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Molecular entomology and prospects for malaria control
Collins,Frank H.; Kamau,Luna; Ranson,Hilary A.; Vulule,John M.;
Bulletin of the World Health Organization , 2000, DOI: 10.1590/S0042-96862000001200008
Abstract: during the past decade, the techniques of molecular and cell biology have been embraced by many scientists doing research on anopheline vectors of malaria parasites. some of the most important research advances in molecular entomology have concerned the development of sophisticated molecular tools for procedures such as genetic and physical mapping and germ line transformation. major advances have also been made in the study of specific biological processes such as insect defence against pathogens and the manner in which malaria parasites and their anopheline hosts interact during sporogony. one of the most important highlights of this research trend has been the emergence during the past year of a formal international anopheles gambiae genome project, which at present includes investigators in several laboratories in europe and the usa. although much of this molecular research is directed towards the development of malaria control strategies that are probably many years from implementation, there are some important areas of molecular entomology that may have a more near-term impact on malaria control. we highlight developments over the past decade in three such areas that we believe can make important contributions to the development of near-term malaria control strategies. these areas are anopheline species identification, the detection and monitoring of insecticide susceptibility/resistance in wild anopheline populations and the determination of the genetic structure of anopheline populations.
Molecular entomology and prospects for malaria control  [cached]
Collins Frank H.,Kamau Luna,Ranson Hilary A.,Vulule John M.
Bulletin of the World Health Organization , 2000,
Abstract: During the past decade, the techniques of molecular and cell biology have been embraced by many scientists doing research on anopheline vectors of malaria parasites. Some of the most important research advances in molecular entomology have concerned the development of sophisticated molecular tools for procedures such as genetic and physical mapping and germ line transformation. Major advances have also been made in the study of specific biological processes such as insect defence against pathogens and the manner in which malaria parasites and their anopheline hosts interact during sporogony. One of the most important highlights of this research trend has been the emergence during the past year of a formal international Anopheles gambiae genome project, which at present includes investigators in several laboratories in Europe and the USA. Although much of this molecular research is directed towards the development of malaria control strategies that are probably many years from implementation, there are some important areas of molecular entomology that may have a more near-term impact on malaria control. We highlight developments over the past decade in three such areas that we believe can make important contributions to the development of near-term malaria control strategies. These areas are anopheline species identification, the detection and monitoring of insecticide susceptibility/resistance in wild anopheline populations and the determination of the genetic structure of anopheline populations.
Transmission dynamics of malaria in Nigeria.
OO Okwa, FI Akinmolayan, V Carter, H Hurd
Annals of African Medicine , 2009,
Abstract: Background: Two of the problems of malaria parasite vector control in Nigeria are the diversity of Anopheline vectors and large size of the country. Anopheline distribution and transmission dynamics of malaria were therefore compared between four ecotypes in Nigeria during the rainy season. Methods: Polymerase chain reaction (PCR) was used in molecular identification after morphological identification microscopically. Enzyme linked immunorsorbent assay (ELISA) was used for the blood meal analysis and sporozoite detection. Results: Five species were identified out of 16,410 anophelines collected. An. gambiae s.s made up approximately 29.2%-36.6% of the population in each zone. All five species acted as vectors for P. falciparum. An. gambiae s.s had the highest sporozoite rate. The most infected mosquitoes were found in the rain forest. More blood meals were taken from bovids, except the savannah forest, where 73.3% were on humans and Human Blood index (HBI) was 57.3%. The Entomological inoculation rate (EIR) was a mean of 13.6 ib/p but was highest in the rainforest zone. Conclusions and limitations: This study demonstrates the complex distribution of anophelines and the considerable variations in the intensity of malaria transmission in Nigeria. We highlight the need to consider diverse epidemiological situations when planning countrywide control programmes.
Transmission Dynamics of Malaria in Ghana  [cached]
Francis Oduro,Gabriel A. Okyere,George Theodore Azu-Tungmah
Journal of Mathematics Research , 2012, DOI: 10.5539/jmr.v4n6p22
Abstract: In this paper, a deterministic mathematical model to investigate the transmission dynamics of malaria in Ghana is formulated taking into account human and mosquito populations. The model consists of seven non-linear differential equations which describe the dynamics of malaria with 4 variables for humans and 3 variables for mosquitoes. The state vector for the model is $(S_h, E_h, I_h, R, S_m, E_m, I_m,)$ where $S_h$, $E_h$, $I_h$, $R$, $S_m$, $E_m$ and $I_m$ respectively represent populations of susceptible humans, exposed humans, infectious humans, recovered humans, susceptible mosquitoes, exposed mosquitoes and infectious mosquitoes. Stability analysis of the model is performed and we make use of the next generation method to derive the basic reproduction number $R_0$. A mathematical analysis of the dynamic behaviour indicates that the estimated model has a unique endemic equilibrium point and malaria will persist in Ghana. The basic reproduction number for Ghana is found to be $R_0=0.8939$. Further, both the disease-free and endemic equilibria are locally asymptotically stable. Numerical simulations indicate that reducing current biting rate of female Anopheles mosquitoes by 1/16 could assist Ghana to achieve malaria free status by the year 2037. If, in addition, the number of days it takes to recover from malaria infection were reduced to three 3 days malaria free status could be achieved by the year 2029.
The prospect of eliminating malaria transmission in some regions of Brazil
Tauil, Pedro Luiz;
Memórias do Instituto Oswaldo Cruz , 2011, DOI: 10.1590/S0074-02762011000900013
Abstract: this paper discusses malaria epidemiology and control in brazil as well as the prospect of interrupting transmission in some areas of the country. the concepts of receptivity and vulnerability of an area to malaria transmission are analysed to predict where elimination might occur in a near future. outside of the amazon region and in the oriental states of the amazon, such as tocantins, maranh?o and mato grosso, it is likely that malaria transmission can be eliminated with the development and sustained use of a good surveillance system.
Quantifying Transmission Investment in Malaria Parasites  [PDF]
Megan A. Greischar?,Nicole Mideo?,Andrew F. Read?,Ottar N. Bj?rnstad
PLOS Computational Biology , 2016, DOI: 10.1371/journal.pcbi.1004718
Abstract: Many microparasites infect new hosts with specialized life stages, requiring a subset of the parasite population to forgo proliferation and develop into transmission forms. Transmission stage production influences infectivity, host exploitation, and the impact of medical interventions like drug treatment. Predicting how parasites will respond to public health efforts on both epidemiological and evolutionary timescales requires understanding transmission strategies. These strategies can rarely be observed directly and must typically be inferred from infection dynamics. Using malaria as a case study, we test previously described methods for inferring transmission stage investment against simulated data generated with a model of within-host infection dynamics, where the true transmission investment is known. We show that existing methods are inadequate and potentially very misleading. The key difficulty lies in separating transmission stages produced by different generations of parasites. We develop a new approach that performs much better on simulated data. Applying this approach to real data from mice infected with a single Plasmodium chabaudi strain, we estimate that transmission investment varies from zero to 20%, with evidence for variable investment over time in some hosts, but not others. These patterns suggest that, even in experimental infections where host genetics and other environmental factors are controlled, parasites may exhibit remarkably different patterns of transmission investment.
Effect of malaria on HIV/AIDS transmission and progression
Alemu Abebe,Shiferaw Yitayal,Addis Zelalem,Mathewos Biniam
Parasites & Vectors , 2013, DOI: 10.1186/1756-3305-6-18
Abstract: Malaria and HIV are among the two most important global health problems of developing countries. They cause more than 4 million deaths a year. These two infections interact bidirectionally and synergistically with each other. HIV infection increases the risk of an increase in the severity of malaria infection and burdens of malaria, which in turn facilitates the rate of malaria transmission. Malaria infection is also associated with strong CD4+ cell activation and up-regulation of proinflammatory cytokines and it provides an ideal microenvironment for the spread of the virus among the CD4+ cells and for rapid HIV-1 replication. Additionally, malaria increases blood viral burden by different mechanisms. Therefore, high concentrations of HIV-1 RNA in the blood are predictive of disease progression, and correlate with the risk of blood-borne, vertical, and sexual transmission of the virus. Therefore, this article aims to review information about HIV malaria interactions, the effect of malaria on HIV transmission and progression and the implications related to prevention and treatment of coinfection.
Can slide positivity rates predict malaria transmission?
Yan Bi, Wenbiao Hu, Huaxin Liu, Yujiang Xiao, Yuming Guo, Shimei Chen, Laifa Zhao, Shilu Tong
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-117
Abstract: Data on annual malaria cases, SPR and socio-economic factors for the period of 1993 to 2008 were obtained from the Center for Disease Control and Prevention (CDC) and the Bureau of Statistics, Mengla, China. Multiple linear regression models were conducted to evaluate the relationship between socio-ecologic factors and malaria incidence.The results show that SPR was significantly positively associated with the malaria incidence rates. The SPR (β?=?1.244, p?=?0.000) alone and combination (SPR, β?=?1.326, p?<?0.001) with other predictors can explain about 85% and 95% of variation in malaria transmission, respectively. Every 1% increase in SPR corresponded to an increase of 1.76/100,000 in malaria incidence rates.SPR is a strong predictor of malaria transmission, and can be used to improve the planning and implementation of malaria elimination programmes in Mengla and other similar locations. SPR might also be a useful indicator of malaria early warning systems in China.
Malaria Morbidity in High and Seasonal Malaria Transmission Area of Burkina Faso  [PDF]
Alphonse Ouédraogo, Alfred B. Tiono, Amidou Diarra, Souleymane Sanon, Jean Baptiste Yaro, Esperance Ouedraogo, Edith C. Bougouma, Issiaka Soulama, Adama Gansané, Amathe Ouedraogo, Amadou T. Konate, Issa Nebie, Nora L. Watson, Megan Sanza, Tina J. T. Dube, Sodiomon Bienvenu Sirima
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0050036
Abstract: Background Malariometric parameters are often primary endpoints of efficacy trials of malaria vaccine candidates. This study aims to describe the epidemiology of malaria prior to the conduct of a series of drug and vaccine trials in a rural area of Burkina Faso. Methods Malaria incidence was prospectively evaluated over one year follow-up among two cohorts of children aged 0–5 years living in the Saponé health district. The parents of 1089 children comprising a passive case detection cohort were encouraged to seek care from the local health clinic at any time their child felt sick. Among this cohort, 555 children were randomly selected for inclusion in an active surveillance sub-cohort evaluated for clinical malaria during twice weekly home visits. Malaria prevalence was evaluated by cross-sectional survey during the low and high transmission seasons. Results Number of episodes per child ranged from 0 to 6 per year. Cumulative incidence was 67.4% in the passive and 86.2% in the active cohort and was highest among children 0–1 years. Clinical malaria prevalence was 9.8% in the low and 13.0% in the high season (p>0.05). Median days to first malaria episode ranged from 187 (95% CI 180–193) among children 0–1 years to 228 (95% CI 212, 242) among children 4–5 years. The alternative parasite thresholds for the malaria case definition that achieved optimal sensitivity and specificity (70–80%) were 3150 parasites/μl in the high and 1350 parasites/μl in the low season. Conclusion Clinical malaria burden was highest among the youngest age group children, who may represent the most appropriate target population for malaria vaccine candidate development. The pyrogenic threshold of parasitaemia varied markedly by season, suggesting a value for alternative parasitaemia levels in the malaria case defintion. Regional epidemiology of malaria described, Sapone area field centers are positioned for future conduct of malaria vaccine trials.
Malaria transmission modelling: a network perspective
Jiming Liu, Bo Yang, William K Cheung, Guojing Yang
Infectious Diseases of Poverty , 2012, DOI: 10.1186/2049-9957-1-11
Abstract: Please see Additional file 1 for translations of the abstract into the six official working languages of the United Nations.Malaria transmission is challenging to model; its vector can be quite complex due to topographical and climatic variations as well as human mobility [1]. One of the United Nations (UN) Millennium Development Goals is to “have halted by 2015 and begun to reverse the incidence of malaria” which annually causes ~1 million death or >1 death every 30–60 second [2,3]. World Health Organization (WHO) has suggested that the most important measure is a timely response with the implementation of effective interventions once it has been detected [4]. This requires an effective monitoring/surveillance system that can provide long range forecasting, early warning, and early detection [5]. Towards this end, malaria transmission patterns will be informative in performing such surveillance functions.This article provides a review of related work on how to develop a computational means for inferring malaria transmission networks in populations, which incorporates: (1) partial surveillance data over time, i.e., the temporal-spatial distributions of cases of infection, and (2) infection models of malaria. A transmission network to characterize the temporal-spatial patterns of disease transmission, or a temporal-spatial disease transmission network, consists of a set of nodes and a set of links that connect them, where the nodes correspond to spatial locations, such as villages, with reported/observed disease incidences over time, and the directional links connecting the nodes correspond to the probability/likelihood of disease “transmission” from one node to another over time, e.g., hidden pathways of malaria transmission.Technically, the problem of computationally inferring malaria transmission networks is both interesting and challenging because, during the process of disease spread, the reported infection cases do not directly reflect the full extent of transm
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