Biology Reference
In-Depth Information
et al., 1999
;
Baird and Rieckmann, 2003
;
Rowland and Durrani, 1999
).
In another model, Aguas et al. found that an MDA campaign including a
blood schizontocidal medication in combination with a wholly effective
hypnozoitocidal course of primaquine would reduce the incidence of
P.
vivax
as rapidly as
P. falciparum
(
Aguas et al., 2012
)
.
However, the authors also
showed that the re-emergence of
P. vivax
would be much more rapid than
P. falciparum
following reintroduction of foreign strains from nearby regions
(
Aguas et al., 2012
).
Eradicating hypnozoites is clearly critical to the effectiveness of MDA
efforts. If only a single round of drug treatment is possible, a full hypnozo-
itocidal course of primaquine should theoretically be provided. However,
given the dangers of daily dosing in G6PD-deficient individuals or pregnant
mothers with G6PD deficient foetuses, the G6PD and pregnancy status of
each individual should ideally be established before providing primaquine.
Given that most individuals in the population will be healthy, adherence to
a 2-week course is likely to be very poor, and thus threaten the utility of
this drug. If individual G6PD and pregnancy status was known, tafenoquine
might be a very useful alternative hypnozoitocidal drug due to its long
half-life and resultantly short treatment regimen. Short-course, high-dose
primaquine regimens have been effective in clinical studies (
Krudsood
et al., 2008
;
Clyde and McCarthy, 1977
) and may also be useful for single-
visit MDA campaigns.
Young children are at greater risk of high-parasitaemia
P. vivax
infections
than adults and are more likely to have patent
P. vivax
relapses (
Douglas
et al., 2011
;
Phimpraphi et al., 2008
). Ostensibly, this would suggest that
targeting young children may maximise the cost-effectiveness of MDA
campaigns for reducing
P. vivax
transmission. However, children are also
the most likely to experience symptomatic infections and are, therefore,
more likely to present passively for treatment than adults (
Douglas et al.,
2011
). The prevalence of hypnozoites in this age group will be lower than
in adults. Intermittent preventive treatment in infancy (IPTi) and child-
hood (IPTc) are two age-limited forms of repeated MDA that have been
employed for reducing morbidity associated with malaria, particularly in
regions that are highly endemic for
P. falciparum.
Senn et al. recently showed
that intermittent preventive treatment of infants with SP + AQ or AS + SP
reduced the incidence of clinical vivax malaria episodes in Papua New
Guinea by 23% and 4%, respectively (less than the corresponding reductions
for
P. falciparum
) (
Senn et al., 2012
). On the Thai-Myanmar border, monthly
or alternate monthly courses of DHA + PIP in healthy adult males at
