malaria Flashcards
definition of malaria
infection with protozoan Plasmodium
(plasmodium falciparum, plasmodium vivax, plasmodium ovale, and plasmodium malariae)
most serious is plasmodium falciparum - which is potentially fatal
epidemiology of malaria
endemic in tropics
affects 250million people world wide yearly
there are about 2000 cases and 10 deaths/yr in UK
subsaharan Africa has 88% of cases and 90% deaths
falciparum is most prevalent parasite in Africa, and responsible for most deaths world wide
p vivax most dominant parasite outside sub-saharan Africa
incidence and deaths have redued
aetiology of malaria
The Plasmodium spp, are transmitted by the bite of femal anopheles mosquito
the protazoa infect the red blood cells and grow intracellularly
- injection of sporozoites into the bloodstream by the bite of the female - anopheles mosquito
- invasion and replication in the hepatocytes (exoerythrocytic schizogeny) P. vivax and P. ovale may develop into dormant hypnozoites and cause relapse within months or years
- parasites may reinvade the blood (at this point called merozoites). Inside the RBC parasites develop from ring forms (trophozoites) to multinucleated schizonts (erythrocytic schizogeny)
- RBC rupture and release merozoites (cause symptoms), which may reinfect new RBC - some differentiate into male and female gametocytes
- gametocytes are taken up by anopheles mosquitoes, develop into sporozoites in their gut and migrate to salivary gland of mosquito to be transmitted in their bite
which populations have innate immunity to malaria
sickle cell trait
G6PD deficiency
pyruvate kinase deficiency
thalassaemias
sx of malaria
high degree of clinical suspicion in feverish traveller (incubation up to 1yr, but usually 1-2wks)
cyclical symptoms - high fever, flulike symptoms, severe sweating and shivering cold/rigors
headache, malaise, myalgia, diarrhoea, cough
peak temp may coincide with rupture of the intra-erythrocytic schizonts:
- every 48hr for P. falciparum (malignant tertian)
- every 72hr for P. malariae (benign quartan)
- every 48hr for P. vivax and P. ovale (benign tertian)
sx of cerebral malaria
headache
disorientation
coma
signs of malaria
pyrexia/rigors
anaemia
hepatosplenomegaly
if dx is delayed/severe disease - jaundice, confusion, seizures
Ix for malaria
- Thick/thin blood film (using Field’s or Giemsa’s stain)
- measure for daily detection and quantitive count of level of intracellular ring forms has to be -ve for 3days to exclude
- if -ve repeat at 12-24hr and after another 24hr
- >2% parasitized red cells in P. falciparum is chance of severe, >10% is severe
- blood
- FBC (Hb, platelets) UE, LFT, ABG (pH)
- rapid detection test
- detection of parasite ag
- used for initial scrreen if microscopy not available
- urinalysis
- test for blood or protein
- urine output
- quantitive buffy coat (QBC) test
- acridine orange stains parasite nucleus
- lower sensitivity than blood films
- immunochromatographic test
- detects histidine rich protein 2 found only in P falciparum
- lower sensitivity than blood films
transmission of malaria aside from a mosquito bite
rare
vertical
transfusion
organ transplantation
needle sharing
p falciparum
av incubation 6days
no persistent liver phase
Africa, India, South East Asia, Indonesia, Oceania, Central America, Middle East
p vivax
av incubation - 14days
persistent liver phase
South Asia, South and Central America, Africa, Middle East
p malariae
av incubation - 30 days
no persistant liver phase
Africa, South and Central America, South East Asia
p ovale
av incubation 11-16days
persistent live rphase
africa
P knowlesi
incubation phase - 9-12days
no persistent liver phase
South East Asia
mx of malaria
P falciparum mild:
* chloroquine / hydroxychloroquine
severe disease (p falciparum) = artesunate parentally then switch to oral - artemether/lumefantrine + primaquine
P ovale / vivax - chloroquine / hydroxychloroquine + primaquine
p malariae / knowlesi - chloroquine / hydroxychloroquine
