0529 - Parasites Flashcards
What’s the difference between definitive, intermediate, and paratenic hosts?
Definitive Host - parasite reaches sexual maturity
Intermediate - Development occurs, and non-sexual reproduction may occur, but no sexual maturity.
Paratenic - Development, but no sexual maturity - waits to get eaten by another host.
What is a reservoir for parasites? Vector? Zoonosis?
Reservoir (transport) - Animal that can be normally infected with a parasite that may also infect humans
Vector - Carrier animal that transports parasite from one host to another
Zoonosis - Disease or infection naturally transmitted between vertebrates that may thus transmit to humans.
Why are lice a clinically significant parasite?
Can carry other organisms with them - rikettsia, trench fever, typhus.
Why are ticks a clinically significant parasite?
Significant vectors of infectious agents (viral, rickettsial, bacterial, or protozoal), some of which may cause paralysis.
Need a blood meal before they can moult and undertake nexst stage of life cycle (larvae->nymph, nymph-> adult, adult->laying eggs).
What is Toxoplasma Gondii (epi, location/disease, definitive host).
Obligate intracellular parasite, acquired by eating poorly-cooked meat. 20% of 20yo and 40% of 40yo seropositive.
Lifetime infection develops in all body organs, particularly muscles and CNS, but asymptomatic in immunocompetent hosts. Catastrophic impact in prenatal infection (tachyzoites can cross placenta), particularly in first trimester.
Reproduces in cats.
What is Taenia solium?
Pork tapeworm - Humans can be both definitive and intermediate host. Can encyst into brain, causing potential death.
Briefly outline Echinococcus Granulosus (Epidemiology, disease, treatment)
Only echinococcus that occurs in Australia.
Intermediate stage infects people, causing massive morbidity and potentially mortality.
Generally found in liver, sometimes lungs, occasionally anywhere.
Treated by major surgery, albendazole, or PAIR - Puncture, Aspirate, Inject (something to kill them), Reaspirate.
What is the life cycle of Echinococcus Granulosis?
Two distinct forms - Eggs excreted by dogs/dingos (definitive host), eaten by sheep (intermediate host).
In sheep - Oncosphere hatches and extravates through gut wall. Migrates to, and form cysts in liver and lungs. These are the first organs eaten by predator dingoes/dogs.
In Carnivores - Ingest liver or lungs of prey. Cyst ruptures, releasing protoscolex, which matures into scolex and becomes an adult in the small intestine. Eggs are then excreted in the feces. There’s a true reservoir of transmission.
