Cestodes Flashcards
Cestodes “tapeworms”
Structure
- Segmented body
- No alimentary tract
- hermaphroditic
- Tegument is highly absorptive
Adults Cestode structure in Final Host
Scolex (head): Suckers, rostellum (neck), hooks (armed)- organs of attachment
Chains of segments “proglatids”. Proglatids combined are strobilia.
Tapeworm segements:
A mature segment has the reproductive organs **(mid body) **
A gravid segment contains eggs only **(tail end) **
Comment on a Taenia gravid segment:
Siegments are continually budded from the neck region. (rostellum)
Organs of sexual reproduction present in mature segment in the mid gut.
These mature segments disappear as the proglattids continue to move posteriorly until the uterus is full of eggs. It is now a **gravid segment. **
Taenia egg: Characteristics
Radially striated egg with a thick egg shell allowing resistance in the environnment.
Hexacanth (6 hooked embryo) a.k.a Oncosphere
Cestode life cycles:
Indirect
FH contains adult tapeworm (often in the SI) and passes out eggs.
IMH ingests eggs, hatch, and larval stage encysts.
FH eats the IMH containing the cyst containing head of future tapeworm
Head of future tapeworm latches on to SI and starts to bud segments.
Cestode larval stages in IMH
Metacestode or larval form
Usually in tissues (encysts)
- cysticercus
- coenorus
- cysticercoid
- hydatid
Family: Taeniidae
FH?
IMH?
Scolex (armed/ unarmed)?
Pathogenic?
- Man, cat, dog S.I.
- IMH: mammal- larval stages encysted.
- Scolex: armed (except for T. saginata)
- Adults relatively non pathogenic
Taenia saginata:
FH?
Armed/ Unarmed?
IMH?
Larval staged encysted in IMH?
FH: man
Unarmed
Cow
Cysticercus bovis: small fluid filled cyst containing a single scolex (head) therefore will give rise to one tapeworm.
Describe the life cycle of Taenia saginata and its PPP?
- Adults in S.I of man
- Pass millions of eggs per day in gravid segments (eggs are resistant, radilly striated, hexacanth 6 hooked)
- Eggs are ingested by susceptible bovine
- Oncophores release is abomasum, penetrate S.I wall
- Travel to skeletal muscle and encysts as Cysticercus bovis (one scolex).
- Takes around 12 weeks for cysts to grow and become infective.
- Meat is ingested by man
- Adults in S.I.
- PPP= 2-3 months
T. saginata Epidemiology:
Inadequate cooking of meat
Eggs long lived
Sanitation
Taenia saginata Diagnoses:
Meat inspection
Tend to encysts in the masster, heart, tongue, intercostal and diaphragm.
How can we control T. saginata?
- Meat inspection
- >25 cysts - CODEMNED
- <25 cysts chill infected carcass at -10 C for 10 days). However if <25 cysts and dispersed all over body then condemn.
- Cooking meat at 57 C. kills cysts
- Restrict use of human sludge to cultivated fields or no cattle grazing for at least 2 years.
- hygiene/ sanitation
Taenia solium:
FH?
IMH?
Larval encysted stage?
Lifecycle?
FH: man
IMH: pig or man
Cysticercus cellulosae
Lifecycle similar to T. saginata
Taenia solium:
Man as IMH?
Man can acts as IMH as well as FH.
Eggs are infective man:
- accidental ingestion of eggs. .
- Auto infection via reverse peristalisis (eggs travel back into stomach, activated, hatch, and spread around body encysting)
T. solium Pathology
Adult tapeworrm = NO PATHOLOGY
It is the encysted larvae which cause pathogenesis. Could be very serious if they encyst in the CNS or eye.
T. solium epidemiology
Close association of man and pig.
Unrestricted access of pigs to human waste.
Poor meat inspection.
T. solium control
- Mass treatment ot kill adults worms in human (albendazole or praziquantal)
- Mass treatment of pigs (oxfendazole)
- Meat inspection
- Pig corralling ( don’t allow pigs to graze on anything they want)
- Vaccination of pigs.
- Don’t allow pigs to graze on human sludge.
- Try to distance areas of human and pig overlap. i.e. don’t allow pig pen close to farm house.
Taenia multiceps:
FH?
IMH?
Larval stage encysts?
FH: dog
IMH: sheep
Coenorus cerebralis
Causes gid in sheep (sheep gait is altered)
Taenia hydatigena:
FH?
IMH?
Larval encysted stage?
Where is this commonly found?
Dog
Sheep
Cysticercus tenuicolis
Commonly in abbatoir: persistant cause of liver condemnation.
Taenia ovis:
FH?
IMH?
Larval encysted stage?
Dog
Sheep
Cysticercus ovis- causes sheep measles
First recombinant vaccine developed against helminth parasite.
Taenia Taeniaeformis:
FH?
IMH?
Larval encysted stage?
Cat
Mouse, rodent
Cysticercus fasciolaris
Dipylidium caninum:
Describe the lifecycle
- Adults in S.I of dog/ cat/ man
- 3 weeks post infection gravid segements shed- active
- Gravid segments ingested by flea/ louse (lice) IMH
- cysticeroid in hemocoel of flea/ louse
- ingestion of flea/ louse by dog/ cat
- PPP= 3 weeks.
Dipylidium caninum IMH:
Fleas- larvae not adults are the IMH because the adult mouthparts of the fleas cannot ingest eggs.
Lice: all stages
Diagnoses of D. Caninum:
- Double genital pore. Pore on each side of the segment.
- Egg packets: not usually eggs in feces: membranous structure with 20+ eggs.
Echinococcus granulosus granulosus
FH?
Site?
IMH?
Zoonosis?
Echinococcus granulosus equinus
FH?
Site?
IMH?
Zoonosis?
E.g.g:
dog, wild canid
SI
ruminants, pig, man
Zoonotic
E.g.e:
dog, red fox
SI
horse, donkey
Not Zoonotic.
Echinococcus adult/ egg characteristics:
Adult: scolex plus 3-4 segments. Very big gravid segment
Egg: Similar to Taenia (radially striated) 6 hook hexacanth
Describe the lifecycle of E.g. granulosus and its PPP?
- Adults in S.I dog
- Gravid segments **shed 1 per week **
- Egg is very resistant.
- Ingested by IMH (pig, man, ruminant)
- Onchosphere released and penetrates the S.I wall of IMH
- Hydatid cysts in IMH liver/ lungs approx 6+ months post infection
- Cysts are ingested by host
- Heads (scolex) erupt from cyst and attach to FH S.I.
- **PPP= 40-50 days. **
Pathology of E.g.g associated with?
Associated with cysts not adult worms.
Comment on hydatid cysts in IMH.
Hydatid cysts can contain thousands of heads “ hydatid sand”
How can we diagnose E. granulosus?
IMH- abbatoir
FH: FEC, Copro-Ag test, Copro-PCR
E. g. granulosus pathogensis:
Mostly well tolerated in the IMH unless cysts in usual site.
Most cases are detected in abbatoir.
Not pathogenic in dog final host.
Always of signifcance in humans.
E. g. granulosis Epidemiology
Domestic?
Sylvatic?
Domestic:
FH: Dog
IMH: Sheep
Dog can infect man
Sylvatic:
FH: wild canid
IMH: ruminant
maintained by predation/ carrion feeding.
E. g. equinus epidemiology
FH: dog/ red fox
IMH: horse/ donkey
Transmitted via equine abbatoirs/ hunting kennels. Maintained by feeding hunting dogs equine viscera.
E. g. granulosis is zoonotic.
Man as IMH?
Man is accidental IMH. Most likely infected by close quarters with infected dog via oncospheres in water, hair, or foodstuffs.
How can we control hydatid disease?
Regular deworming of dogs with praziquantal
Proper disposal of infected carcasses
Deny access of dogs to abbatoirs.
Echinococcus multiocularis:
FH?
IMH?
LIfecycle?
Zoonotic?
FH: dog, cat, wild canid
IMH: rodent, man
Life cycle similar to E. g. g
Zoonotic
Describe the events in E. multiocularis life cycle and its PPP?
- Adults in S.I fox
- Gravid segments shed in feces
- Eggs resistant up to -50 C.
- Ingested by rodent IMH
- Hexacanth released penetrates S.I. Wall
- Travles to liver via Hepatic portal vein. Rapidly vesiculates in the liver.
- Cyst ingested by fox from predation on rodent.
- Scolex erupts from cyst and attaches to fox S.I.
- **PPP= 28-35 days (4-5 weeks) **
Pet passport and Echinococcus multiocularis:
Cat and dogs must be treated for E. multiocularis by dosing with praziquantal 24-48 hours prior to travel in the UK.
Cestodes of the Horse:
Anopolocephala perfoliata
What climates do they prefer?
What pathology do they cause?
Whats a concern/ risk factor in horses due to them?
Characteristics of adults?
high prevalance in temperate climates.
Ulcerations at site of attachements
Risk factor for ileo-cecal colic (ulceration at that junction)
Flat, short segemented.
Describe the events in the lifecyle of Anoplocephala perforliata and its PPP?
- Adults at ileo-cecal junction.
- egg passed in feces
- Ingested by forage mite IMH
- Forms cysticercoid cyst in mite.
- Infected mite ingested by horse when grazing.
- Head emerges from cyst and attaches to gut wall at ileo-cecal junction forming ulceration.
- **PPP= 6-10 weeks. **
A. perfoliata and Colic.
Horses with tapeworms are more likely to suffer colic.
How can we diagnose A. perfoliata in horses?
- FEC: Low sensitivity, high specificity (if test positive then proceed to ELISA.
- ELISA
- Copro- Ag PCR
Egg contains a pyriform apparatus that it sits on. Egg is also mishapen.
