10/14/2009
Beef Wellington
Helminths
• Phylum Nematoda (Roundworms) - “Nematodes”
• Phylum Platyhelminthes (Flatworms)
(Fl t )
– Class Cestoidea (segmented flatworms) -
“Cestodes”
– Class Trematoda (non-segmented flatworms) -
“Trematodes”
Cestodes Adult Taenia saginata
All members are flat, segmented worms and are
obligate parasites of the intestinal tract.
Mature proglottids
Scolex
The tapeworms:
Taenia saginata (beef tapeworm) Immature proglottids
Taenia solium (pork tapeworm) Gravid proglottids
---> Cysticercosis
Echinococcus granulosus (dog tapeworm)
---> Hydatid Disease
cm scale
Taenia saginata scolex
Suckers
Taenia saginata
The beef tapeworm
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Taenia Adult
Embryonated, infectious taeniid eggs
Hexacanth larva Hooklets
Egg shell
Cannot distinguish species of Taenia tapeworms
based on morphology of eggs
Pathogenesis:
None
Gravid Proglottid of Taenia saginata
Uterine branches
Uterus
The central uterus of T. saginata has more than 12 branches on a side
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Prevention and Control:
1. Sanitary disposal of feces
Clinical Disease:
N
None iin h
humans
Prevention and Control
Diagnosis: (cont’d):
1. Find eggs on sticky tape test 2. Prevent cows from coming into contact with
or in stool human feces - maintain good
sanitary
it practices.
ti
2. Identify species based on proglottid 3. Freeze and/or cook all beef until well-done
morphology (Good luck, NY!!).
4. Federal meat inspection programs work.
Drug of Choice: Taenia solium
Praziquantel The Pork Tapeworm
O C
N
N O
Mode of Action:
Interferes with invertebrate Ca 2+ ion channels
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Adult Taenia solium
Embryonated, infectious taeniid eggs
Hexacanth larva Hooklets
Scolex
Egg shell
Cannot determine the species of Taenia based on egg morphology
Taenia solium scolex
Hooks
Suckers
Photo: E. Grave
Gravid proglottid Taenia solium Whole cysticercus of Taenia solium
Uterine branches number less than 10 per side
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Drug of Choice:
Praziquantel
Pathogenesis: O C
N
None N O
Mode of Action:
Interferes with invertebrate Ca 2+ ion channels
Prevention and Control:
1. Sanitary disposal of feces
Clinical Disease:
None
Prevention and Control
Diagnosis: (cont’d):
1. Find eggs on sticky tape test
2. Good sanitary practices on the pig farm.
or in stool
3. Cook and/or freeze pork products thoroughly.
2. Identify species based on proglottid
4. Federal meat inspection is effective.
morphology
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Cysticercus floating freely
in anterior chamber
Cestode hosts
T. saginata T. solium
Definitive Host: Human Human
Intermediate Host: Cow Pig Parasite
Human
Cysticercosis and
Neurocysticercosis Cross section of eye with cysticercus near optic
nerve. Disease was mis-diagnosed as retinoblastoma.
Multiple Intracerebral Cysts
Cysticercus
“Alien”
Radiogram of lower leg with numerous
calcified cystercerci of T. solium
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Cysticercus in brain, on post-mortem pathology
Subcutaneous Cysts
Asymptomatic cyst; cause of death, mesothelioma
Neurocysticercosis
Neurocysticercosis
of the spine
T1 weighted T1 with contrast T2 weighted
Cerebello-pontine angle
Neurocysticercosis
cysticercus
This may cause hydrocephalus CT Scan MRI
MRI sagittal and axial views with flare
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Global distribution of Taenia solium cysticercosis/taeniosis
Intracerebral Calcifications
High prevalence
Moderate prevalence
Low prevalence (imported cases)
No information available/no evidence
How bad can things get? Clinical Epidemiology of
Cysticercosis
• Mexico, South America, Sub-saharan Africa, India,
and Southeast Asia
• Est. 50 million people with Intestinal Taeniasis, world-
wide
• 2% - 7 % have neurocysticercosis
• Leading cause of adult-onset seizures worldwide
(~40%)
– Remainding causes are trauma, TB, tumors, toxins, other.
• In US: Est. 1000 new cases per year (no mandatory
report)
– Immigrants account for ~ 95% annually
– Travelers account for 3%-5%
– Autochthonous transmission: rare
Immunomodulation
Pathogenesis:
• Taeniastatin: protease inhibitor
• Paromycin Space-Occupying lesion
– Inhibits complement
• Other proteases: Local Immunologic Reaction
– Degrade IL-2, immunoglobulins and
interferon
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Echinococcus granulosus
Clinical Disease: The Dog tapeworm
Hydatid Disease in Humans
1. Vision impairment / Blindness
2. Seizures / Death
3. Hydrocephalus / Coma / Death
4. Neurological deficits, dependent upon
location
Diagnosis:
Must differentiate between cysticercosis and
other possible lesions (benign cysts, solid
Cestode hosts
tumors, etc.)
T. saginata T. solium Echinococcus
granulosus
p y whenever p
1. Biopsy possible Definitive Host: Human Human Dog
2. Physical (palpation) and radiological Intermediate Host: Cow Pig Sheep
evidence
Human Human
3. ELISA-based serological tests
4. MRI
Treatments: Traditional farming practices help to maintain
the cycle in animals and humans.
1. Surgical removal of cysticercus whenever possible
2. Steroids (e.g., dexamethazone) during time of
neurological symptoms
3. Anticonvulsants (Dilantin)
4. Praziquantel or albendazole plus steroids
if multiple symptomatic cysticerci are inoperable
Navaho, Arizona Abattoir, Ecuador
(still being studied)
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Adult of Echinococcus granulosus
Hydatid Cyst diagram
Mature proglottid
Gravid proglottid Scolex with suckers
and hooks
Radiogram of upper body showing elevation in
right lobe of liver due to large hydatid cyst
Hydatid cyst of Liver Distribution of Hydatid cysts
Liver - 63%
Lungs - 25%
Muscles - 5%
Bone marrow - 3% (usually fatal)
Kidney - 2%
Spleen - 1%
Brain - 1% (usually fatal)
Visualize: Hydatid cyst, daughter cysts, hydatid fluid
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Petri dish filled with daughter cysts of
Hydatid cyst of Parietal Lobe Echinococcus granulosus
Pathogenesis and Clinical Histological section through brood
disease: capsules in hydatid cyst of Echinococcus
granulosus
1. Hydatid cyst per se is not a problem as a
single cyst in liver, while it is
immunologically
silent.
2. In other organs (e.g., brain, lung, bone
marrow), an hydatid cyst may range
from asymptomatic to fatal, depending on its
effect as a space- occupying
lesion or if ruptures.
3. If it ruptures however, no matter which organ
it occupies anaphylaxis usually
Liver infected with hydatid cyst of Brood capsule with protoscolices of
Echinococcus granulosus Echinococcus granulosus
CT Scan Ultrasound
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“Hydatid sand”
Drug of Choice:
Albendazole
Mode of Action:
De-polymerizes invertebrate microtubules, only
Diagnosis: Prevention and Control:
A. Direct
1. DO NOT BIOPSY! 1. Regularly treat all dogs with niclosamide that
2. Detect circulating antigens have contact with sheep. This drug
3. Microscopic examination of fluid from hydatid kills the adult parasites.
cyst after surgical removal
removal, see
“hydatid sand”
2. Avoid feeding hydatid cyst material to dogs.
B. Indirect
1. ELISA-based serology 3. Public health education of sheep farmers.
2. MRI, CAT, x-ray
3. Accurate case history (ownership of dogs,
living on a farm, etc.)
Treatment:
• Surgical, whenever possible
• Pharmacologic has less than 50%
success
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