Nancy O. Duah

Bio: Nancy O. Duah is an academic researcher from College of Health Sciences, Bahrain. The author has contributed to research in topics: Plasmodium falciparum & Malaria. The author has an hindex of 19, co-authored 25 publications receiving 1609 citations. Previous affiliations of Nancy O. Duah include University of Ghana & Medical Research Council.

Duration of naturally acquired antibody responses to blood-stage Plasmodium falciparum is age dependent and antigen specific.

Abstract: Naturally acquired antibody responses provide partial protection from clinical malaria, and blood-stage parasite vaccines under development aim to prime such responses. To investigate the determinants of antibody response longevity, immunoglobulin G (IgG) antibodies to several blood-stage vaccine candidate antigens in the sera of two cohorts of children of up to 6 years of age during the dry seasons of 2003 and 2004 in The Gambia were examined. The first cohort showed that most antibodies were lost within less than 4 months of the first sampling if a persistent infection was not present, so the study of the second-year cohort involved collecting samples from individuals every 2 weeks over a 3-month period. Antibody responses in the second cohort were also influenced by persistent malaria infection, so analysis focused particularly on children in whom parasites were not detected after the first time point. Antibodies to most antigens declined more slowly in children in the oldest age group (>5 years old) and more rapidly in children in the youngest group (<3 years old). However, antibodies to merozoite surface protein 2 were shorter lived than antibodies to other antigens and were not more persistent in older children. The age-specific and antigen-specific differences were not explained by different IgG subclass response profiles, indicating the probable importance of differential longevities of plasma cell populations rather than antibody molecules. It is likely that young children mostly have short-lived plasma cells and thus experience rapid declines in antibody levels but that older children have longer-lasting antibody responses that depend on long-lived plasma cells.

Selective Sweeps and Genetic Lineages of Plasmodium falciparum Drug -Resistant Alleles in Ghana

Abstract: Background. In 2005, Ghana adopted artemisinin-based combination therapy (ACT) for primary treatment of falciparum malaria. A comprehensive study of the drug-resistance–associated mutations and their genetic lineages will lead to a better understanding of the evolution of antimalarial drug resistance in this region. Methods. The pfcrt, pfmdr1, dhps, and dhfr mutations associated with chloroquine (CQ) and sulfadoxinepyrimethamine (SP) resistance and the microsatellite loci flanking these genes were genotyped in Plasmodium falciparum isolates from Ghana. Results. The prevalence of mutations associated with both CQ and SP resistance was high in Ghana. However, we observed a decrease in prevalence of the pfcrt K76T mutation in northern Ghana after the change in drug policy from CQ to ACT. Analysis of genetic diversity and differentiation at microsatellite loci flanking all 4 genes indicated that they have been under strong selection, because of CQ and SP use. The triple-mutant pfcrt and dhfr alleles in Ghana were derived from Southeast Asia, whereas the double-mutant dhfr, dhps, and pfmdr1 alleles were of African lineage. Conclusion. Because of the possible role of pfmdr1 in amodiaquine and mefloquine resistance, demonstrating selection on pfmdr1 and defining lineages of resistant alleles in an African population holds great importance.

Manson's Tropical Diseases

Abstract: The first edition of this reference work was published in 1898, and the last update was published in 1972. This current edition is written by six major contributors and contains either rewritten or new chapters, including one 29-page chapter entitled "Ophthalmology in the Tropics" by F. C. Rodger, MD. Not only is this material valuable to physicians in endemic areas, but it is also important for travelers to the tropics who may return home with these diseases. Most of the chapters discuss the following aspects of tropical disease: cause, transmission, immunology, epidemiology, geographical distribution, pathologic condition, clinical findings, and diagnosis (including laboratory findings, treatment, and prevention). Beside chapters on infections, there are chapters on disorders due to heat, nutritional diseases, and venoms and poisons, and appendices on protozoology, helminthology, entomology, and clinical pathologic conditions. Excellent illustrations of end-stage pathologic conditions are disconcerting. Ophthalmologists would be most interested in the discussion

Quinine, an old anti-malarial drug in a modern world: role in the treatment of malaria

Abstract: Quinine remains an important anti-malarial drug almost 400 years after its effectiveness was first documented However, its continued use is challenged by its poor tolerability, poor compliance with complex dosing regimens, and the availability of more efficacious anti-malarial drugs This article reviews the historical role of quinine, considers its current usage and provides insight into its appropriate future use in the treatment of malaria In light of recent research findings intravenous artesunate should be the first-line drug for severe malaria, with quinine as an alternative The role of rectal quinine as pre-referral treatment for severe malaria has not been fully explored, but it remains a promising intervention In pregnancy, quinine continues to play a critical role in the management of malaria, especially in the first trimester, and it will remain a mainstay of treatment until safer alternatives become available For uncomplicated malaria, artemisinin-based combination therapy (ACT) offers a better option than quinine though the difficulty of maintaining a steady supply of ACT in resource-limited settings renders the rapid withdrawal of quinine for uncomplicated malaria cases risky The best approach would be to identify solutions to ACT stock-outs, maintain quinine in case of ACT stock-outs, and evaluate strategies for improving quinine treatment outcomes by combining it with antibiotics In HIV and TB infected populations, concerns about potential interactions between quinine and antiretroviral and anti-tuberculosis drugs exist, and these will need further research and pharmacovigilance

Epidemiology and Infectivity of Plasmodium falciparum and Plasmodium vivax Gametocytes in Relation to Malaria Control and Elimination

Abstract: Malaria remains a major cause of morbidity and mortality in the tropics, with Plasmodium falciparum responsible for the majority of the disease burden and P. vivax being the geographically most widely distributed cause of malaria. Gametocytes are the sexual-stage parasites that infect Anopheles mosquitoes and mediate the onward transmission of the disease. Gametocytes are poorly studied despite this crucial role, but with a recent resurgence of interest in malaria elimination, the study of gametocytes is in vogue. This review highlights the current state of knowledge with regard to the development and longevity of P. falciparum and P. vivax gametocytes in the human host and the factors influencing their distribution within endemic populations. The evidence for immune responses, antimalarial drugs, and drug resistance influencing infectiousness to mosquitoes is reviewed. We discuss how the application of molecular techniques has led to the identification of submicroscopic gametocyte carriage and to a reassessment of the human infectious reservoir. These components are drawn together to show how control measures that aim to reduce malaria transmission, such as mass drug administration and a transmission-blocking vaccine, might better be deployed.