11,294 research outputs found
African origin of the malaria parasite Plasmodium vivax.
No full textPlasmodium vivax is the leading cause of human malaria in Asia and Latin America but is absent from most of central Africa due to the near fixation of a mutation that inhibits the expression of its receptor, the Duffy antigen, on human erythrocytes. The emergence of this protective allele is not understood because P. vivax is believed to have originated in Asia. Here we show, using a non-invasive approach, that wild chimpanzees and gorillas throughout central Africa are endemically infected with parasites that are closely related to human P. vivax. Sequence analyses reveal that ape parasites lack host specificity and are much more diverse than human parasites, which form a monophyletic lineage within the ape parasite radiation. These findings indicate that human P. vivax is of African origin and likely selected for the Duffy-negative mutation. All extant human P. vivax parasites are derived from a single ancestor that escaped out of Africa
Tipificación del antígeno Duffy como método indirecto para identificar individuos asintomáticos de malaria
No full textEn países considerados endémicos de malaria a pesar de las estrategias realizadas anualmente para el control y erradicación de esta enfermedad existen brotes aislados de malaria debido probablemente a portadores asintomáticos, presencia de individuos con fenotipo Duffy negativo o movimientos poblacionales. El sector “50 casas” de la provincia de Esmeraldas-Ecuador reúne todas estas características por lo que el objetivo de esta investigación fue determinar la presencia del fenotipo Fy(a-b-) y su relación con el Plasmodium vivax. Se realizó una encuesta a cada miembro de las familias participantes y luego de aceptado y firmado el consentimiento informado se tomaron muestras sanguíneas para la realización de pruebas serológicas en búsqueda de anticuerpos y antígenos de P. vivax, fenotipificación del sistema Duffy y pruebas de PCR en tiempo real para la determinación de ADN de Plasmodium vivax y P. falciparum. Los resultados demostraron que existe una asociación estadísticamente significativa entre el fenotipo Duffy y malaria por P. vivax (p<0,05). Ante esta situación los organismos de control deberán proponer nuevas estrategias para la detección de portadores asintomáticos y medidas preventivas para evitar nuevos brotes de malaria, así como determinar si P. vivax ha encontrado un nuevo mecanismo de invasión en individuos portadores del fenotipo Fy(a-b-)
Tipificación del antígeno Duffy como método indirecto para identificar individuos asintomáticos de malaria
No full textEn países considerados endémicos de malaria a pesar de las estrategias realizadas anualmente para el control y erradicación de esta enfermedad existen brotes aislados de malaria debido probablemente a portadores asintomáticos, presencia de individuos con fenotipo Duffy negativo o movimientos poblacionales. El sector “50 casas” de la provincia de Esmeraldas-Ecuador reúne todas estas características por lo que el objetivo de esta investigación fue determinar la presencia del fenotipo Fy(a-b-) y su relación con el Plasmodium vivax. Se realizó una encuesta a cada miembro de las familias participantes y luego de aceptado y firmado el consentimiento informado se tomaron muestras sanguíneas para la realización de pruebas serológicas en búsqueda de anticuerpos y antígenos de P. vivax, fenotipificación del sistema Duffy y pruebas de PCR en tiempo real para la determinación de ADN de Plasmodium vivax y P. falciparum. Los resultados demostraron que existe una asociación estadísticamente significativa entre el fenotipo Duffy y malaria por P. vivax (p<0,05). Ante esta situación los organismos de control deberán proponer nuevas estrategias para la detección de portadores asintomáticos y medidas preventivas para evitar nuevos brotes de malaria, así como determinar si P. vivax ha encontrado un nuevo mecanismo de invasión en individuos portadores del fenotipo Fy(a-b-)
Reduced risk of Plasmodium vivax malaria in Papua New Guinean children with Southeast Asian ovalocytosis in two cohorts and a case-control study
No full textBACKGROUND: The erythrocyte polymorphism, Southeast Asian ovalocytosis (SAO) (which results from a 27-base pair deletion in the erythrocyte band 3 gene, SLC4A1Delta27) protects against cerebral malaria caused by Plasmodium falciparum; however, it is unknown whether this polymorphism also protects against P. vivax infection and disease. METHODS AND FINDINGS: The association between SAO and P. vivax infection was examined through genotyping of 1,975 children enrolled in three independent epidemiological studies conducted in the Madang area of Papua New Guinea. SAO was associated with a statistically significant 46% reduction in the incidence of clinical P. vivax episodes (adjusted incidence rate ratio [IRR] = 0.54, 95% CI 0.40-0.72, p>0.0001) in a cohort of infants aged 3-21 months and a significant 52% reduction in P. vivax (blood-stage) reinfection diagnosed by PCR (95% CI 22-71, p = 0.003) and 55% by light microscopy (95% CI 13-77, p = 0.014), respectively, in a cohort of children aged 5-14 years. SAO was also associated with a reduction in risk of P. vivax parasitaemia in children 3-21 months (1,111/microl versus 636/microl, p = 0.011) and prevalence of P. vivax infections in children 15-21 months (odds ratio [OR] = 0.39, 95% CI 0.23-0.67, p = 0.001). In a case-control study of children aged 0.5-10 years, no child with SAO was found among 27 cases with severe P. vivax or mixed P. falciparum/P. vivax malaria (OR = 0, 95% CI 0-1.56, p = 0.11). SAO was associated with protection against severe P. falciparum malaria (OR = 0.38, 95% CI 0.15-0.87, p = 0.014) but no effect was seen on either the risk of acquiring blood-stage infections or uncomplicated episodes with P. falciparum. Although Duffy antigen receptor expression and function were not affected on SAO erythrocytes compared to non-SAO children, high level (<90% binding inhibition) P. vivax Duffy binding protein-specific binding inhibitory antibodies were observed significantly more often in sera from SAO than non-SAO children (SAO, 22.2%; non-SAO, 6.7%; p = 0.008). CONCLUSIONS: In three independent studies, we observed strong associations between SAO and protection against P. vivax malaria by a mechanism that is independent of the Duffy antigen. P. vivax malaria may have contributed to shaping the unique host genetic adaptations to malaria in Asian and Oceanic populations. Please see later in the article for the Editors' Summar
Duffy, P M, 54477
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/382807Surname: DUFFY. Given Name(s) or Initials: P M. Military Service Number or Last Known Location: 54477. Missing, Wounded and Prisoner of War Enquiry Card Index Number: SEA-1717.222454
Item: [2016.0049.15100] "Duffy, P M, 54477
Duffy, J P, NX18121
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/382812Surname: DUFFY. Given Name(s) or Initials: J P. Military Service Number or Last Known Location: NX18121. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 2975.222459
Item: [2016.0049.15105] "Duffy, J P, NX18121
The Origins of African Plasmodium vivax; Insights from Mitochondrial Genome Sequencing
No full textPlasmodium vivax, the second most prevalent of the human malaria parasites, is estimated to affect 75 million people annually. It is very rare, however, in west and central Africa, due to the high prevalence of the Duffy negative phenotype in the human population. Due to its rarity in Africa, previous studies on the phylogeny of world-wide P. vivax have suffered from insufficient samples of African parasites. Here we compare the mitochondrial sequence diversity of parasites from Africa with those from other areas of the world, in order to investigate the origin of present-day African P. vivax. Mitochondrial genome sequencing revealed relatively little polymorphism within the African population compared to parasites from the rest of the world. This, combined with sequence similarity with parasites from India, suggests that the present day African P. vivax population in humans may have been introduced relatively recently from the Indian subcontinent. Haplotype network analysis also raises the possibility that parasites currently found in Africa and South America may be the closest extant relatives of the ancestors of the current world population. Lines of evidence are adduced that this ancestral population may be from an ancient stock of P. vivax in Africa.</p
Reduced Plasmodium vivax erythrocyte infection in PNG Duffy-negative heterozygotes.
No full textErythrocyte Duffy blood group negativity reaches fixation in African populations where Plasmodium vivax (Pv) is uncommon. While it is known that Duffy-negative individuals are highly resistant to Pv erythrocyte infection, little is known regarding Pv susceptibility among heterozygous carriers of a Duffy-negative allele (+/-). Our limited knowledge of the selective advantages or disadvantages associated with this genotype constrains our understanding of the effect that interventions against Pv may have on the health of people living in malaria-endemic regions.We conducted cross-sectional malaria prevalence surveys in Papua New Guinea (PNG), where we have previously identified a new Duffy-negative allele among individuals living in a region endemic for all four human malaria parasite species. We evaluated infection status by conventional blood smear light microscopy and semi-quantitative PCR-based strategies. Analysis of a longitudinal cohort constructed from our surveys showed that Duffy heterozygous (+/-) individuals were protected from Pv erythrocyte infection compared to those homozygous for wild-type alleles (+/+) (log-rank tests: LM, p = 0.049; PCR, p = 0.065). Evaluation of Pv parasitemia, determined by semi-quantitative PCR-based methods, was significantly lower in Duffy +/- vs. +/+ individuals (Mann-Whitney U: p = 0.023). Overall, we observed no association between susceptibility to P. falciparum erythrocyte infection and Duffy genotype.Our findings provide the first evidence that Duffy-negative heterozygosity reduces erythrocyte susceptibility to Pv infection. As this reduction was not associated with greater susceptibility to Pf malaria, our in vivo observations provide evidence that Pv-targeted control measures can be developed safely
The Influence of Data Density on the Consistency of Performance of the Feature Selective Validation (FSV) Technique
No full textProfessor Alan Duffy and Dr Amanda Caples on a graphene-enabled future for Australia
No full textProfessor Alan Duffy chats with Victoria’s Lead Scientist Dr Amanda Caples about the future of Graphene and why it’s a key part of Industry 4.0.</p
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