Children with Plasmodium vivax infection previously observed in Namibia, were Duffy negative and carried a c.136G > A mutation

Background In a previous study, using a molecular approach, we reported the presence of P. vivax in Namibia. Here, we have extended our investigation to the Duffy antigen genetic profile of individuals of the same cohort with and without Plasmodium infections. Methods Participants with P. vivax (n = 3), P. falciparum (n = 23) mono-infections and co-infections of P. vivax/P. falciparum (n = 4), and P. falciparum/P. ovale (n = 3) were selected from seven regions. Participants with similar age but without any Plasmodium infections (n = 47) were also selected from all the regions. Duffy allelic profile was examined using standard PCR followed by sequencing of amplified products. Sequenced samples were also examined for the presence or absence of G125A mutation in codon 42, exon 2. Results All individuals tested carried the − 67 T > C mutation. However, while all P. vivax infected participants carried the c.G125A mutation, 7/28 P. falciparum infected participants and 9/41 of uninfected participants did not have the c.G125A mutation. The exon 2 region surrounding codon 42, had a c.136G > A mutation that was present in all P. vivax infections. The odds ratio for lack of this mutation with P. vivax infections was (OR 0.015, 95% CI 0.001–0.176; p = 0.001). Conclusion We conclude that P. vivax infections previously reported in Namibia, occurred in Duffy negative participants, carrying the G125A mutation in codon 42. The role of the additional mutation c.136 G > A in exon 2 in P. vivax infections, will require further investigations.

Plasmodium vivax and Plasmodium ovale in the Malaria Elimination Agenda in Africa

In recent times, several countries in sub-Saharan Africa have reported cases of Plasmodium vivax (Pv) with a considerable number being Duffy negative. Current efforts at malaria elimination are focused solely on Plasmodium falciparum (Pf) excluding non-falciparum malaria. Pv and Plasmodium ovale (Po) have hypnozoite forms that can serve as reservoirs of infection and sustain transmission. The burden of these parasites in Africa seems to be more than acknowledged, playing roles in migrant and autochthonous infections. Considering that elimination and eradication is a current aim for WHO and Roll Back Malaria (RBM), the inclusion of Pv and Po in the elimination agenda cannot be over-emphasized. The biology of Pv and Po are such that the same elimination strategies as are used for Pf cannot be applied so, going forward, new approaches will be required to attain elimination and eradication targets.

High frequency of the Duffy-negative genotype and absence of Plasmodium vivax infections in Ghana

Background Recent studies from different malaria-endemic regions including western Africa have now shown that Plasmodium vivax can infect red blood cells (RBCs) and cause clinical disease in Duffy-negative people, though the Duffy-negative phenotype was thought to confer complete refractoriness against blood invasion with P. vivax. The actual prevalence of P. vivax in local populations in Ghana is unknown and little information is available about the distribution of Duffy genotypes. The aim of this study was to assess the prevalence of P. vivax in both asymptomatic and symptomatic outpatients and the distribution of Duffy genotypes in Ghana. Methods DNA was extracted from dried blood spots (DBS) collected from 952 subjects (845 malaria patients and 107 asymptomatic persons) from nine locations in Ghana. Plasmodium species identification was carried out by nested polymerase chain reaction (PCR) amplification of the small-subunit (SSU) rRNA genes. For P. vivax detection, a second PCR of the central region of the Pvcsp gene was carried out. Duffy blood group genotyping was performed by allele-specific PCR to detect the presence of the FYES allele. Results No cases of P. vivax were detected in any of the samples by both PCR methods used. Majority of infections (542, 94.8%) in the malaria patient samples were due to P. falciparum with only 1 infection (0.0017%) due to Plasmodium malariae, and 2 infections (0.0034%) due to Plasmodium ovale. No case of mixed infection was identified. Of the samples tested for the FYES allele from all the sites, 90.5% (862/952) had the FYES allele. All positive samples were genotyped as FY*B-33/FY*B-33 (Duffy-negative homozygous) and therefore classified as Fy(a−b−). Conclusions No cases of P. vivax were detected by both PCRs and majority of the subjects tested carried the FYES allele. The lack of P. vivax infections observed can be attributed to the high frequency of the FYES allele that silences erythroid expression of the Duffy. These results provide insights on the host susceptibility for P. vivax infections that had not been investigated in Ghana before.

Plasmodium vivax from Duffy-Negative and Duffy-Positive Individuals Shares Similar Gene Pool in East Africa

Plasmodium vivax malaria was thought to be rare in Africa, but an increasing number of P. vivax cases reported across Africa and in Duffy-negative individuals challenges this conventional dogma. The genetic characteristics of P. vivax in Duffy-negative infections, the transmission of P. vivax in East Africa, and the impact of environments on transmission remain largely unknown. This study examined genetic and transmission features of P. vivax from 107 Duffy-negative and 305 Duffy-positive individuals in Ethiopia and Sudan. No clear genetic differentiation was found in P. vivax between the two Duffy groups, indicating between-host transmission. P. vivax from Ethiopia and Sudan showed similar genetic clusters, except samples from Khartoum, possibly due to distance and road density that inhibited parasite gene flow. This study is the first to show that P. vivax can transmit to and from Duffy-negative individuals and provides critical insights into the spread of P. vivax in sub-Saharan Africa.

Duffy Blood System and G6PD Genetic Variants In P. Vivax Malaria Patients From Manaus, Amazonas, Brazil

Over a third of the world’s population lives at risk of potentially severe Plasmodium vivax induced malaria. The unique aspect of the parasite’s biology and interactions with the human host make it harder to control and eliminate the disease. Glucose-6-phosphate dehydrogenase (G6PD) deficiency and Duffy-negative blood groups are two red blood cell variations that confer protection against malaria. Molecular genotyping of G6PD and Duffy was performed in 225 patients with severe and non-severe malaria. Of the 225 patients, 29 (12.94%) and 43 (19.19%) were carriers of the G6PD c.202G>A and c.376A>G, respectively. For the Duffy genotype (c.-67T>C in the GATA promoter region), 70 (31.11%) were phenotyped as Fy(a+b-), 98 (43.55%) Fy(a+b+), 56 (24.9%) Fy(a-b+) and 1 (0.44%) Fy(a-b-). The FY*01/FY*02 genotype was prevalent in both non-severe and severe malaria. However, the frequency increased when SNP c.376A>G was also present. In women, the FY*01/FY*02 allele occurred concomitantly with c.376A>G more frequently in non-severe malaria, while in men, this combination is revealed predominantly in severe malaria. G202A and A376G G6PD variants were higher in severe malaria, with c.202G>A (RR= 4.76 – p=.009) and c.376A>G (RR: 6.47 – p<0.001) strongly associated with the trials malaria (p<0.001). Duffy phenotype Fy(a-b+) (p=0.003) and genotype FY*02/ FY*02 (p=0.007) presented the highest values parasitemia density of the vivax malaria. Research on G6PD and Duffy antigen deficiencies has been valuable, particularly when focused on densely populated areas. Altogether, c.202G>A and c.376A>G SNPs seem to be risk factors for the development of severe vivax malaria. Molecular diagnosis before treatment may be necessary in the Amazonian population and uncomplicated malaria showed a greater frequency of variation for GATA and G6PD variants than severe malaria.

Duffy Blood System and G6PD Genetic Variants In P. Vivax Malaria Patients From Manaus, Amazonas, Brazil

Over a third of the world’s population lives at risk of potentially severe Plasmodium vivax induced malaria. The unique aspect of the parasite’s biology and interactions with the human host make it harder to control and eliminate the disease. Glucose-6-phosphate dehydrogenase (G6PD) deficiency and Duffy-negative blood groups are two red blood cell variations that confer protection against malaria. Molecular genotyping of G6PD and Duffy was performed in 225 patients with severe and non-severe malaria. Of the 225 patients, 29 (12.94%) and 43 (19.19%) were carriers of the G6PD c.202G>A and c.376A>G, respectively. For the Duffy genotype (c.-67T>C in the GATA promoter region), 70 (31.11%) were phenotyped as Fy(a+b-), 98 (43.55%) Fy(a+b+), 56 (24.9%) Fy(a-b+) and 1 (0.44%) Fy(a-b-). The FY*01/FY*02 genotype was prevalent in both non-severe and severe malaria. However, the frequency increased when SNP c.376A>G was also present. In women, the FY*01/FY*02 allele occurred concomitantly with c.376A>G more frequently in non-severe malaria, while in men, this combination is revealed predominantly in severe malaria. G202A and A376G G6PD variants were higher in severe malaria, with c.202G>A (RR= 4.76 – p=.009) and c.376A>G (RR: 6.47 – p<0.001) strongly associated with the trials malaria (p<0.001). Duffy phenotype Fy(a-b+) (p=0.003) and genotype FY*02/ FY*02 (p=0.007) presented the highest values parasitemia density of the vivax malaria. Research on G6PD and Duffy antigen deficiencies has been valuable, particularly when focused on densely populated areas. Altogether, c.202G>A and c.376A>G SNPs seem to be risk factors for the development of severe vivax malaria. Molecular diagnosis before treatment may be necessary in the Amazonian population and uncomplicated malaria showed a greater frequency of variation for GATA and G6PD variants than severe malaria.

Alternative Invasion Mechanisms and Host Immune Response to Plasmodium vivax Malaria: Trends and Future Directions

Plasmodium vivax malaria is a neglected tropical disease, despite being more geographically widespread than any other form of malaria. The documentation of P. vivax infections in different parts of Africa where Duffy-negative individuals are predominant suggested that there are alternative pathways for P. vivax to invade human erythrocytes. Duffy-negative individuals may be just as fit as Duffy-positive individuals and are no longer resistant to P.vivax malaria. In this review, we describe the complexity of P. vivax malaria, characterize pathogenesis and candidate invasion genes of P. vivax, and host immune responses to P. vivax infections. We provide a comprehensive review on parasite ligands in several Plasmodium species that further justify candidate genes in P. vivax. We also summarize previous genomic and transcriptomic studies related to the identification of ligand and receptor proteins in P. vivax erythrocyte invasion. Finally, we identify topics that remain unclear and propose future studies that will greatly contribute to our knowledge of P. vivax.

Contrasting Epidemiology and Genetic Variation of Plasmodium vivax Infecting Duffy Negatives across Africa

Recent studies indicated that Plasmodium vivax can infect Duffy-negative individuals, but the varied diagnostic and methodological approaches have limited our ability to characterize P. vivax across Africa. Here, we utilized a standardized approach to compare epidemiological and genetic attributes of P. vivax from Botswana, Ethiopia, and Sudan, where Duffy-positive and Duffy-negative individuals coexist. Among 1,215 febrile patients, the proportions of Duffy negativity range from 20-36% in East Africa to 84% in Southern Africa. Considerable differences were observed in P. vivax prevalence among Duffy-negative populations ranging from averaged 9.2% in Sudan to 86% in Botswana. P. vivax parasite density in Duffy-negative infections is significantly lower than in Duffy-positive infections. Phylogenetic analyses of 229 PvDBP sequences indicated that Duffy-negative P. vivax were not monophyletic but occurred in multiple well-supported clades, suggesting independent origins. Duffy-negative Africans are clearly not resistant to P. vivax and the public health significance should no longer be neglected.

Alternative Invasion Mechanisms and Host Immune Response to Plasmodium vivax Malaria: Trends and Future Directions

Plasmodium vivax malaria is a neglected tropical disease, despite being more geographically widespread than any other form of malaria. The documentation of P. vivax infections in different parts of Africa where Duffy-negative individuals are predominant suggested that there are alternative pathways for P. vivax to invade human erythrocytes. Duffy-negative individuals may be just as fit as Duffy-positive individuals and are no longer resistant to P. vivax malaria. In this review, we describe the complexity of P. vivax malaria, characterize pathogenesis and candidate invasion genes of P. vivax, and host immune responses to P. vivax infections. We provide a comprehensive review on parasite ligands in several Plasmodium species that further justify candidate genes in P. vivax. We also summarize previous genomic and transcriptomic studies related to the identification of ligand and receptor proteins in P. vivax erythrocyte invasion. Finally, we identify topics that remain unclear and propose future studies that will greatly contribute to our knowledge of P. vivax.