Cestoda Summary for medical parasitology, Geographical distribution Hosts Mode of transmission Diagnosis Treatment

1. Summary

2. Cestodes Geographical Distribution
T. solium worldwide
T. saginata worldwide
D. latum Circumpolar regions
D. caninum Worldwide
H. Nana Worldwide most common cestode in north America
H. Diminuta Worldwide
Echinococcus granulosa Worldwide
Echinococcus multicularis Northern hemispheres
Geographical Distribution:
HABITAT FOR ALL IS: SMALL INTESTINE
Except: echinococcis and cystocercosis
(TISSUE CESTODES)

3. Species D.H. I.H. I.S D.S.
T. solium Human the only one Pigs Cysticercus cellulosae (Larva) Eggs
Gravid segmints
T. saginata Human the only one Cattle Cysticercus bovis (Larva) Eggs
Gravid segmints
D. latum Human 1st: cyclops or
craustacean
2nd: fish
Pleocercoid (Larva) Eggs
Gravid segmints
D. caninum Dogs or accidentaly human Flea or lice eats
cystecercoid larva
cystecercoid (Larva) ingested
by D.H from I.H
Eggs
Gravid segmints
H. Nana
(Indirect cycle)
Human & Rodents Flea or Grain Beetles cystecercoid (Larva) ingested
by D.H from I.H
Eggs
Gravid segmints
H. Nana
(direct cycle)
Human & Rodents Human & Rodents Emberyonated Eggs Eggs
Gravid segmints
H. diminuta Human & Rodents Many arthropod
especially Tribolium
cystecercoid (Larva) ingested
by D.H from I.H
Eggs
Gravid segmints
Echinococcus Dogs (E.granulosus/multilocularis)
Fox (E. multilocularis)
Human and sheep Eggs Hydated cyst materials ,
hydated sand, hooklets
Cystocercosis Human Human or pigs Eggs Cysticercus cellulosae in
tissue
Hosts:

4. Cestode Mode of Transmission
T. solium Ingesion of improperly cooked pork containing Cysticercus cellulosae
Cystocercosis Heteroinfection: Ingestion of contaminated food or water with T.solium eggs
External autoinfection: using contaminated hands with eggs to mouth for eating (feco-oral)
Internal autoinfection: reversal of peristalisis carry eggs to stomach causing reinfection.
T. saginata Ingesion of improperly cooked beef containing Cysticercus bovis
D. latum Ingestion of raw or undercooked fish containing pleocercoid larva
D. caninum Accidental direct ingestion of flea or lice containing cystecercoid larva or ingesion of food them
H. Nana
(Indirect cycle)
Accidental direct ingestion of Flea or Grain Beetles containing cystecercoid larva or ingesion of food containg them
H. Nana
(direct cycle)
Heteroinfection: Ingestion of contaminated food or water with H.nana eggs
External autoinfection: using contaminated hands with eggs to mouth for eating (feco-oral)
Internal autoinfection: the eggs release their hexacanth embryo, which penetrates the villus continuing the infective
cycle without passage through the external environment
H. diminuta Accidental direct ingestion of arthropod containing cystecercoid larva or ingesion of food containg them
Echinococcus 1- Ingestion of contaminated food or drink with Echinococcus granulosus/multilocularis egg from infected dog feces. (or
fox in case E. multilocularis)
2- Handling or playing with infected dogs (egg contaminates dog's hair) (or fox in case E. multilocularis)
3- Lesions distribution: 70% liver, 20% lung, 10% brain and bones
Mode of Transmission:
N.B: H. Nana cas cause internal autoinfection persists for life

5. Cestode Main Diagnosis
D. latum, D. caninum, taeniasis, H.nana, H.diminuta Coproscopy:
Eggs and/or gravid segments (proglottids)
Diagnosis:

6. Cestode Main Diagnosis Comments
Cystocercosis • History : Most common seizures + Increased ICP symptoms + epidemiology
• Examination: Fundoscopy showing parasite is pathognomonic for ophthalmic
lesions.
• CT scan: Calcifications and parenchymal cysticerci in NCC. Also useful for
diagnosis of cysticercal involvement of the eye and orbits. "cigar-shaped
calcifications” in non-NCC lesions.
• MRI: For detecting relatively small lesions, intraventricular and subarachnoid
lesions in NCC. Cystic or enhanced lesions.
• Serology: Test of choice is enzyme-linked immunoelectrotransfer blot (EITB) using
parasite glycoproteins performed on serum. Monoclonal antibody-based antigen-
detection assays can aid in the diagnosis. (These tests are commercially available
in Europe)
• Histopatology: rarely used.
• ELISAs using unfractionated antigens should not be used, as
these have performed poorly in comparative studies (both
false-positive and false-negative results) and due to poor
sensitivity and specificity.
• Testing serum for serology is generally more sensitive than
CSF
• In patients with multiple lesions, the sensitivity of serum EITB
is nearly 100 percent. However, in patients with a single lesion
or calcifications only, the sensitivity is poor.
• -VE serology do not exclude the diagnosis of NCC in patients
with compatible clinical and radiographic findings. In addition,
for individuals from endemic areas, +VE serology may reflect
previous infection and/or extraneural cysticercosis
Hydated cyst • Nonspecific ↓ WBC or PLT, mild eosinophilia, and nonspecific abnormal LFT
• US: Sensitivity is 90-95%. most common appearance is an anechoic, smooth,
round cyst. Other: water lily signs, car wheel (eggshell) signs. hydatid sand sign
when shifting the patient while doing US.
• CT Scan: Sensitivity 95-100%, the best for determining the number, size, &
anatomic location of the cysts.
• Serology: Useful for primary diagnosis and for follow-up. ELISA is most sensitive
and specific of the available assays. (see next slide). Two major E.
granulosus antigens used in serology include antigen 5 and antigen B.
• Antigen assays: Latex agglutination or a dot-ELISA to detect echinococcal antigens
from cyst fluid have excellent sensitivity and specificity.
• Cyst aspiration or surgical removal: percutaneous aspiration or biopsy confirm
the diagnosis by demonstrating the presence of protoscolices, hooklets, or
hydatid membranes.
• Eosinophilia is observed in fewer than 15 %
• CT scan also used for monitoring lesions during therapy and to
detect recurrences.
• CT > US for detection of extrahepatic cysts.
• In serology, lack of standardization, various methods of
antigen isolation and purification and use of same methods in
clinical settings & epidemiological studies, influence the rates
of false-positive and false-negative serologic results
• A negative serologic test generally does not rule out
echinococcosis.
• False-positive reactions are more likely in the presence of
other helminth infections (such as Taenia saginata, Taenia
solium, and particularly neurocysticercosis), cancer, and
immune disorders.
Diagnosis: NCC = Neuorcystocercosis

8. Treatment:
Cestode Treatment Comments
T. saginata/T.
solium/D. latum/D.
caninum/H. Diminuta
• Drug of choice: Praziquantel 5-10 mg/kg PO
• Alternative: Niclosamide 2 g PO once
• Avoid praziquantel in and niclosamide in T.solium as it induce
cystocetcosis. Ask Prof
• Use quincrine HCL + antiemetic for T.solium
H. Nana • Drug of choice: Praziquantel 25 mg/kg PO
• Alternative: Niclosamide 2 g PO for 7 days
• Repeat the dose after 2-3 weeks because the drug will kill
the adults only. To avoid autoinfection.
• Treat the family
Echinococcus
granulosa
• Surgical cyst removal
• Cyst aspiration (PAIR therapy =percutaneous
aspiration injection of conc. salt solution or
alcohol (1 min only) , re-aspirate, Inject saline.
Repeated every 2 weeks until germinal layer die
(up to 15 times).
• Praziqantel for 15 days and albendazole for 4
weeks repeated every other month Ask Prof
• Albendazole 15 mg/kg/d (max 800 mg) PO in 2 doses x >2 yrs
(from PDF)
Cystocercosis • Albendazole (15 mg/kg/day) combined with
praziquantel (50 mg/kg/day) for 10–14.
• Corticosteroids if inflammation is present
• Antiepileptic medications
• MRI be repeated at least every 6 months until resolution of
the cystic component
• Read IDSA guidelines.

9. UPTODATE (TAPEWORM INFECTIONS)
For successful treatment, the scolex must be destroyed and eliminated; a residual scolex can result in
regrowth of the entire tapeworm. After treatment, the proximal parts of the tapeworms disintegrate, and
gravid proglottids can release eggs as they are being destroyed. Because praziquantel kills adult worms
but not eggs, precautions should be taken to prevent autoinfection, laboratory-acquired infection, or
dissemination to others. With large tapeworms, such as Taenia and Diphyllobothrium species, intact or
disintegrating segments and eggs may be passed for several days. Following therapy, stools should be
rechecked for eggs at one month (hymenolepiasis or diphyllobothriasis) or three months (taeniasis) to
document cure.