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In-Depth Information
of the potential DVS in this region (
Table 1.2
). Further research identifying
which anopheline species are the most efficient vectors of this parasite will
be beneficial to the Africa+ region as goals of control and elimination of
P. falciparum
are realised and the focus moves to address
P. vivax
.
Africa+ summary
. Estimates of the PAR of
P. vivax
in Africa, which is
climatically well suited for malaria transmission, were very low, with the
exception of countries around the Horn of Africa. This was because of the
assumption that Duffy negative individuals, found in high frequencies on
the continent (
Howes et al., 2011
), are refractory to
P. vivax
infection. This
supposition was incorporated into the model, despite observations of
P. vivax
malaria infections in Duffy-negative individuals in Madagascar (
Menard
et al., 2010
) and on the mainland of the continent (
Ryan et al., 2006
;
Mendes
et al., 2011
;
Wurtz et al., 2011
). While this information contradicts our work-
ing assumption of complete protection, there is insufficient evidence to
determine if these are more than just rare occurrences on the continent that
would have a significant effect on the epidemiology of
P. vivax
in Africa.
Prevalence estimates for Africa are characterised by low predicted values
and high levels of uncertainty (
Fig. 1.4
D). The PR data from Africa that
served as the input data for the endemicity predictions were sparse, with
the exception of a few regions (
Fig. 1.3
D1). This is largely because
P. vivax
is not the main priority for Africa. There were 753 million people at risk of
stable
P. falciparum
in Africa in 2010 (
Gething et al., 2011a
), compared to the
38 million at stable risk
P. vivax
. However, 30% (228 million) of the 753 mil-
lion were living in regions of low stable transmission (
Pf
PR
2-10
≤ 5%); the
prevalence of
P. falciparum
in these areas falls to a point where elimina-
tion is viable, the situation of
P. vivax
will increase relatively, a consequence
of its tendency to be the last parasite standing during elimination efforts
(
Garnham, 1951
;
Yekutiel, 1960
;
Pampana, 1969
;
Wernsdorfer et al., 2009
;
Tatem et al., 2010
). This reinforces the need for increased vector surveillance
and incrimination of species specifically for
P. vivax
. The endemicity map
(
Fig. 1.3
D2) presented indicates that while
P. vivax
is present at very low lev-
els in Africa, it is circulating. Consideration for how those prevalence esti-
mates may be affected by decreasing
P. falciparum
levels must be considered.
4.5. Areas Where Lack of Geographical Data is Acute
Asia
. Although there was thorough coverage of annual clinical incidence
data and a large number of prevalence data records, given the large area of
Pv
MECs in Central Asia (20.5 million km
2
), there were still large regions
with a dearth of data (
Fig. 1.3
A1). These regions are highlighted by the
