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68 Cards in this Set
- Front
- Back
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What phylum do cestodes and tapeworms belong to?
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Platyhelminths
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What are the 2 main morphological features of cestodes/tapeworms?
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Flat, ribbon like bodies
Alimentary canal |
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What kind of disease can larval cestodes infecting humans cause?
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Cysticercosis
Hydatid disease |
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Where do cestodes cysts form?
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SOFT organs:
Liver, lungs, spleen, BM, muscle, eye, subcutaneous tissue, brain |
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What does disease severity depend on?
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Location of the cyst
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What parasite causes cysticercosis?
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Taenia solium
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What are teh 2 types of cysteicercosis?
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Cystic: dense tissue ~1cm
Rancemose: brain cavities ~8cm |
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What causes hydatid disease?
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Echinococcus multilocularis
-forms multilocular (alveolar) cysts (2-3 mm) Echinococcus granulosus: forms unilocular cyst (25 cm) |
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What disease do Taenia species cause?
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Taeniasis
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What are the different Taenia specis?
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Taenia saginata: beef tapeworm, most common in humans
Taenia solium: pork tapeworm, mort dangerous because it causes cysticercosis |
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What causes Taeniasis?
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Ingestion of cysticerci
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What are the normal symptoms of Taeniasis?
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Abdominal discomfort
chronic indigestion |
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What is the treatment for Taeniasis?
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Praziquantel
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Describe the life cycle of Taenia
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1)Eggs or gravid proglottids in feces and passed into the env't (diagnostic stage)
2) Cattle (T. saginata) and pigs (T. solium) become infected by ingesting vegetation contaminated by eggs or gravid protoglottids 3) Oncospheres hatch, penetrate intestinal wall and circulate to musculature -> Oncospheres develop into cysticerci in muscle (Infective stage) 4) Humans infected by ingestion of raw/undercooked infected meat 5) Scolex of parasite attaches to intestine 6) Adults in small intestine |
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What is a proglottid?
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Full of eggs
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Where is there high prevalence of T. solium infections?
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Latin America
Africa |
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Describe the adult T. solium (more infective/pork) worm
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Scolex with 4 suckers
**Hooks** Extremely long |
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How does the T. saginata differ from T. solium adult worm?
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T. saginata has a scolex with 4 suckers, but NO HOOKS
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What are the suckers and hooks used for?
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Adherence to intestine
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Describe Taenia morphology
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Head-neck ---- immature proglottid ---- mature proglottid
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Know slide 6
What reproductive systems can be seen in the mature segment of Taenia? |
Taenia is hermaphroditic: has both male and female reproductive organs
Mature segment has: Uterus, nerve cord, testes, sperm duct, vagina, ovary |
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Whatis the gravid segment?
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Bag-like uterus filled with Ova
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Why is the gravid segment important for diagnoses?
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Can use it to differentiate between T. saginata and T. solium
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Whats the difference between the gravid segment of T. saginate and T. solium?
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T. saginata is longer, has 15-20 branches
T. solium is shorter, has 7-13 branches |
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Do cestodes have a complete digestive system?
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No, they don't have a mouth or GI tract
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What do cestodes use ensure food uptake?
How does it work? |
Tegument microtriches: ~ host microvilli, increase surface area, acquire nutrients by active transport, pinocytosiis and diffusion
-->This tegument allows active absorption of aa, sugar, vitamin and FA BUT its impermeable to peptides, ptns, macromolec |
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How do cestodes digest?
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Contact digestion: carried by intrinsic and extrinsic digestive enz on microtriches
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What are the 3 fcts that Taenia tegument does?
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Absorptive
Excretory Digestive (doesn't have a GI system) |
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Descibe the Taenia ova
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Spherical
45 um Brownish shell Cannot be used to differentiate between T. saginata and T. solium Contains onchosphere Egg hardy: .: can survive for months in moist soil |
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What happens upon ingestion of ova?
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Cysticercosis
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What are the 3 modes of Taenia infection?
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1) Egg ingestion: drinking water or consumption of raw vegetables/meat
2) Autoinfection: finger to mouth, due to poor personal hygiene 3) Reverse peristalsis of gut content: eggs and proglottids from the small intestine forced into the stomach |
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What happens once hte eggs are in the stomach?
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Pepsin, pancreatic trypsin and bile salt facilitate egg hatching
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What is distinctive of the Taenia embryo?
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Hexacanth embryo (hatched onchosphere) ~30 um in diameter
Ochosphere presents 6 hooks and a pair of secretory glands open laterally |
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What happens once the onchosphere opens?
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Onchosphere anchors to intestinal mucosa
Lyses enterocytes Enter blood vessels in lamina propria enter portal circulation and peripheralize to any part of the body causing cysticercosis |
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What determines the histogenetic fate of the sequestered onchosphere?
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Surrounding host tissue
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Where does the cystic type of cysticercus develop?
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In compact, denser surroundings
-->Muscle, subcutaneous tissues or brain parenchyma (parenchymatous neurocysticercosis) |
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Where does the racemose typse cysticercus develop?
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In subarachnoid space or ventricles of the brain in open spaces (ventricular or meningeal neurocysticercosis)
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Cysteicercus larva
When does the onchosphere differentiate into the cystic form? |
When its in subcutaneous tissue
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Describe the Taenia cyst
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Oval
1X 0.5 cm Invaginated scolex Neck Bladder |
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What does cysticercus secrete? **
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Taeniaestatine ****
Polysulfated polysac |
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What do taeniaestatine and polysulfated polysac do?
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Cover bladder portion blocking inflammation, neutrophil binding and complement activation (anticomplementary)
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What do intaact cysticerci induce?
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Mild inflam .: can survive for years
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What does a ruptured cyst do?
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Release Ag that induce intense tissue inflam, resulting in tissue lysis and edema
Causes clinical symptoms particularly in neurocysticercoses Eventually cysticerci die and become calcified |
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What kind of neurocysticersosis can the different cestode types cause?
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Cystic type: parenchymatous neurocysticercosis
Racemous type: meningeal neurocysticercosis & ventricular neurocysticercosis |
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Where does the cystic type of neurocysticercosis take place?
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In the brain parenchyme
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Where does the racemose type of neurocysticercosis take place?
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Subarachnoid space (meningeal neuro)
Ventricle |
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What are the clinical symptoms of parenchymal cysticercosis dependent on?
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Number of cysticerci, their brain location and viability
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What happens if a few parenchymal cysts are undeteced?
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May causes partial/segmental localized paralysis
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What drugs can be used in this case?
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Albendazole + cortico steroid
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What happens if there is multiple parenchymal cyst?
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Compromis CSF circulation
Increase intracranial pressure -->No treatment recommended |
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Where do onchospheres differentiate into racemose form?
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In hollow locales: Subarachnoid space or Brain ventricles (moving in the host brain tissue)
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Describe the racemose cestode type
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6-10 cm in size
Lacks scolex Grows like a bunch of grapes Cyst fluid very inflammatory ->Incurable when located at the base of the brain |
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What happens if CNS is not involved in cestode infection?
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Subcutaneous: muscle etc
Asymptomatic to mildly symptomatic |
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What happens when the CNS is involved in cestode infection?
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Benign to life threatening outcome
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Describe ventricular/meningeal racemose cysticercoses
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Usually severe
Ruptured cyst, Ag are released and exaggerated inflam and liquefaction necrosis in surrounding tissues Causes meningitis (in arachnoid and piamater) Accumulation of cerbrospinal fluid: cause intracranial hypertension (hydrocephalus: placental tocoplasmose), seizure, blindness Cysticercus at the base of the brain is generally inoperable, with fatal consequences withing 5 years Immunocytochem of brain lesion shows localized inflam around damaged cyst : T cells, Macs, eosino+neutrophils, NK cells, type 1 cytokines |
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How is cysticercus diagnosed?
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Combo of neuroimagng, serology and/or biopsy:
-Computed tomography/magnetic resonace imaging: -Western Blot |
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What does computed tomography/magnetic resonance imaging do?
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Detects space occupying lesions
Cysticercosis included in the differential diagnosis along with tuberculoma, bacterial/fungal abscess/tumor metastasis/congenital cysts |
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What does the Western blot do?
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Highly specific
10 kDa recombinant cysticercus Ag is in use in developing countries to rule out other clinical conditions |
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Describe the immunoreactivity of cysticercus Ag with patient serum
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Reacts with patients actively infected
Does not react with patients Ab if chronically calcified |
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What kind of disease is cysticercosis (region)?
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Mostly rural
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What are the factors that can explain the high incidence of cysticercosis?
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1- Poor sanitation: lack of latrines, inadequate fecal disposal facilities, eegg ingestion and cysticercosis
2- Dietary habits: inadequate boiling of pork products containing cysticerci leads to taeniasis 3- Open air fecalism in rural areas: pigs consume human feces and overtime build up a heavy load of cysticerci 4- Pigs deliberately placed in cout yards to clean up human feces (same result as open air fecalism) |
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What is the only definitive host of T. solium?
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Humans
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Where do adult Taenia live in humans?
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Small intestine
Can live there up to 25 years |
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What kind of infection do adult taenia cause?
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Subclinical infection : rare diarrhea or weight loss
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How do you know if you're infected with adult Taenia?
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Gravid segments found in feces/perianal area
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What happens if humans consume Taenia eggs?
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May lead to generalized cysticercosis or neurocysticercosis
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How can taeniasis be diagnosed?
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Biopsy
Serologic Brain imaging Radiologic |
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How can taeniasis be treated?
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Cysticidal drugs: Praziquantel and Albendazol
Neurocysticercosis: recommended treatment = albendazole (but this can cause strong inflam responses and seizures) Treatment is normally combined with dexamethasone (corticosteroid) because it inhibits the inflam response/edema and inc serum level of albendazol, but decreases praziquantel lvls |
