Difference between revisions of "Cyclophyllidea Life-Cycle"

Latest revision as of 17:37, 4 January 2023

Dipylidium caninum - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine

Overview

Cyclophyllidea cestodes have an indirect life cycle involving one or more intermediate hosts before developing into adult form in the definitive host. Eggs must be ingested by an intermediate host species, once ingested the gastric and intestinal secretions breakdown the thick shell and activate the 6-hooked oncosphere. The oncosphere uses its hooks to tear through the gastrointestinal mucosa to reach the blood or lymph system. In invertebrate hosts the oncosphere will enter directly into the body cavity from the gastrointestinal tract. The oncosphere then travels to its predeliction site, loses its hooks and develops into the larval stage known as a metacestode. This can be one of a number of forms dependent on the species of cestode. When the metacestode is ingested by the final host, the scolex attaches to the gastrointestinal mucosa, the remainder of the structure is digested, and a chain of proglottids (segments) begins to grow from the base of the scolex. Eggs are produced within the terminal proglottid of the chain which is shed into the feaces of the host once the production is complete.
Infection of the final-host involves at least three epidemiological relationships:
1) predator-prey, e.g. cat eating infected mouse
2) accidental, e.g. horse eating infected pasture mites
3) irritation, e.g. infected flea on animal → exaggerated grooming of animal → swallowed

Metacestodes

There are six types of metacestode (in increasing order of complexity:

Cysticercus

This is a simple metacestode consisting of a fluid filled bladder containing a single inverted scolex.

Cysticercoid

This is a simple metacestode that is only found in invertebrates. It is small, pinhead sized, and instead of a bladder has a potential space containing a single scolex that is not inverted.

Strobilocercus

This metacestode is only formed by the cat tapeform Taenia taeniaeformis and is similar to a cysticercus however the single scolex is attached to the containing bladder by a chain of segments.

Coenurus

Similar in form to the cysticercus, however the coenurus contains multiple inverted scolices.

Hydatid cyst

This metacestode consists of a fluid filled bladder that can grow to a considerable size. It is lined by a germinal epithelium that buds off to form brood capsules. These brood capsules contain multiple inverted scolices and are termed hydatid sand. The response from the host is to wall off the cyst with fibrous tissue around the germinal layer.

Alveolar cyst

Similar to the hydatid cyst however the alveolar cyst forms daughter cysts, these bud off from the internal and external surface of the germinal layer. These buds enable the cyst to invade into the tissue of the organ rather like a tumor.

Cyclophyllidea Life-Cycle Learning Resources
Vetstream To reach the Vetstream content, please select	Canis, Felis, Lapis or Equis
Flashcards Test your knowledge using flashcard type questions	Cestode Flashcards
Literature Search Search for recent publications via CAB Abstract (CABI log in required)	Cestode life cycle publications

Webinars

Failed to load RSS feed from https://www.thewebinarvet.com/infection-control-and-biosecurity/webinars/feed: Error parsing XML for RSS

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 [[Image:Dipylidium caninum 2.jpg|right|150px|thumb|''Dipylidium caninum'' - Courtesy of the Laboratory of Parasitology, University of Pennsylvania School of Veterinary Medicine]]
-Indirect with one or more intermediate hosts. When the egg is ingested by the intermediate host, the gastric and intestinal secretions digest the thick shell and activate the 6-hooked oncosphere. Using its hooks, it tears through the mucosa of the host to reach the blood or lymph system, or in the case of invertebrates, the body cavity. Once it has reached its predilection site, the oncosphere loses its hooks and develops, depending on the species, into one of the following larval stages, known as a metacestode. There are six types of metacestode (in increasing order of complexity:
+==Overview==
+[[Cyclophyllidea]] cestodes have an indirect life cycle involving one or more intermediate hosts before developing into adult form in the definitive host. Eggs must be ingested by an intermediate host species, once ingested the gastric and intestinal secretions breakdown the thick shell and activate the 6-hooked oncosphere. The oncosphere uses its hooks to tear through the gastrointestinal mucosa to reach the blood or lymph system. In invertebrate hosts the oncosphere will enter directly into the body cavity from the gastrointestinal tract. The oncosphere then travels to its predeliction site, loses its hooks and develops into the larval stage known as a metacestode. This can be one of a number of forms dependent on the species of cestode. When the metacestode is ingested by the final host, the scolex attaches to the gastrointestinal mucosa, the remainder of the structure is digested, and a chain of proglottids (segments) begins to grow from the base of the scolex. Eggs are produced within the terminal proglottid of the chain which is shed into the feaces of the host once the production is complete.
+<br/>
+Infection of the final-host involves at least three epidemiological relationships:<br/>
+)	'''predator-prey''', e.g. cat eating infected mouse<br/>
+)	'''accidental''', e.g. horse eating infected pasture mites<br/>
+)	'''irritation''', e.g. infected flea on animal → exaggerated grooming of animal → swallowed
+==Metacestodes==
+There are six types of metacestode (in increasing order of complexity:
+===Cysticercus===
+This is a simple metacestode consisting of a fluid filled bladder containing a single inverted scolex.
+===Cysticercoid===
+This is a simple metacestode that is only found in invertebrates. It is small, pinhead sized, and instead of a bladder has a potential space containing a single scolex that is not inverted.
-)	'''Cysticercus''': a fluid-filled bladder with one inverted scolex
+===Strobilocercus===
+This metacestode is only formed by the cat tapeform ''[[Taenia taeniaeformis]]'' and is similar to a cysticercus however the single scolex is attached to the containing bladder by a chain of segments.
-)	'''Cysticercoid''': pinhead size; only found in invertebrates; like the cysticercus, but the bladder is reduced to a potential space and the scolex is not inverted
+===Coenurus===
+Similar in form to the cysticercus, however the coenurus contains multiple inverted scolices.
-)	'''Strobilocercus''': restricted to the cat tapeworm Taenia taeniaeformis; like a cysticercus, but the single scolex is attached to the bladder by a chain of segments
+===Hydatid cyst===
+This metacestode consists of a fluid filled bladder that can grow to a considerable size. It is lined by a germinal epithelium that buds off to form brood capsules. These brood capsules contain multiple inverted scolices and are termed '''hydatid sand'''. The response from the host is to wall off the cyst with fibrous tissue around the germinal layer.
-)	'''Coenurus''': like a cysticercus, but has multiple inverted scolices
+===Alveolar cyst===
+Similar to the hydatid cyst however the alveolar cyst forms daughter cysts, these bud off from the internal and external surface of the germinal layer. These buds enable the cyst to invade into the tissue of the organ rather like a tumor.
-)	'''Hydatid cyst''': the metacestode of Echinococcus granulosus; this fluid-filled bladder can grow to the size of a football; it is lined with germinal epithelium that buds off brood capsules internally; inverted scolices form inside these; hydatid sand is the name given to the brood capsules and scolices in the hydatid fluid; the host attempts to wall off the hydatid cyst with fibrous tissue; between this and the germinal membrane is an amorphous layer
+{{Learning
+|flashcards = [[Cestodes_Flascards|Cestode Flashcards]]
+|literature search = [http://www.cabdirect.org/search.html?q=%28%28title%3A%28cestode%29+AND+title%3A%28%22Life+Cycle%22%29%29%29+OR+%28%28title%3A%28Cyclophyllidea+%29+AND+title%3A%28%22Life+Cycle%22%29%29%29 Cestode life cycle publications]
+|Vetstream = [https://www.vetstream.com/canis/search?s=tapeworm Cestoda]
+}}
-)	'''Alveolar cyst''': the metacestode of Echinococcus multilocularis; this is like the hydatid cyst, but daughter cysts bud off the external, as well as the internal, surface of the germinal layer, with the result that the metacestode expands by infiltrating through the tissue, rather like a tumour.
-When the metacestode is ingested by the final host, the scolex attaches to the mucosa, the remainder of the structure is digested, and a chain of proglottids (segments) begins to grow from the base of the scolex.
+{{review}}
-Infection of the final-host involves at least three epidemiological relationships:
+==Webinars==
+<rss max="10" highlight="none">https://www.thewebinarvet.com/infection-control-and-biosecurity/webinars/feed</rss>
-)	'''predator-prey''', e.g. cat eating infected mouse
+[[Category:Cyclophyllidea]]
-)	'''accidental''', e.g. horse eating infected pasture mites
-)	'''irritation''', e.g. infected flea on animal = exaggerated grooming of animal = swallowed[[Category:Cyclophyllidea]]
+[[Category:Expert_Review]]