Biology Reference
In-Depth Information
In the absence of a practicable means of diagnosing G6PD deficiency,
many regions opt not to use primaquine in the treatment of symptom-
atic
P. vivax
infections. In these situations, use of very slowly eliminated
blood schizontocidal regimens such as dihydroartemisinin plus piperaquine,
artesunate plus mefloquine and chloroquine (where parasites remain fully
susceptible) has the potential to suppress the first relapse of tropical strains
of
P. vivax
. Where
P. vivax
transmission is intense, this should reduce total
life-time parasite carriage. Large, multi-centre randomised trials in which
patients are assigned to repeated doses of the same drug are required to
prove this speculative assertion.
Given the high rate of
P. vivax
relapse following falciparum malaria in
co-endemic areas, there is an argument for using hypnozoitocidal doses
of primaquine in those with falciparum malaria in co-endemic regions.
This proposition raises important ethical dilemmas related to a dubious
risk:benefit ratio. If G6PD testing becomes widely available allowing safe
prescription of primaquine, these dilemmas may become redundant.
Asymptomatic
P. vivax
infections are likely to be responsible for a sub-
stantial proportion of all
P. vivax
transmission, especially in moderately and
highly endemic areas. Two means of treating asymptomatic individuals
include mass screening and treatment and mass presumptive drug admin-
istration. Since
P. vivax
infections are efficiently transmitted at sub-patent
gametocyte densities and the presence or absence of hypnozoites cannot be
established in those without blood-stage infection, MDA is likely to have
the greater impact of these two approaches. Eradication of hypnozoites will
be critical to the effectiveness of these strategies. If G6PD status can be
established, a slowly eliminated hypnozoitocidal agent such as tafenoquine
may prove to be particularly useful for single-visit campaigns.
P. vivax
has side-stepped current malaria control efforts and is becoming
a proportionately more common cause of malaria globally. Development of
a safe and effective means of eradicating
P. vivax
hypnozoites will be critical
to reversing this trend.
REFERENCES
Aguas, R., Ferreira, M.U., Gomes, M.G., 2012. Modeling the effects of relapse in the trans-
mission dynamics of malaria parasites. J. Parasitol. Res. 2012 921715.
Alexandre, M.A., et al., 2010. Severe
Plasmodium vivax
malaria, Brazilian Amazon. Emerg.
Infect. Dis. 16 (10), 1611-1614.
Alving, A.S., et al., 1953. Korean vivax malaria. II. Curative treatment with pamaquine and
primaquine. Am. J. Trop. Med. Hyg. 2 (6), 970-976.
Alving, A.S., et al., 1955. Potentiation of the curative action of primaquine in vivax malaria
by quinine and chloroquine. J. Lab. Clin. Med. 46 (2), 301-306.
