13. Parasitology & Malaria Flashcards
define a parasitic relationship
one in which the organism lives off another organism (the host) harming it and possibly causing death
what are protozoa
single celled organism
what are helminths
worms, multicellular, often produce eggs
give an example of a protozoan parasite
plasmodium
leishmania
giardia
give an example of a helminth
schistosomes
roundworm
how can we directly diagnose a parasite
visualising the parasite or a compound of the parasite (its DNA)
What is an indirect way of diagnosing a parasite
using clinical diagnosis, biochemical and serological tests
what are useful samples that can be taken to diagnose parasites
blood and stool
what does sensitivity mean
the proportion of true positives identified
what does specificity mean
the proportion of true negatives identified
how can we figure out sensitivity
true positives / false negatives + true positives
how can we figure out specificity
true negatives / false positives + true negatives
what does a good test have in terms of sensitivity and specificity
high sensitivity and specificity (>90%) - although there is often a trade off
in a life threatening situation, what is more important:
sensitivity or specificity
sensitivity - more important to known who truly has it
if treatment is expensive with serious side effects, what Is more important:
sensitivity or specificity
specificity = more important to know that only those who truly have it are being treated
what is the main species that causes human malaria
plasmodium falciparum
how does malaria transmission occur
the bite of female anopheles mosquito
are there any known reservoirs of plasmodium?
no significant reservoirs, except P. knowlsei in macaque monkeys
how many malaria deaths per year
400,000
where are most malaria cases
in africa
what % of cases is P. falciparum responsible for
50% of cases
describe the erythrocytic cycle of P. falciparum
merozoites invade RBCs to evade the host’s immune system
here they undergo an asexual reproduction cycle which produces trophozoites
why is the erythrocytic cycle important in diagnosis
examining blood films to detect the stages of infection are key in diagnosis
what is the second most prevalent plasmodium
P. vivax
