Parasitology Flashcards
(13 cards)
What is Metronidazole? mechanism of action and what eukaryotic parasites does it treat?
Antibiotic used to treat Non-tissue protazoa: (cysts and trophozoites): Amoebiasis [pseudopodia: Entamoeba histolytica (dysentery)], Giardiasis [flagellate: Giardia intestinalis] (watery diarrhoea) , Trichomonas vaginalis.
Inhibits nucleic acid synthesis in anaerobic cells. (interferes with enzyme cysteine residues)
What is Mebendazole? mechanism and what does it treat?
Antihelminth drug: inhibits microtubule synthesis in Nematodes: roundworms, pinworms, hookworms.
How are intestinal (non-tissue) protozoa diagnosed?
Stool sample stained with iodine or trichrome stains
(Entamoeba histolytica [amoebic dysentery] pseudopodia)
(Giardiasis intestinalis, watery diarrhoea [flagellate])
Identify infective cysts or active trophozoites.
Intermediate host and life cycle of tissue protozoan Leishmania donovani? (flagellate tissue protozoan)
Carried by female sandfly (vector)
Promastigotes (flagellate) migrate to proboscis: Injects promastigotes (infective stage) –> into macrophages –> amastigotes multiply inside macrophages and various other host tissues –> may become visceral or cutaneous leishmaniasis
Intermediate host and life cycle of flagellate tissue protozoan Trypanosoma bruceii?
Sleeping sickness (drowsiness/neurological dysfunction)
Tsetse fly:
Infective metacyclic Trypomastigotes injected –> lymphatic system to bloodstream –> bloodstream trypomastigotes replicate by binary fission (and in various other tissues) [always extracellular]
Life cycle of malaria causing parasite: Plasmodium falciparum vs vivax?
intermediate host?
Motile Sporozoites injected by female Anopheles mosquito –> migrate to hepatocytes (where they replicate as schizonts [forming merozoites] and in vivax form hypnozoites [only treatable by Primiquine])
Schizonts/merozoites rupture hepatocytes and spread to RBCs (forming Trophozoites [distinctive ring stage]) (erythrocytic cycle of rupture/reinfection 48-72 hours of fever)
Sometimes form gametocytes which can be ingested by Female anopheles mosquito. (ookinete –> oocyst –> sporozoite)
Differences between Plasmodium falciparum and vivax? treatments?
Vivax: more likely in Asia –> more mild disease but causes recurrence through hypnozoites (so use primiquine [but test for Type A G6PDH deficiency]).
Treat with schizontocides: Chloroquine or quinine or Artesunate. and Primiquine.
Identified by Giemsa smear: Stippled Trophozoite (or schizont)
P.falciparum more likely in Africa: can lead to severe disease and complications like cerebral malaria, renal failure etc.
Treat with Oral Quinine and Doxycycline in uncomplicated. IV if complicated (or IV artesunate)
Identified by Giemsa smear: multiple rings in single RBC, and bean shaped gametocytes.
Physical description and Life cycle of Taenia solium: (a cestode/tapeworm)
Scolex with suckers and hook (no mouth/no GIT)
Hermaphroditic: Mature segments towards end inc. gravid proglottis which bursts to release eggs/oncospheres
Oncospheres ingested by pigs penetrate into GI wall and circulate to muscles –> form cysticerci in muscles –> humans eat undercooked meat –> Asymptomatic or GI symptoms and adult tapeworms.
Dangerous because if humans eat Oncospheres –> Cysticercosis (muscles, brain (seizures), eyes)
Life cycle of Flukes/Trematodes like Schistosoma haematobium? (snails and piss)
Schistosomiasis.
Cercariae released from snail host, free swimming in water –> burrow into human skin (rash/itch) –> lose tails (becoming schistosomulae) –> migrate to liver to mature into adults –> paired adult worms migrate to veins of BLADDER, (in this species) lay eggs into bladder (diagnosis) –> piss eggs into water (?bloody urine, even cancer risk?) –> snails host replicating sporocysts.
Giant roundworms (aka a Nematode, a helminth): life cycle and description? “Ascaris lumbricoides”
Roundworms are most common helminthic infection worldwide. (up to 1/6th asymptomatically infected!!!)
Fully developed digestive tract, adults have 2 sexes.
Live in almost all vertebrates for up to 2 years following ingestion of fertilised eggs from faeces.
Fertilised eggs –> larvae which enter bloodstream and migrate to lungs to mature –> penetrate alveolar walls and ascend airways to be swallowed! –> adult worms sexually reproduce. (can be up to half a metre long…)
Pinworm/threadworm (a type of roundworm/nematode helminth) description and lifecycle, key symptom?
Eggs layed on perianal folds hence itchy anus! (also mode of transmission is scratching –> hands to food, bed linen etc –> mouth –> larvae hatch in small intestine, sexually reproduce and pregnant/gravid female migrates to anus to lay eggs.
Hookworm (a type of roundworm/nematode helminth) infection lifecycle? Description?
Filariform larvae from stools, living in soil burrow into skin. –> circulate in blood –> reach lungs, penetrate, ascend and are swallowed!
Adult worms’ attachment in small intestine leads to blood loss (hooks attach) (iron deficient anaemia)
[Couple of species: differentiated by filariform larvae not eggs.]
