Parasitology Flashcards

Question

Why can't all anopheles spp. Transmit malaria?

Answer 1

The parasite might not develop inside the mosquito | It's behaviour, biting preferences etc. Preclude the mosquito becoming infected

Answer 2

It is female anopheles 7 mm Take blood meal only 3 times in life Proboscis- it injects anticoagulant into the blood to suck blood more effectively

Answer 3

Infection is transmitted through bite by anopheles Mosquito carries sporozoites in saliva so injected she insect takes a blood meal The sporozoites enter the blood stream and quickly migrate to the liver where they use surface proteins to attach to hepatocytes (CSP) They multiply exponentially to produce many schizonts (collection of merozoites- nucleus surrounded by cytoplasm) Eventually hepatocyte bursts releasing the merozoites into the blood stream P.vivax and P. Malariae - some sporozoites take a dormant form in the liver and reactivate months or a year later Has specific surface proteins (MSPs) which allow attachment to glycoproteins on RBC membrane Each merozoites develops into the ring form Trophozoite Inside the RBC plasmodium grows As it is a eukaryote it produces its own proteins Parasite proteins expressed on the surface of RBC called knobs The trophozoites feed on Hb grow and divide to form schizonts which contain more merozoites The break down product of this metabolism is called - haeomozoin (malaria pigment) Burst out of the RBC and infects new RBC The plasmodium parasites hide in the liver cells and RBC so immune system won't detect Infect RBC move around systemic circulation Can get stuck in small blood vessels due to knobs e.g. In the brain Reduction of nutrients in host blood (maybe) - Trophozoites develop into gametocytes instead of more merozoites Gametocytes is taken up when host is bitten (take up male and female gamete- continue cycle) The gametes fuse in mosquito gut to form zygote - ookinete - invade mosquito gut wall where it forms oocyte Grows - form sporozoites Oocyte bursts - sporozoites released into Mosquitos body and enter salivary gland

Answer 4

Circumsporozoite protein

Answer 5

At different life cycle stages the parasite expresses different cell surface antigens By the time the host had made a suitable antibody the parasite has moved on to the next stage One parasite can produce vast numbers of progeny so immune system cannot respond adequately

Answer 6

Asexual- human host | Sexual- mosquito host

Answer 7

Blood giemsa stain Thick - release parasites Think - stay in the cell, can find out what species it is

Answer 8

Merozoites surface proteins enable attachment of glycoproteins on red blood cell membrane

Answer 9

``` Worms Large compared to Protozoa and prokaryotes Relatively complex Life cycle - changes in morphology Sexual reproduction - production of eggs ```

Answer 10

GI tract muscle of secondary host, soil, water, skin, eyes

Answer 11

Ph, temperature (they have enzymes), need a host as part of life cycle

Answer 12

Roundworms - Ancylostoma duodenalis, Necator americanus (Nematoda) Tapeworms - beef tapeworm - Taenia saginata (Cestoda) Flukes - liver fluke (fasciola hepatica) - common infection in sheep (Trematoda)

Answer 13

Ancylostoma duodenale ‘Old World’ hookworm, Although now found throughout the world including N and S America and Caribbean Necator americanus ‘New World ‘ hookworm, Accounts for 95% hookworm infections in US, but also found in Africa and South East Asia

Answer 14

Infection acquired when larval worm in contaminated soil burrows through skin (usually base of foot) Eventually leads to severe and chronic anaemia

Answer 15

Infective larvae found in contaminated soil Penetrate host’s skin , enter small blood vessels and thus main circulation Larvae travel to the heart, through the cardiac blood supply to the lungs Coughed up and swallowed Enter intestinal tract and migrate to small intestine In small intestine, grow in size and develop into mature adult worms Adult female worms up to 15mm long and males about 10mm Attach to gut wall using their sharp ‘teeth’ and suck membrane and blood from the host’s blood vessels Produces an anticoagulant to reduce clotting of host’s blood At least half of the blood taken in passes through the worm’s digestive tract but is not metabolised and passes out again undigested So worm has to continually feed and continually migrate to fresh sites on the host’s intestinal wall Adult worms can live for 10 years inside their hosts if undetected Cause severe anaemia, due to the blood ingested by the worm and bleeding at ‘old’ sucking sites Usually each host is infected with more than one worm If male and female present, they mate Female produces fertile eggs, each containing a ‘rhabditiform’ larva Eggs fall into intestine and thus are excreted with faeces As long as egg reaches, damp warm soil surface, it starts to hatch Goes through an series of developmental stages to form a filariform larva Process takes 7-10 days Filariform larva wait for suitable host to arrive Can survive for several months, but often die after a few weeks from dessication and exposure to sunlight

Answer 16

Thin outer shell, larval worm

Answer 17

Easily preventable disease Wear shoes! Can treat with anthelminthic drugs (mebendazole, albendazole) , iron tablets etc Not everybody has same ‘worm burden’, but if re-infected, tend to acquire a similar number of adult worms Plenty of studies have shown this, but not really explained why!

Answer 18

``` Concentration method ( e.g. formol-ether) Wet preparation- no stain needed ```

Parasitology Flashcards

(42 cards)