of tapeworms!tapeworms!
• Phylum PlatyhelminthesPhylum Platyhelminthes
– Class: CestoideaClass: Cestoidea
• Subclass EucestodaSubclass Eucestoda
–Order PseudophyllideaOrder Pseudophyllidea
–Order CyclophyllideaOrder Cyclophyllidea
Life CyclesLife Cycles
• Adult tapeworms live in the intestine of Adult tapeworms live in the intestine of vertebrates specifically the small intestine.vertebrates specifically the small intestine.
• Eggs pass in the feces of vertebrate host.Eggs pass in the feces of vertebrate host.
• Larval stage in egg = onchosphere.Larval stage in egg = onchosphere.
• It is spherical and has 6 hooks (hexacanth).It is spherical and has 6 hooks (hexacanth).
Generalized Pseudophyllidean Life CycleGeneralized Pseudophyllidean Life CycleAquatic Life CycleAquatic Life Cycle
Adult in Vertebrate Small IntestineAdult in Vertebrate Small Intestine
Uterine pore
Eggs released; later chains of spent proglottids
Eggs are usually operculated and Eggs are usually operculated and unembryonated when laid. unembryonated when laid.
The oncosphere develops in the egg and The oncosphere develops in the egg and a free swimming larva the Coracidium a free swimming larva the Coracidium
hatches.hatches.
The first larval stage the The first larval stage the CoracidiumCoracidium
CoracidiumCoracidium
The free swimming coracidium is eaten The free swimming coracidium is eaten by 1by 1stst intermediate host usually an intermediate host usually an
aquatic arthropod!aquatic arthropod!
CopepodCopepod
In the copepod the second larval stage In the copepod the second larval stage (PROCERCOID)(PROCERCOID)
Frontal glands
Cercomer posterior end
22ndnd IH is a vertebrate of some kind IH is a vertebrate of some kind (usually cold blooded)(usually cold blooded)
The 3The 3rdrd type of larva that develops in the type of larva that develops in the 22ndnd IH is the PLEROCERCOID IH is the PLEROCERCOID
The cercomere is lost and a scolex develops (no proglottids)!
Life cycle of Ligula intestinalis
Generalized Cyclophyllidean Life CycleGeneralized Cyclophyllidean Life CycleTerrestrial Life CycleTerrestrial Life Cycle
Adults live in the small intestine of Adults live in the small intestine of vertebrates.vertebrates.
Eggs passed not by uterine pore but Eggs passed not by uterine pore but instead by short chains or terminal instead by short chains or terminal proglottids that split open to release proglottids that split open to release
eggs!eggs!
Only one IH can be vertebrate or Only one IH can be vertebrate or invertebrate depending on species of invertebrate depending on species of
tapeworm!tapeworm!
• The type of larval stage that develops varies The type of larval stage that develops varies depending on species of tapeworm!depending on species of tapeworm!
• Anterior vesicle with Anterior vesicle with scolex invaginated; scolex invaginated; solid posterior with solid posterior with tail-like region; in tail-like region; in arthropods!arthropods!
CysticercusCysticercus
• Central cavity; fluid-Central cavity; fluid-filled; invaginated filled; invaginated scolex; in reptiles or scolex; in reptiles or mammals, rarely mammals, rarely birds!birds!
CysticercusCysticercus
StrobilocercusStrobilocercus
• Strobiloceroid-a Strobiloceroid-a simple cysticercus simple cysticercus in which some in which some strobilation occurs strobilation occurs in the cyst.in the cyst.
CoenurusCoenurus
• Bladder with multiple Bladder with multiple scolices; in mammals; scolices; in mammals; hydatid cyst a special hydatid cyst a special case!case!
Hydatid CystsHydatid Cysts
Secondary brood cysts
Hydatid CystsHydatid Cysts
Alveolar hydatid cyst in a mouse - cyst metastasizes from the liver to fill the body cavity
Alveolar Hydatid CystsAlveolar Hydatid Cysts
PseudophyllideaPseudophyllidea
Diphyllobothrium latumDiphyllobothrium latum
• Broad fish tapewormBroad fish tapeworm
• Fish eating mammalsFish eating mammals
• Scandinavia, Baltic States, Russia, Great Scandinavia, Baltic States, Russia, Great Lakes, West coast of N. AmericaLakes, West coast of N. America– unusualunusual
• 9 million people infected9 million people infected
• 10 meters long10 meters long
• 1 million eggs per day1 million eggs per day
Life cycle of Diphyllobothrium
latum
The broad fish tapeworm
Coracidium
Procercoid
Plerocercoid
Pike and salmon common hosts Paratenic host
Pathology and SymptomsPathology and Symptoms
• Attaches to small intestineAttaches to small intestine
• Pathogenicity variesPathogenicity varies– AsymtomaticAsymtomatic– Abdominal discomfort, diarrhea, nauseaAbdominal discomfort, diarrhea, nausea– Megaloblastic Anemia (caused by loss of Megaloblastic Anemia (caused by loss of