Exam 3: Lect 1 Flashcards
Obligate parasite
A parasite that must always live in contact with a host
Facultative parasite
A parasite that can complete its life cycle in a free-living environment or, alternatively, that lives during part or all of its cycle within a host
Endoparasite
Living within a host (ex. tape worms, malaria)
Ectoparasite
Living outside the host (body surface) (ex. Fleas, lice, mites)
Adult Helminthic Replication
Dioecious
- Male reproductive organs are in one individual, and female reproductive organs are in another.
- Reproduction occurs only when two adults of teh opposite sex are present in the same host
Adult Helminthic Replication
Monoecious or hermaphroditic
- One worm has both male and female reproductive organs and may self-fertilize
- Two hermaphrodites may copulate and simultaneously fertilize each other
Classification of human parasites
Sucker
Attachment organ, adhesion to host tissue
Classification of human parasites
Scolex
The head or attachment portion of a tapeworm; suckers or hooklets are present
Classification of human parasites
Hooklet or rostellum
Top of the head portion of the tapeworm bearing hooks
Classification of human parasites
Operculum
Egg cap of parasitic larvae
Classification of human parasites
Proglottid
Tapeworm segments containing male and felmale reproductive systems; may be immature, mature, or gravid
Classification of human parasites: Proglottid
Definition of “Gravid”
uterine branches filled with eggs
Classification of human parasites
Ventral
Pertaining to the front or anterior
Classification of human parasites
Dorsal
Back side
Classification of parasitic worms
Trematodes (flukes): Intestinal
Fasciolopsis
Classification of parasitic worms
Trematodes (flukes): Liver and lung
Clonorchis (Opisthorchis) Paragonimus
Classification of parasitic worms
Trematodes (flukes): Blood
Schistosoma
Classification of parasitic worms
Cestodes (tapeworms): Intestinal
Diphyllobothrium, Taenia
Classification of parasitic worms
Cestodes (tapeworms): Tissue (larval form)
Taenia, Echinococcus
Classification of parasitic worms
Nematodes (roundworms): Intestinal
Ascaris, Enterobius
Classification of parasitic worms
Nematodes (roundworms): Tissue
Trichinella, Toxocara
Classification of parasitic worms
Nematodes (roundworms): Blood and Tissue
Wucheria, Loa
Antihemintic treatment
Class: Benzimdazoles
- Albendazole, mebendazole
- Oral administration
- Mode of action: Binds to nematode beta-tubulin, inhibiting polymerization and preventing the formation of microtubules, stopping cell division. Impaired uptake of glucose, leading to depletion of glycogen, and reduced stores of ATP
- Can stimulate Ascaris worms to emerge from mouth and nostrils, patients should be forewarned
Mode of action: Bezimidazoles
- Binds to nematode beta-tubulin, inhibiting polymerization and preventing the formation of microtubules, stopping cell division. Impaired uptake of glucose, leading to depletion of glycogen, and reduced stores of ATP
- Can stimulate Ascaris worms to emerge from mouth and nostrils, patients should be forewarned
Antihelmintic treatment
Class: Pyrazinosoquinolones
- Praziquantel
- Oral
- Mode of action: Disrupts calcium ion homeostasis in the worm, antagonizing voltage-gated calcium channels resulting in uncontrolled calcium ion influx leading to uncontrolled muscle contraction and paralysis exposing schistosome antigens at the parasite surface
- The binding site for the drug remains to be identified
Mode of action: Pyrazinosoquinolones
- Disrupts calcium ion homeostasis in the worm, antagonizing voltage-gated calcium channels resulting in uncontrolled calcium ion influx leading to uncontrolled muscle contraction and paralysis exposing schistosome antigens at the parasite surface
- The binding site for the drug remains to be identified
Antihelminitic treament
Class: Macrocyclic lactones
- Ivermectin, doramectin
- Topical, oral or possible
- Mode of action: Binds to glutamate-activated chloride channels existing in nerve or muscle cells of nematode causing hyperpolarization of nerve or muscle cells by increasing permeability of chloride ion through the cell membrane, parasites are paralyzed to death
- Toxicity: May cause neurotoxicity
