Cestodes Mbbs

CESTODES

CESTODES  Tape worms  Flat and ribbon like, segmented  Head or scolex of the worm has 4

muscular cup-shaped suckers for attachment, hooklets  Individual Segments are proglottids and chain of proglottids are strobila

 Hermaphroditic  Eggs are non operculated

and has 6 hooked embryo- hexacanth embryo (exception-Diphyllobothrium latum)

TYPES  Taenia solium  Taenia saginata  Diphyllobothrium latum  Echinococcus granulosus  Echinococcus multilocularis  Hymenolepis nana  Hymenolepis diminuta  Dipylidium caninum

TAENIA SOLIUM  Pork(pig) tape worm/cysticercosis  Reservoir for larvae-hogs, humans  Reservoir for adults-humans

Life cycle of taenia

 Infective stage - cysticerci (bladder worm) in the

muscle of pigs  Reaches the small intestine of humans,attaches.  Worm produces proglottids,which when mature contain eggs  And leave the host in feces->pigs  In pigs intestine->6 hooked larval form>oncosphere->cysticerci

Clinical features  Adults  Abdominal discomfort,c/c indigestion,diarrhoea  Cysticercus (larval stage)  Cysticerci in the brain causes-meningitis,

hydrocephalus, cranial nerve damage, seizures  In the eye-visual field defects

Lab diagnosis  



Stool examination-eggs and proglottids Eggs-spherical,possess a thick radially striated shell containing a 6 hooked embryo Proglottids of T.solium are smaller than saginata and contain only 7-13 uterine branches versus 15-30 for beef tapeworm

 Presence of cysticerci-soft tissue

xrays,visualisation in the eye  CT,radio isotope scanning or ultrasonography detects CNS lesions

Treatment and prevention  DOC-niclosamide  Avoid consumption of undercooked pork  In cysticercosis- DOC-praziquantel or

albendazole  Surgical removal of the cysts may be required

TAENIA SAGINATA  Beef tapeworm  Reservoir-cattle,humans  Does not produce human cysticercosis  Clinical features similar to intestinal

infection with T.solium.ie,generally asymptomatic,but has vague abdominal pains,c/c indigestion

 Diagnosis – eggs and proglottids;the

adult worm has scolex which lacks the hooklets  DOC-niclosamide  Properly cooked beef

DIPHYLLOBOTHRIUM LATUM  Fish tapeworm  One of the largest tapeworms  Reservoir for larvae-fresh water

crustaceans and fish  Reservoir for adultshumans,dogs,cats,bears

 Scolex-has long lateral grooves(bothria)-

for attachment  Proglottids-broad,has a central uterine structure,produces eggs with an operculum (ROSE APPEARANCE)  Larval form- sparganum /plerocercoid larva(in the flesh of fresh water fish)

Ciliated Free swimming larval formcoracidium  Disease occurs on consumption of inadequately cooked fish  Seen in regions where raw or pickled fish is common 

Life cycle

Clinical features  Most are asymptomatic  Occasionally,epigastric pain,abdominal

cramps,nausea,vomiting and weight loss  There is vit B 12 deficiency associated with it-megaloblastic anemia and neurologic manifestations

Diagnosis  Stool examination-

Eggbile stained, operculated egg with its knob at the bottom of the cell. o proglottids-typical rosette uterine structure o

Treatment  DOC- niclosamide  Vit.B12 supplementation  Avoid undercooked fish  Proper disposal of feces

ECHINOCOCCUS GRANULOSUS  Or unilocular hydatid cyst disease  Reservoir for larvae- herbivores (sheep)

and humans  Reservoir for adults- canines

Life cycle

 Adult tape worms only in canine intestine-

>infective eggs  Eggs ingested by humans->hatch to form a 6 hooked larvae-ONCOSPHERE  It penetrates intestine and enters circulation to reach various tissues mainly, liver and lungs forms HYDATID CYST

 This cycle occurs in the

herbivores which when killed by canines, ingest the cysts and produce adult tape worms, excretes the egg to continue the cycle

 HYDATID CYST-slow growing,tumor like

space occupying structure,enclosed by a germinative membrane.it produces brood capsules on the wall – tape worm head (protoscolices) develop here

 Daughter cysts also develop in the original

mother cyst  Accumulate fluid,which Is toxic  If spilled into body cavity-anaphylactic shock and death

 Finally the daughter cysts and brood

capsules disintegrate,liberating the protoscolices—HYDATID SAND  This type of echinococcus cyst is called unilocular cyst.

Clinical features  Pressure effects of the slowly growing cyst

is the 1st symptom  In liver-pressure on bile ducts and blood vessels and create pain and biliary rupture  Lungs-cough,dyspnoea and chest pain  Also disseminated infection affecting the bone and brain

Diagnosis  difficult;mainly based on

clinical,radiological,serological findings  Surgical removal is the treatment of choice  If inoperable,-high dose albendazole,mebendazole,praziquantel  Proper hygeine

HYMENOLEPIS NANA  Dwarf tape worm  No intermediate host,but beetles and mice

may be infected  In heavy infections,diarrhoea,abdominal pain,headache

Life cycle

Diagnosisdemonstration of egg in stool sample  Egg of hymenolepis nanaThin shelled with a 6 hooked embryo

Treatment ,prevention  DOC- praziquantel  Improved sanitation

DIPYLIDIUM CANINUM  

 

Primarily a parasite of dogs and cats In children whose mouths are licked by pets Also called pumpkin seed tapeworm Eggs-colorless ,occur in packets covered by a tough clear membrane

 Heavier worm load-abdominal

discomfort,anal pruritis,diarrhoea  Stool examination- characterstic eggs  DOC- niclosamide  Deworming of dogs and cats