Insights into Plasmodium vivax from spatial maps of human gene polymorphisms: Duffy blood group and G6PD deficiency.

Rosalind Howes (April 9, 2014)

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Slides

0:03 Insights into Plasmodium vivax from spa/al maps of human gene polymorphisms: Duffy blood group and G6PD deficiency
2:25 Malaria Atlas Project
3:23 MAP-Inherited Blood Disorders
3:39 Talk overview
4:30 Plasmodium vivax
7:47 Mapping the Duffy blood group
8:15 The datapoints
12:21 The model
12:59 Geostatistics: the random field
14:24 Geostatistics: the random field (2)
14:49 Geostatistics: the random field (3)
16:04 Geostatistics: making maps
16:44 Duffy allele frequencies
17:01 Dominant Duffy alleles (composite)
17:55 Duffy negative phenotype prevalence
18:06 P. vivax endemicity mapping
19:26 G6PD deficiency & Primaquine
21:09 Flow chart 1
21:25 G6PD: an X-linked gene
22:32 Phenotype-based diagnostics: the evidence-base
24:17 Prevalence of G6PDd: allele freq.
24:26 Prediction uncertainty: IQR
25:11 Flow chart (2)
25:25 Population affected
26:36 G6PDd: not a single disorder
27:34 G6PDd variants
28:49 G6PDd variants (2)
29:27 Primaquine treatment
30:42 G6PDd epidemiology
31:37 Hay et al. PLoS Med (2013)
33:25 Acknowledgements

Abstract

Over a third of the world€™s population lives at risk of potentially life-threatening Plasmodium vivax malaria infections. Unique aspects of this parasite€™s biology and interactions with its human host make it harder to control and eliminate than the better studied Plasmodium falciparum parasite. The spatial epidemiology of two human genetic systems associated with these traits has been investigated in a multi-scale, model-based framework to generate estimates of populations of risk of P. vivax infection, and assessments of associated therapeutic risks.


First, the two key SNPs determining expression of the Duffy blood group were modelled to map the prevalence of Duffy phenotypes globally. The Duffy antigen is the only known erythrocyte receptor for P. vivax infection, and was used as a proxy indicator of population susceptibility to infection. The maps are discussed in light of reports of apparent Duffy-independent transmission.


Second, the global epidemiology of G6PD enzyme deficiency €“ both its phenotypic prevalence and genetic heterogeneity €“ is mapped. A geostatistical framework structured around the gene€™s X-linked inheritance generated global estimates of G6PD deficiency prevalence, and estimates of affected population numbers. Poorly quantified risks from this spatially heterogeneous enzyme deficiency currently hinder widespread use of primaquine, a drug necessary for progress towards malaria elimination, particularly against the relapsing P. vivax life-stages.


These examples illustrate the positive contribution that integrating spatial epidemiological human genetic data can make in supporting the evidence-base for strategic planning for control of an infectious disease, thereby attempting to bridge the gap between basic biological research and the health sciences.