17c Parasites (Worm Infections) Duncan Flashcards
What is some general information on worm infections?
Very prevalent throughout the world; though less so in the US. Diseases can range from relatively innocuous (lethargy) to severly debilitating. Fecal oral route, inadequately cooked food, direct attack on skin, transmitted by vector
What are the three main classes of worms that cause infection?
Nematodes (roundworms: ENTEROBIUS, Filaria (causes Filarial elephatiasis)). Cestodes (flatworms or tapeworms). Trematodes (flukes)
What is usually indicative of a helminthic infection?
Eosinophilia
What is the unique treatment for Filariasis?
Antibiotics such as tetracycline. Rationale: worms causing lymphatic filariasis contain an endosymbiotic bacteria required for viability; killing the bacteria is sufficient to kill the worm
What is Dracunculiasis?
From drinking copepod contaminated water. Dracuncula larvae released in stomach. Migrate to connective tissue; fertilization. Migrate to limbs, and produce ulcerous vesicle. Skin breaks; new baby worms released into water
What are the 3 main types of agents used for Helminthic infections?
Benzimidazoles (Mebendazole, thiabendazole, albendazole. Usually very effective against Nematodes). Modulators of neuromuscular function (Pyrantel pamoate, etc. Primarily acts to paralyze the worm, allowing the body to expel them). Miscellaneous - Niclosamide
What are some important structural features of Benzimidazoles?
1) Benzimidazole plus R groups attached to both parts. 2) Albendazole quite similar to mebendazole. 3) Thiabendazole has sulfur-containing heterocycle attached to imidazole
What is the MOA of Benzimidazoles?
Disruption of Microtubules; and blockage of their functions: chromosome movement/cell division, cell motility, internal cell skeleton, intracellular movements, glucose transport (glycogen depletion). Benzimidazoles bind to B-tubulin
How do Anti-worm agents that affect neuromuscular activity work?
Hyperpolarizing the membrane. Permanently depolarizing the membrane. Inhibiting acetylcholinesterase (ACE-I)
What is this structure?
Neuromuscular activity modulator. MOA: Depolarizes neuromuscular junctions; spastic paralysis; ACEI
What are the important structural features of Pyrantel Pamoate?
1) Two part structure; not covalently bonded. Pyrantel is the active part. Pamoate promotes intestinal localization - insoluble
What is this structure?
Neuromuscular activity modulator. MOA: Increases neuromuscular junction activity, disruption of cell membranes; immunse response. Works against Cestodes, Trematodes, Flukes
What are the important structural features of Praziquantel?
1) Nucleus structurally related to pyrazinoisquinoline. 2) R group is benzoid acid
What is the preferred agent for Onchocerciasis (from Filaria, nematode)?
Ivermectin (Mectizan)
What is this structure?
Neural activity modulator. MOA: Increased activity of glutamate Cl channels, unique to worms (invertebrates). This is a unique form of 16 membered lactone ring system
