10 - Parasitology: 1 Flashcards
(43 cards)
What is parasitism?
Beneficial for one, harmful for the other.
What is a parasite? What are the two main types?
Organism that feeds and grows in or on a host organism to the detriment of that host.
Ectoparasites: infestation on or tiwhtin the skin; usually arthropods
Endoparasites: infection inside the body; protozoans (unicellular) and helminths (multicellular worms).
What is a definitive host? What is an intermediate host? What are examples?
Harbors sexual stage of a parasite’s life cycle. We are the hosts for schistosoma.
Intermediate host: supports asexual reproduction or development of a parasite intermediate host for schistosoma is snails.
What is an incidental host? What is a reservoir host? What are examples?
Incidental: dead end host; not necessary to close the life cycle of the parasite. (humans for toxoplasma)
Reservoir: an animal species that maintains the parasite’s life cycle in the wild. (mice for toxoplasma.
What is a vector?
A host species that transmits infectious parasite to another host.
What is incidence? What is prevalence?
Incidence: The number of NEW cases of a disease in a given population that develop in a given period of time.
Prevalence: number or proportion of cases of a disease in a given population at a specific time
When do domestic physicians need to consider parasites as a cause of disease? What should they do when its suspected?
- Pts traveling abroad
- Pts born in endemic areas
- Pts with compromised immune systems due to steroid use, cancer therapy, transplant meds, AIDs, or advanced age.
Consult infectious disease specialist and obtain current information from the CDC hotline.
Worm infections typically involve ______ and elicit a ____ response. What do protozoan parasites elicit?
Worm: Eosinophilia and elicit a Th2 response.
Protozoan: Th1 response
What is a biological obstacle during development of parasites? How does development play into this?
They are eukaryotes and use many of the same basic molecular pathways as their human host.
Flat and round worms are in the same kingdom as humans; this makes them harder to target and treat.
What is an egg? What is a larva?
Egg: product of sexual reproduction that contains embryonated pre-larval form
Larva: immature post-ovum (pre-adult) form
what is a cyst? What is a cysticeri?
Cyst: dormant stage encapsulated in host tissues
Cyticerici: encysted cestode larvae in tissues of intermediate host (found in pork tapeworm in humans).
What is a hydatid cyst?
Specialized cysticercal form of Echinococcus granulosus in intermediate host.
What are the two classes of the phylum of flatforms - ie Platyhelmintes?
Class Cestoda
Class trematoda
What are the characteristics of the class cestoda of the platyhelminths?
Hermaphroditic tapeworms with flattened, segmented bodies.
No digestive system, absorbed through tegument
Anterior end (scolex) attaches to definitive host intestine wall. Segments (proglottids) mature anterior to posterior.
Transmission by ingestion of eggs or cysticerci.
What are the characteristics of the class trematoda? What is the main type we are concerned with?
Schistosoma - has both male and femal
Unsegmented
simple, blind digestive system
One or more intermediate host (snail)
invasive (penetrate skin)
What organisms are in the class cestoda?
- Teania saginata
- Taenia solium
- Diphyllobothrium latum
- Echinococcus granulosus
What organisms are in the class trematda?
schistosoma (blood flukes)
What is the life cycle of Taenia saginata and taenia solium?
- Eggs or proglottics in feces are passed into environemtn.
- Cattle (saginata) and pigs (solium) infected via ingestion
- Eggs hatch and penetrate intestinal wall and circulate to musculature
- Larva develop into cysticerci in muscle of cow or pig
- Humans eat raw or undercooked meat and scolex attached to intestine.
How does the scolex and proglottid differ in taenia saginata and solium?
Taenia saginata: four suction cups on scolex; branching proglottid.
Solium: ring of spikes in center of scolex; less branching proglottid.
How can the life cycle of taenia solium (pork tapeworm) differ from the one previously described? Ie why is it important to distinguish one from the other in treatment.
Its eggs can also infect humans and humans can be the intermediate host.
Larva will form cysticeri that can develop in any organ including the brain and eyes.
Much more dangerous.
How is taenia solium transmitted? What are the two ways it can develop (ie what is the names of the illnesses)?
Through ingested of undercooked cork with cysticeri - grows into tape worm in intestine - called taeniasis
Cysticeri can form in muscle, brain, and eyes - called cysticercosis.
Both forms can occur in the same person.
What are the symptoms of Taeniasis? What are the symptoms of Cysticercosis?
Taeniasis: usually asymptomatic, may cause abdominal pain,nausea, weight loss. Can still infect others.
Cysticercosis: cysts in muscle typically asymptomatic; may cause lumps. Cysts in brain can cause headaches, seizures, cunfusion, impaired balance, swelling, stroke, and death.
How would you diagnosis Taeniasis? What about Cysticercosis? How would you treat them?
Taeniasis: see proglottids or eggs in stool.
Cysticercosis: X ray to see dead calcified larvae or cysticerci on CT/MRI.
Praziquantel, niclosamide, or albendazole (single dose for adult worm or prolonged treatment for cysticerci). Also need steroids to reduce inflammation.
What is the life cycle of Diphyllobothrium latum (fish tapeworm)?
- Unembryonated eggs passed in feces and eggs embryonate in water
- Coracidia hatch from eggs and injested by crustaceans and larva grow in body of it
- Small fish eats crustacean; Big fish eats small fish; we eat big fish
- humans ingest raw or undercooked infected fish; grow to adults in small intestine where proglottids release immature eggs
