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Figure 1.10, cont'd
is again referred to a detailed review of the effect of the lacking Duffy anti-
gen on resistance to P. vivax provided in this thematic issue of Advances in
Parasitology (Chapter 2, Volume 81). The Duffy antigen refers to a receptor
expressed on the surface of red blood cells, which P. vivax has been shown to
be dependent upon for erythrocytic invasion ( Miller et al., 1976 ; Barnwell
et al., 1989 ; Wertheimer and Barnwell, 1989 ). Duffy-negative individuals,
who lack the antigen, are therefore largely refractory to P. vivax infection and
high frequencies of the phenotype are presumed to suppress P. vivax ende-
micity in areas that would otherwise be well suited for transmission. A con-
tinuous map of the Duffy-negative phenotype, described in detail elsewhere
( Howes et al., 2011 ) and briefly here, was used as the exclusion surface.
To model the global distribution of the Duffy-negative phenotype, a data-
base of Duffy blood group surveys was assembled. Surveys of Duffy-variant
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