Parasite Flashcards
What is the difference between parasitic symbiosis and commensal?
Parasitic symbiosis – one member benefits, other is harmed
Commensals - parasites that derive benefit from host without causing harm
What are the types of parasites?
protozoa
helminths
arthropods
What are the properties of protozoa?
most parasitic protozoa are usually <50μm
unicellular eukaryotes
nucleus has a membrane
protozoa can twist and bend
What are the structural features of protozoa and their function?
macronucleus and micronucleus
cilia
- locomotory structure
- hair-like structure that cover the outside of the microbe and beat in a regular, continuous pattern = movement
pellicle
- covers the outer surface
- rigid enough to support and maintain shape but allows bending and twisting when moving
gullet
- food is pushed in to form the food vacuoles
food vacuole
- storage of food
- acts as intracellular stomach, digest food by fusing with lysosomes
contractile vacuole
- helps osmoregulation
- pumps out excess water by fusing with the membrane
anal pore
- waste is ejected
How do protozoa get their nutrition?
protozoa are holozoic
- require organic material = consumption of liquid or solid food
can engulf particulate food from the gullet
many protozoa have a permanent mouth = cytostome
pinocytosis
- process of drawing in fluid via the vesicles
What are examples of protozoa and their properties?
amoeba - move using pseudopods and divide by binary fission
ciliates - possess cilia, two different types of nucleus and transverse fission of organism when it divides
flagellates - move using flagella and divide by binary fission
sporozoa - complex life cycle involving alternating cycles of asexual and sexual development
entamoeba histolytica
- anaerobic parasitic protozoal commensal
- invasion of the intestinal lining causes amoebic dysentery – called Amoebiasis
transmitted by faecal-oral route
infect GIT - can pass into blood and infect liver
What is malaria? What is it caused by?
malaria is a disease caused by parasite caused by - plasmodium falciparum - plasmodium vivax - plasmodium malariae - plasmodium Ovale
Life cycle
- two life cycles in human
- as an indirect life cycle
What is the life cycle of malaria in humans?
malarial parasites are transmitted by infected female (only female as they have eggs) anopheline mosquitos
mosquitos injects sporozoites in their saliva into the blood of humans
1st cycle - asexual and sexual cycle
spororzoites circulate the blood then settle in the parenchymal cells of the liver and multiply
= pre-erythrocytic schizogony = asymptomatic stage
spororzoites can either
- infect parenchymal cells in the liver where they remain dormant = hypnozoites
- multiply to produce merozoites
after 12 days, the parenchymal cells rupture and release the merozoites into the blood to infect red blood cells
in the RBCs the merozoites mature into trophozoites the transform to form daughter merozoites
some merozoites transform into male and female gametocytes
2nd cycle RBCs rupture and release - male and female gametocytes - toxins = show symptoms of malaria - new merozoites to infect other RBCs
gametocytes and merozoites circulate the blood and are eventually picked up by female mosquitos as they bitt he human
What is the life cycle of malaria in mosquitoes?
gametocytes are picked up by female mosquitos as they bite the human
in the mosquito the female gametocytes transform into ookinete
the ookinete is fertilised and forms an oocyst which produces sporozoites
spororzoites move to the salivary gland and are ready to be injected into the next human
What are trophozoites and oocysts?
trophozoite - the active feeding and multiplying stage
oocysts - the stages resulting from sexual reproduction, this stage characterised with a protective membrane or thickened wall.
What is malaria treatment?
treatment is effective with various quinine derivatives
- quinine sulphate, chloroquine, mefloquinine, primaquine
drugs effective against the exoerythrocytic form - before it enters the parenchymal cells in the liver
- primaquine
- stops the parenchymal cells from rupturing
drugs effective against the erythrocytic form - within th RBC
- artemisinin
- chloroquine
- kill the trophozoites and merozoites within the RBC
drugs effective against the gametocytic form
- primaquine
- kill the gametocytes
What are the types of helminths and their properties?
they are worm-like parasites
- flukes = trematodes
- tapeworms = cestodes
- roundworms = nematodes
they are invertebrates
helminths develop though egg, larval and adult stages
What are the clinically important cestodes (tapeworms) ? What is their structure?
clinically important cestodes are
- tenia solium
- tenia saginata
- echinococcus granulosus
generally flattened, elongated and consists of segments, proglottids
vary in length, 2mm –10m
anatomically divided into
- scolex = head
- neck = region of segment proliferation
- strobila = chain of proglottids (segments of the tapeworm)
What are the characteristic of cestodes (tapeworms)? What is their treatment?
- characteristic feature is absence of alimentary canal
- substances enter the tapeworm across the tegument
- cestodes are hermaphrodotic = each proglottid possess male and female reproductive systems
- eggs are deposited in different methods according to the type of tapeworm
treatment
- praziquantel is used to treat many tenia infections
- expulsion of the scolex (head) is a must
- must have good hygiene - especially regarding animals and children
How do arthropods infect humans with disease? What are examples?
- act as vectors
- acts as parasites
- illicit allergies
examples
- lice
- fleas
- mites
- ticks
