Flashcards in Parasitology: Helminths Deck (21):
What are the main classifications of helminths?
2. Round worms
-filarial (have juvenile offspring)
What helminths are segmented?
Segmented: tapeworms (cestodes)
Non-Segmented: flukes (trematodes), nematodes
What 2 types of life-cycle do helminths have?
1. direct (1 host)
2. indirect (>1 host)
What is the definitive host?
The organism in which the sexually reproducing parasite reaches sexual maturity.
What is the intermediate host?
The organism in which larval, juvenile or non-sexual stages develop.
Describe the life cycle of Ascrais:
Helminth, fecal-oral, DIRECT
What are the 6 ways in which helminths harm their hosts?
1. mechanical (obstruction/barrier)=Ascaris, Filaria
2. Compete with host for resources= Tapeworms (B12), Hookworm (iron)
3. Cytotoxicity= Flukes (liver fluke)
4. Inflammation= flukes (in blood; Schistosoma--> granuloma)
5. Immune-mediated injury = filaria
6. Malignant transformation = flukes
What is the host response to helminths consistent of?
-effector cell activation w release of cytokines
-macrophages, PMNs, phagocytic cells, NK cells, CTL
-TH2 response necessary to clear intestinal worms (extracellular pathogen)
-eisonophils: degranulate onto IgE-coated worms
What are the hallmarks of immune response to worm infx?
-high circulating IgE
What cytokines to TH2 cells secrete to activate effector cells?
What are the 6 means of helminth diagnosis?
1. direct examination (stool helminths)
2. culture (strongyloides)
3. antigen detection (blood flukes, filaria)
4. host antibody detection (all tissue invasive worms)
5. nucleic acid amplification some tissue invasive worms)
6. radiologic (hydatid cyst, cysticerosis)
What are the 2 medical Rx for helminths?
1. conventional anti-parasitics (all helminths)
2. herbs/plant extracts (pumpkin seeds for tapeworm)
What are the 3 interventional Rx for helminths?
1. percutaneous drainage (hydatid cyst)
2. endoscopic removal (biliary ascaris, intraventricular neurocysticercosis)
3. surgical excision (hydatid cyst, filaria)
What causes Neurocysticercosis?
What is its life cycle?
Taenia solium (larval stage of tapeworm in pork=cysticerci)
helminth, ingestion, indirect
What antiparasitics are used to treat Cysticercosis?
What interventional treatment is used
-Endoscopic removal (from ventricles)
What is the life cycle of cutaneous larva mirgans?
-Helminth, Skin, penetration INDIRECT
What is the treatment for cutaneous larva migrans?
What is the worm that crawls across the eyeball?
(a type of filariasis, roundworm/nematode)
What is the life cycle of Loa loa?
Helminth, vector-borne, INDIRECT
What condition is caused by Loaisis infection?
Elephantiasis due to lymphatic filariasis (mechanical obstruction of lymphatics)