Metacestodes / Bladder worm

Metacestodes are infective larval stage of cestodes that parasitize the I/H.
An embryonated egg containing Onchosphere / coracidium enters in the I/H and then passes through developmental stages and don’t reach to sexual maturity, called Metacestodes / Bladder worm.

i)Cysticercos:Fluid-filledcystcontaininganattachedsingle
invaginatedscolex,sometimcscalledaprotoscolex.e.g;T.saginata
ii)Coenurus:
Similartoacysticercus,butwithnumerous
invaginaledscolices.e.g;Multicepsmulticeps
iii)Strobilocercus:
Thescolexisevaginatedandisconnectedtothecyst
byachainofasexualproglottids.Thelatteraredigested
awayalteringestionbythefinalhost,leavingonlythescolexe.g,T.taeniaeformis..
iv)Hydatid:Thisisalargefluid-,surroundedbygerminal
epithelium(hroodcapsules).Thecontentsofthecysts
otherthanthefluid,i.e.scolicesandbroodcapsules.
arefrcqucntlydescribedas’hydatidsand’.Occasiunally
also,daughtercystscompletewithcuticlcandgerminal
layerareformedendogenouslyor,ifthecyst
wallruptures,exogenously.e.g;Echinococcussp.
v)Cysticercoid:
Asinglecvaginatedscolexembeddedinasmallsolid
cyst.Typicallyfoundinverysmallintermcdiatchosts
suchasarthropods.E.g;D.caninum.
vi)Tetrathyridium:
Worn-likelarvawithaninvaginatedscolex:found
onlyinMcaocestoididae.
Whenthemetacestodeisingestedhythefinalhostthe
scolexattachestothemucosa,thercmainderofthe
structureisdigestedoff,andachainofproglottids
beginstogrowfromthebaseofthescolex.
Thcscvcnmainfamiliesofveterinaryinterestin
theorderCyclophyllideaaretheTaeniidae,Anoplocephulidae,
Dilrpididuv,Davaineidae,Hymenolepididue.
MesocvstoididurandThysanosomidae.
onlythescolex.’Theadultsarefoundindomcsticcarnivoresandman.e.g;Metacestoidess
7 .Pracercoid:
• It is solid bodied; bear hooks in the posterior region.
• It is the first metacestode stage in the I/H of pseudophyllidea. Eg. Didhylobothrium sp.
8. Plerocercoid:
• It is the solid bodied bear scolex.
It is the 2nd metacestode in 2nd I/H of the pseudophyllidea. Eg. Didhylobothrium sp.
• Where; 1-6 In Cyclophyllidea. 1-5 Cystic
7-8In pseudophyllidea
6-8Acystic