Biology Reference
In-Depth Information
individuals harbouring hypnozoites who do not have blood-stage infection
are treated is to distribute anti-malarial drugs to everybody (MDA).
For the reasons outlined previously, effective hypnozoitocidal therapy
is likely to be much more important in mass screening and treatment
campaigns than blood schizontocidal treatment (
Aguas et al., 2012
). Since
only a small proportion of people treated in MDA campaigns will have
blood-stage infection, the relative importance of hypnozoitocidal therapy
in this strategy will be even greater. Between the third and the fifth of
November 1981, 70% of the population of Nicaragua (∼1.9 million people)
received a 3-day course of chloroquine (1500 mg total dose) and primaquine
(45 mg total dose) (see Chapter 6 for descriptions of several historical MDA
campaigns). This intervention was associated with a subsequent reduction
in the incidence of both
P. falciparum
and
P. vivax.
The effect on
P. falci-
parum
lasted for approximately 9 months, whereas for
P. vivax
, it lasted just
4 months (
Garfield and Vermund, 1983
). The authors of the analysis sug-
gested that the limited effectiveness against
P. vivax
was likely to relate to the
inadequate dose of primaquine administered (
Garfield andVermund, 1983
).
In the Ghab region in Syria, a weekly dose of chloroquine and pyri-
methamine administered in conjunction with indoor residual spraying of
dichlorodiphenyltrichloroethane (DDT) between August and October
1968 resulted in a rapid and marked reduction in the incidence of vivax
malaria from 470 cases in 1968 to 114 cases in 1969 (
Onori, 1972
). Based
on the results of concurrent entomological surveillance, the authors con-
cluded that all 114 of the cases in 1969 (92 of which were in individuals
who had received presumptive drug treatment) were relapses (
Onori, 1972
).
Without continued aggressive vector control, these relapses are likely to
have led to a rebound in vivax malaria incidence, however further spraying
of dieldrin in May and August helped to ensure a complete absence of cases
in 1970.
On the pacific island of Aneityum in the Vanuatu archipelago (popula-
tion 718 people) weekly MDA of chloroquine, sulfadoxine + pyrimeth-
amine and primaquine (45 mg) for 9 weeks in conjunction with distribution
of insecticide-treated bednets and introduction of larvivorous fish resulted
in complete suppression of malaria transmission due to both
P. falciparum
and
P. vivax
(
Kaneko et al., 2000
;
Kaneko, 2010
). Periodic malariomet-
ric surveillance over the following 9 years showed that, aside from two
imported cases of malaria (one due to
P. vivax
and the other due to mixed
P. vivax/P. falciparum
infection), malaria was eliminated from the island. The
single 45 mg dose of primaquine was given during seven of the nine weekly
