Biology Reference
In-Depth Information
high occupational risk of malaria prevented 93% and 93% of vivax malaria
episodes, respectively (
Lwin et al., 2012
). Both regimens appeared to pro-
tect against
P. vivax
gametocytaemia though tests of statistical significance
specifically for this species were not given (
Lwin et al., 2012
). Weekly doses
of chloroquine during pregnancy in a Karen population on the Thai-Myan-
mar border had 100% protective efficacy against
P. vivax
malaria, as detected
by light microscopy (
Villegas et al., 2007
). Protection against clinical vivax
malaria episodes or gametocytaemia detected by light microscopy does not
necessarily equate to a reduction in transmission of the parasite. Evidence
from large scale, cluster-randomised studies with long-term follow-up will
be required before the potential of intermittent preventive treatment in
infancy, childhood or pregnancy to reduce transmission of
P. vivax
can be
established firmly.
Finally, MDA may increase drug pressure on the local parasite popula-
tion and, therefore, promote the emergence of drug-resistant strains. For this
reason, it has been suggested that first-line blood-schizontocidal therapies
should be avoided in MDA programmes (
Bousema and Drakeley, 2011
).
Acquired hypnozoite resistance to primaquine has not yet been proved but
if it occurred would be particularly disastrous since there is no licensed
alternative.
5. CONCLUSIONS
Anti-malarial drugs are an important means of reducing transmission
of
P. vivax
infections. In the treatment of symptomatic disease, the primary
consideration is prevention of recurrences due to recrudescence and relapses.
Short course, potent and relatively slowly eliminated blood schizontocidal
regimens administered concurrently with a total dose of 7 mg/kg primaquine
(except in areas where there is solid evidence that a total dose of 3.5 mg/kg
primaquine is effective) will have the greatest potential to reduce transmis-
sibility of individual
P. vivax
infections. Given the spread of
P. vivax
strains that
are resistant to chloroquine, the artemisinin combination therapies dihydro-
artemisinin + piperaquine and artesunate + mefloquine are the most assured
means of preventing recrudescence. Preliminary evidence suggests that,
like chloroquine, these combinations potentiate the hypnozoitocidal effect
of primaquine, but further supportive evidence is required to solidify this
claim. Two factors limit the potential effectiveness of primaquine in endemic
regions: poor adherence to the 14-day-treatment regimen and reluctance to
prescribe this drug because of the risk of primaquine-induced haemolysis in
