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Keirsebelik MSG, David MR, Pavan MG, Couto-Lima D, Palomino M, Rahman RU, Hoffmann AA, Bahia AC, Caljon G, Maciel-de-Freitas R. Dengue Virus Serotype 1 Effects on Mosquito Survival Differ among Geographically Distinct Aedes aegypti Populations. INSECTS 2024; 15:393. [PMID: 38921108 PMCID: PMC11203567 DOI: 10.3390/insects15060393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 05/17/2024] [Accepted: 05/21/2024] [Indexed: 06/27/2024]
Abstract
The mosquito Aedes aegypti is distributed worldwide and is recognized as the primary vector for dengue in numerous countries. To investigate whether the fitness cost of a single DENV-1 isolate varies among populations, we selected four Ae. aegypti populations from distinct localities: Australia (AUS), Brazil (BRA), Pakistan (PAK), and Peru (PER). Utilizing simple methodologies, we concurrently assessed survival rates and fecundity. Overall, DENV-1 infection led to a significant decrease in mosquito survival rates, with the exception of the PER population. Furthermore, infected Ae. aegypti from PAK, the population with the lowest infection rate among those tested, exhibited a noteworthy reduction in egg laying. These findings collectively suggest that local mosquito-virus adaptations may influence dengue transmission in endemic settings.
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Affiliation(s)
- Milan S. G. Keirsebelik
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro 21040-900, Brazil; (M.S.G.K.); (M.R.D.); (M.G.P.); (D.C.-L.)
- Laboratory of Microbiology, Parasitology and Hygiene, University of Antwerp, 1, 2610 Wilrijk-Antwerp, Belgium;
| | - Mariana R. David
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro 21040-900, Brazil; (M.S.G.K.); (M.R.D.); (M.G.P.); (D.C.-L.)
| | - Márcio Galvão Pavan
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro 21040-900, Brazil; (M.S.G.K.); (M.R.D.); (M.G.P.); (D.C.-L.)
| | - Dinair Couto-Lima
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro 21040-900, Brazil; (M.S.G.K.); (M.R.D.); (M.G.P.); (D.C.-L.)
| | - Miriam Palomino
- Laboratorio de Referência Nacional de Entomologia, Centro Nacional de Salud Pública, Instituto Nacional de Salud, Lima 15072, Peru;
| | - Rafi Ur Rahman
- Department of Biosciences, COMSATS University, Islamabad 45550, Pakistan;
| | - Ary A. Hoffmann
- Pest and Environmental Adaptation Research Group, Bio21 Institute, School of BioSciences, The University of Melbourne, 3052 Melbourne, Australia;
| | - Ana C. Bahia
- Laboratório de Bioquímica de Insetos e Parasitos, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21040-900, Brazil;
| | - Guy Caljon
- Laboratory of Microbiology, Parasitology and Hygiene, University of Antwerp, 1, 2610 Wilrijk-Antwerp, Belgium;
| | - Rafael Maciel-de-Freitas
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro 21040-900, Brazil; (M.S.G.K.); (M.R.D.); (M.G.P.); (D.C.-L.)
- Bernhard Nocht Institute for Tropical Medicine, 20359 Hamburg, Germany
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Maraschin M, Talyuli OAC, Luíza Rulff da Costa C, Granella LW, Moi DA, Figueiredo BRS, Mansur DS, Oliveira PL, Oliveira JHM. Exploring dose-response relationships in Aedes aegypti survival upon bacteria and arbovirus infection. JOURNAL OF INSECT PHYSIOLOGY 2023; 151:104573. [PMID: 37838284 DOI: 10.1016/j.jinsphys.2023.104573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 10/06/2023] [Accepted: 10/10/2023] [Indexed: 10/16/2023]
Abstract
A detailed understanding of how host fitness changes in response to variations in microbe density (an ecological measure of disease tolerance) is an important aim of infection biology. Here, we applied dose-response curves to study Aedes aegypti survival upon exposure to different microbes. We challenged female mosquitoes with Listeria monocytogenes, a model bacterial pathogen, Dengue 4 virus and Zika virus, two medically relevant arboviruses, to understand the distribution of mosquito survival following microbe exposure. By correlating microbe loads and host health, we found that a blood meal promotes disease tolerance in our systemic bacterial infection model and that mosquitoes orally infected with bacteria had an enhanced defensive capacity than insects infected through injection. We also showed that Aedes aegypti displays a higher survival profile following arbovirus infection when compared to bacterial infections. Here, we applied a framework for investigating microbe-induced mosquito mortality and details how the lifespan of Aedes aegypti varies with different inoculum sizes of bacteria and arboviruses.
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Affiliation(s)
- Mariana Maraschin
- Departamento de Microbiologia, Imunologia e Parasitologia. Universidade Federal de Santa Catarina. Florianópolis, Brazil
| | - Octávio A C Talyuli
- Instituto de Bioquímica Médica Leopoldo de Meis. Universidade Federal do Rio de Janeiro. Rio de Janeiro, Brazil
| | - Clara Luíza Rulff da Costa
- Instituto de Bioquímica Médica Leopoldo de Meis. Universidade Federal do Rio de Janeiro. Rio de Janeiro, Brazil
| | - Lucilene W Granella
- Departamento de Microbiologia, Imunologia e Parasitologia. Universidade Federal de Santa Catarina. Florianópolis, Brazil
| | - Dieison A Moi
- Laboratory of Multitrophic Interactions and Biodiversity, Department of Animal Biology, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP 13083-862, Brazil
| | - Bruno R S Figueiredo
- Graduate Program in Ecology, Department of Ecology and Zoology, Federal University of Santa Catarina, Campus Universitário, Edifício Fritz Müller, Bloco B, Córrego Grande, CEP 88040-970, Florianópolis, Santa Catarina, Brazil
| | - Daniel S Mansur
- Departamento de Microbiologia, Imunologia e Parasitologia. Universidade Federal de Santa Catarina. Florianópolis, Brazil
| | - Pedro L Oliveira
- Instituto de Bioquímica Médica Leopoldo de Meis. Universidade Federal do Rio de Janeiro. Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular. Brazil
| | - José Henrique M Oliveira
- Departamento de Microbiologia, Imunologia e Parasitologia. Universidade Federal de Santa Catarina. Florianópolis, Brazil; Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular. Brazil.
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Li HH, Su MP, Wu SC, Tsou HH, Chang MC, Cheng YC, Tsai KN, Wang HW, Chen GH, Tang CK, Chung PJ, Tsai WT, Huang LR, Yueh YA, Chen HW, Pan CY, Akbari OS, Chang HH, Yu GY, Marshall JM, Chen CH. Mechanical transmission of dengue virus by Aedes aegypti may influence disease transmission dynamics during outbreaks. EBioMedicine 2023; 94:104723. [PMID: 37487418 PMCID: PMC10382859 DOI: 10.1016/j.ebiom.2023.104723] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 07/02/2023] [Accepted: 07/06/2023] [Indexed: 07/26/2023] Open
Abstract
BACKGROUND Dengue virus outbreaks are increasing in number and severity worldwide. Viral transmission is assumed to require a minimum time period of viral replication within the mosquito midgut. It is unknown if alternative transmission periods not requiring replication are possible. METHODS We used a mouse model of dengue virus transmission to investigate the potential of mechanical transmission of dengue virus. We investigated minimal viral titres necessary for development of symptoms in bitten mice and used resulting parameters to inform a new model of dengue virus transmission within a susceptible population. FINDINGS Naïve mice bitten by mosquitoes immediately after they took partial blood meals from dengue infected mice showed symptoms of dengue virus, followed by mortality. Incorporation of mechanical transmission into mathematical models of dengue virus transmission suggest that this supplemental transmission route could result in larger outbreaks which peak sooner. INTERPRETATION The potential of dengue transmission routes independent of midgut viral replication has implications for vector control strategies that target mosquito lifespan and suggest the possibility of similar mechanical transmission routes in other disease-carrying mosquitoes. FUNDING This study was funded by grants from the National Health Research Institutes, Taiwan (04D2-MMMOST02), the Human Frontier Science Program (RGP0033/2021), the National Institutes of Health (1R01AI143698-01A1, R01AI151004 and DP2AI152071) and the Ministry of Science and Technology, Taiwan (MOST104-2321-B-400-016).
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Affiliation(s)
- Hsing-Han Li
- National Mosquito-Borne Disease Control Research Center, NHRI, Miaoli, 350401, Taiwan; National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan; Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Matthew P Su
- Graduate School of Science, Nagoya University, Nagoya, 464-8602, Japan; Institute for Advanced Research, Nagoya University, Nagoya, 464-8601, Japan
| | - Shih-Cheng Wu
- National Mosquito-Borne Disease Control Research Center, NHRI, Miaoli, 350401, Taiwan; National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan; Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, 10048, Taiwan; Department of Laboratory Medicine, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, 10021, Taiwan
| | - Hsiao-Hui Tsou
- Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Miaoli, 350401, Taiwan; Graduate Institute of Biostatistics, College of Public Health, China Medical University, Taichung, 40402, Taiwan
| | - Meng-Chun Chang
- Department of Life Science & Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan
| | - Yu-Chieh Cheng
- Institute of Population Health Sciences, National Health Research Institutes, Zhunan, Miaoli, 350401, Taiwan
| | - Kuen-Nan Tsai
- Institute of Molecular and Genomic Medicine, NHRI, Miaoli, 350401, Taiwan
| | - Hsin-Wei Wang
- National Mosquito-Borne Disease Control Research Center, NHRI, Miaoli, 350401, Taiwan; National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan
| | - Guan-Hua Chen
- National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan; Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 300, Taiwan
| | - Cheng-Kang Tang
- National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan; Program of Plant Protection and Health, Academy of Circular Economy, National Chung Hsing University, Taichung, 402202, Taiwan
| | - Pei-Jung Chung
- National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan
| | - Wan-Ting Tsai
- National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan
| | - Li-Rung Huang
- Institute of Molecular and Genomic Medicine, NHRI, Miaoli, 350401, Taiwan
| | - Yueh Andrew Yueh
- Institute of Biotechnology and Pharmaceutical Research, NHRI, Miaoli, 350401, Taiwan
| | - Hsin-Wei Chen
- National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan
| | - Chao-Ying Pan
- Department of Health, Kaohsiung City Government, Kaohsiung, 800852, Taiwan
| | - Omar S Akbari
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Hsiao-Han Chang
- Department of Life Science & Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu, Taiwan
| | - Guann-Yi Yu
- National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan
| | - John M Marshall
- Divisions of Biostatistics and Epidemiology, School of Public Health, University of California, Berkeley, CA, 94720, USA
| | - Chun-Hong Chen
- National Mosquito-Borne Disease Control Research Center, NHRI, Miaoli, 350401, Taiwan; National Institute of Infectious Diseases and Vaccinology, NHRI, Miaoli, 350401, Taiwan.
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Ismail S, Fildes R, Ahmad R, Wan Mohamad Ali WN, Omar T. The practicality of Malaysia dengue outbreak forecasting model as an early warning system. Infect Dis Model 2022; 7:510-525. [PMID: 36091345 PMCID: PMC9418377 DOI: 10.1016/j.idm.2022.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 07/07/2022] [Accepted: 07/30/2022] [Indexed: 11/26/2022] Open
Abstract
Dengue is a harmful tropical disease that causes death to many people. Currently, the dengue vaccine development is still at an early stage, and only intervention methods exist after dengue cases increase. Thus, previously, two scientific experimental field studies were conducted in producing a dengue outbreak forecasting model as an early warning system. Successfully, an Autoregressive Distributed Lag (ADL) Model was developed using three factors: the epidemiological, entomological, and environmental with an accuracy of 85%; but a higher percentage is required in minimizing the error for the model to be useful. Hence, this study aimed to develop a practical and cost-effective dengue outbreak forecasting model with at least 90% accuracy to be embedded in an early warning computer system using the Internet of Things (IoT) approach. Eighty-one weeks of time series data of the three factors were used in six forecasting models, which were Autoregressive Distributed Lag (ADL), Hierarchical Forecasting (Bottom-up and Optimal combination) and three Machine Learning methods: (Artificial Neural Network (ANN), Support Vector Machine (SVM) and Random Forest). Five error measures were used to evaluate the consistency performance of the models in order to ensure model performance. The findings indicated Random Forest outperformed the other models with an accuracy of 95% when including all three factors. But practically, collecting mosquito related data (the entomological factor) was very costly and time consuming. Thus, it was removed from the model, and the accuracy dropped to 92% but still high enough to be of practical use, i.e., beyond 90%. However, the practical ground operationalization of the early warning system also requires several rain gauges to be located at the dengue hot spots due to localized rainfall. Hence, further analysis was conducted in determining the location of the rain gauges. This has led to the recommendation that the rain gauges should be located about 3–4 km apart at the dengue hot spots to ensure the accuracy of the rainfall data to be included in the dengue outbreak forecasting model so that it can be embedded in the early warning system. Therefore, this early warning system can save lives, and prevention is better than cure.
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5
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Mathematical modeling in perspective of vector-borne viral infections: a review. BENI-SUEF UNIVERSITY JOURNAL OF BASIC AND APPLIED SCIENCES 2022; 11:102. [PMID: 36000145 PMCID: PMC9388993 DOI: 10.1186/s43088-022-00282-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Accepted: 08/08/2022] [Indexed: 11/27/2022] Open
Abstract
Background Viral diseases are highly widespread infections caused by viruses. These viruses are passing from one human to other humans through a certain medium. The medium might be mosquito, animal, reservoir and food, etc. Here, the population of both human and mosquito vectors are important. Main body of the abstract The main objectives are here to introduce the historical perspective of mathematical modeling, enable the mathematical modeler to understand the basic mathematical theory behind this and present a systematic review on mathematical modeling for four vector-borne viral diseases using the deterministic approach. Furthermore, we also introduced other mathematical techniques to deal with vector-borne diseases. Mathematical models could help forecast the infectious population of humans and vectors during the outbreak. Short conclusion This study will be helpful for mathematical modelers in vector-borne diseases and ready-made material in the review for future advancement in the subject. This study will not only benefit vector-borne conditions but will enable ideas for other illnesses.
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Gubbins S. Using the basic reproduction number to assess the risk of transmission of lumpy skin disease virus by biting insects. Transbound Emerg Dis 2019; 66:1873-1883. [PMID: 31038286 PMCID: PMC6767157 DOI: 10.1111/tbed.13216] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 04/24/2019] [Accepted: 04/25/2019] [Indexed: 01/23/2023]
Abstract
In recent years, lumpy skin disease virus (LSDV) has emerged as a major threat to cattle outside Africa, where it is endemic. Although evidence suggests that LSDV is transmitted by the bites of blood sucking arthropods, few studies have assessed the risk of transmission posed by particular vector species. Here this risk is assessed by calculating the basic reproduction number (R0 ) for transmission of LSDV by five species of biting insect: the stable fly, Stomoxys calcitrans, the biting midge, Culicoides nubeculosus, and three mosquito species, Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Parameters relating to mechanical transmission of LSDV were estimated using new analyses of previously published data from transmission experiments, while vector life history parameters were derived from the published literature. Uncertainty and sensitivity analyses were used to compute R0 for each species and to identify those parameters which influence its magnitude. Results suggest that S. calcitrans is likely to be the most efficient at transmitting LSDV, with Ae. aegypti also an efficient vector. By contrast, C. nubeculosus, An. stephensi, and Cx. quinquefasciatus are likely to be inefficient vectors of LSDV. However, there is considerable uncertainty associated with the estimates of R0 , reflecting uncertainty in most of the constituent parameters. Sensitivity analysis suggests that future experimental work should focus on estimating the probability of transmission from insect to bovine and on the virus inactivation rate in insects.
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Chen CWS, Khamthong K, Lee S. Markov switching integer‐valued generalized auto‐regressive conditional heteroscedastic models for dengue counts. J R Stat Soc Ser C Appl Stat 2019. [DOI: 10.1111/rssc.12344] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Saad FT, Sanlidag T, Hincal E, Sayan M, Baba IA, Kaymakamzade B. Global Stability Analysis of HIV+ Model. 13TH INTERNATIONAL CONFERENCE ON THEORY AND APPLICATION OF FUZZY SYSTEMS AND SOFT COMPUTING — ICAFS-2018 2019. [PMCID: PMC7122938 DOI: 10.1007/978-3-030-04164-9_109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We developed and studied a mathematical model of HIV+. Two equilibriums points were found, disease free and endemic equilibrium, and basic reproduction ratio \documentclass[12pt]{minimal}
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\begin{document}$$ R_{0} $$\end{document}R0 was also calculated by the use of next generation matrix. Global stability analysis of the equilibria was carried out by the use of Lyapunov function, and it was shown that the stability of the equilibria depends on the magnitude of the basic reproduction ratio. When \documentclass[12pt]{minimal}
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\begin{document}$$ R_{0} < 1 $$\end{document}R0<1, the disease free equilibrium is globally asymptotically stable, and disease dies out. On the other hand if \documentclass[12pt]{minimal}
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\begin{document}$$ R_{0} \ge 1 $$\end{document}R0≥1, the endemic equilibrium is globally asymptotically stable and epidemics occurs. Reported cases of 13646 HIV-1 positive were obtained in the year 2016 from Ministry of Health, Turkey (MOH). This data is used to present the numerical simulations, which supports the analytic result. \documentclass[12pt]{minimal}
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\begin{document}$$ R_{0} $$\end{document}R0 was found to be 1.98998, which is bigger than 1, this shows the threat posed by HIV in Turkey.
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da Silveira ID, Petersen MT, Sylvestre G, Garcia GA, David MR, Pavan MG, Maciel-de-Freitas R. Zika Virus Infection Produces a Reduction on Aedes aegypti Lifespan but No Effects on Mosquito Fecundity and Oviposition Success. Front Microbiol 2018; 9:3011. [PMID: 30619118 PMCID: PMC6305470 DOI: 10.3389/fmicb.2018.03011] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/21/2018] [Indexed: 11/13/2022] Open
Abstract
A Zika virus (ZIKV) pandemic started soon after the first autochthonous cases in Latin America. Although Aedes aegypti is pointed as the primary vector in Latin America, little is known about the fitness cost due to ZIKV infection. We investigated the effects of ZIKV infection on the life-history traits of Ae. aegypti females collected in three districts of Rio de Janeiro, Brazil (Barra, Deodoro, and Porto), equidistant ~25 km each other. Aedes aegypti mosquitoes were classified into infected (a single oral challenge with ZIKV) and superinfected (two ZIKV-infected blood meals spaced by 7 days each other). ZIKV infection reduced Ae. aegypti survival in two of the three populations tested, and superinfection produced a sharper increase in mortality in one of those populations. We hypothesized higher mortality with the presence of more ZIKV copies in Ae. aegypti females from Porto. The number of eggs laid per clutch was statistically similar between vector populations and infected and uninfected mosquitoes. Infection by ZIKV not affected female oviposition success. ZIKV infection impacted Ae. aegypti vectorial capacity by reducing its lifespan, although female fecundity remained unaltered. The outcome of these findings to disease transmission intensity still needs further evaluation.
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Affiliation(s)
- Isabella Dias da Silveira
- Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - Martha Thieme Petersen
- Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - Gabriel Sylvestre
- Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - Gabriela Azambuja Garcia
- Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - Mariana Rocha David
- Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | - Márcio Galvão Pavan
- Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.,Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Rafael Maciel-de-Freitas
- Laboratório de Mosquitos Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil.,Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Grunnill M. An exploration of the role of asymptomatic infections in the epidemiology of dengue viruses through susceptible, asymptomatic, infected and recovered (SAIR) models. J Theor Biol 2017; 439:195-204. [PMID: 29233775 DOI: 10.1016/j.jtbi.2017.12.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2017] [Revised: 11/21/2017] [Accepted: 12/08/2017] [Indexed: 02/03/2023]
Abstract
It is estimated that 20-97% of all dengue infections could be asymptomatic. I used SIR models to investigate the epidemiological role of such infections, by adding an asymptomatic class (SAIR models). Upon infection in one of the models, a human becomes either symptomatic or asymptomatic. In the other, a human becomes asymptomatic and may progress to being symptomatic. The robustness of results from these models is examined by incorporating the mosquito-vector into one of the models, followed by simulating epidemic dynamics stochastically. Results from the first two models were very similar, with epidemics typically lasting less than one year. When mosquitoes were explicitly modelled in a high-transmission setting, if the level or duration of infectivity from asymptomatic infections was high relative to symptomatic infections, dengue would become endemic. Under stochastic simulation this effect of asymptomatic infections leading to dengue persisting was no longer guaranteed. Longer durations in asymptomatic infections had a higher chance of causing dengue's persistence in stochastic simulation, indicating that this may be more of a key determinant for dengue's persistence to 10 years than the infectivity of such infections. Otherwise, the level and duration of infectivity from asymptomatic infections had similar effects on R0 and other epidemiological measures. With all models, outbreaks often led to a larger proportion of the population being immune than suggested by monitoring symptomatic dengue infections. This population would be at risk of developing severe dengue in a subsequent outbreak with a different dengue serotype, and would have to be determined via expansion factors.
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Affiliation(s)
- Martin Grunnill
- Center for Ecology and Conservation, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE, United Kingdom; USGS National Wildlife Health Center, 6006 Schroeder Road, Madison, WI 53711-6223, United States of America.
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11
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Sayan M, Hınçal E, Şanlıdağ T, Kaymakamzade B, Sa’ad FT, Baba IA. Dynamics of HIV/AIDS in Turkey from 1985 to 2016. ACTA ACUST UNITED AC 2017; 52:711-723. [PMID: 32214507 PMCID: PMC7088870 DOI: 10.1007/s11135-017-0648-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In this paper, we formulated a mathematical model that studies the dynamics of HIV/AIDS in Turkey from 1985 to 2016. We find two equilibrium points, disease free equilibrium and endemic equilibrium. Global stability analysis of the equilibria was conducted using Lyapunov function which depends on the basic reproduction ratio R0. If R0 < 1, the disease free equilibrium point is globally asymptotically stable, and if R0 ≥ 1 the endemic equilibrium point is globally asymptotically stable. We computed and predicted the basic reproduction ratios across all the years. It was found out that there were flaws in the exact values of R0 which is related to the poor registration system of HIV/AIDS in Turkey. Hence, there is need for the government to improve the system in order to cover the actual cases of the disease. The increase of the basic reproduction ratio over the years also shows the need for the relevant authorities to adopt appropriate control measures in combating the disease.
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Affiliation(s)
- Murat Sayan
- PCR Unit, Clinical Laboratory, Faculty of Medicine, Kocaeli University, Izmit, Kocaeli Turkey
| | - Evren Hınçal
- Department of Mathematics, Near East University, Nicosia, Northern Cyprus Turkey
| | - Tamer Şanlıdağ
- Department of Medical Microbiology, Faculty of Medicine, Celal Bayar University, Manisa, Turkey
- Research Center of Experimental Health Sciences, Near East University, Nicosia, Northern Cyprus Turkey
| | - Bilgen Kaymakamzade
- Department of Mathematics, Near East University, Nicosia, Northern Cyprus Turkey
| | - Farouk Tijjani Sa’ad
- Department of Mathematics, Near East University, Nicosia, Northern Cyprus Turkey
| | - Isa Abdullahi Baba
- Department of Mathematics, Near East University, Nicosia, Northern Cyprus Turkey
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Dengue burden in India: recent trends and importance of climatic parameters. Emerg Microbes Infect 2017; 6:e70. [PMID: 28790459 PMCID: PMC5583666 DOI: 10.1038/emi.2017.57] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 06/08/2017] [Indexed: 11/08/2022]
Abstract
For the past ten years, the number of dengue cases has gradually increased in India. Dengue is driven by complex interactions among host, vector and virus that are influenced by climatic factors. In the present study, we focused on the extrinsic incubation period (EIP) and its variability in different climatic zones of India. The EIP was calculated by using daily and monthly mean temperatures for the states of Punjab, Haryana, Gujarat, Rajasthan and Kerala. Among the studied states, a faster/low EIP in Kerala (8–15 days at 30.8 and 23.4 °C) and a generally slower/high EIP in Punjab (5.6–96.5 days at 35 and 0 °C) were simulated with daily temperatures. EIPs were calculated for different seasons, and Kerala showed the lowest EIP during the monsoon period. In addition, a significant association between dengue cases and precipitation was also observed. The results suggest that temperature is important in virus development in different climatic regions and may be useful in understanding spatio-temporal variations in dengue risk. Climate-based disease forecasting models in India should be refined and tailored for different climatic zones, instead of use of a standard model.
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Maxian O, Neufeld A, Talis EJ, Childs LM, Blackwood JC. Zika virus dynamics: When does sexual transmission matter? Epidemics 2017; 21:48-55. [PMID: 28688996 DOI: 10.1016/j.epidem.2017.06.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 05/10/2017] [Accepted: 06/26/2017] [Indexed: 12/13/2022] Open
Abstract
The Zika virus (ZIKV) has captured worldwide attention with the ongoing epidemic in South America and its link to severe birth defects, most notably microcephaly. ZIKV is spread to humans through a combination of vector and sexual transmission, but the relative contribution of these transmission routes to the overall epidemic remains largely unknown. Furthermore, a disparity in the reported number of infections between males and females has been observed. We develop a mathematical model that describes the transmission dynamics of ZIKV to determine the processes driving the observed epidemic patterns. Our model reveals a 4.8% contribution of sexual transmission to the basic reproductive number, R0. This contribution is too minor to independently sustain an outbreak but suggests that vector transmission is the main driver of the ongoing epidemic. We also find a minor, yet statistically significant, difference in the mean number of cases in males and females, both at the peak of the epidemic and at equilibrium. While this suggests an intrinsic disparity between males and females, the differences do not account for the vastly greater number of reported cases for females, indicative of a large reporting bias. In addition, we identify conditions under which sexual transmission may play a key role in sparking an epidemic, including temperate areas where ZIKV mosquito vectors are less prevalent.
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Affiliation(s)
- Ondrej Maxian
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, OH, USA
| | - Anna Neufeld
- Department of Mathematics and Statistics, Williams College, Williamstown, MA, USA
| | - Emma J Talis
- Department of Mathematics, Marist College, Poughkeepsie, NY, USA
| | - Lauren M Childs
- Department of Mathematics, Virginia Tech, Blacksburg, VA, USA
| | - Julie C Blackwood
- Department of Mathematics and Statistics, Williams College, Williamstown, MA, USA.
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Aldana Bermúdez E, Restrepo Triviño M, Muñoz Loaiza A. Ajuste de la fuerza de infección del dengue. Rev Salud Publica (Bogota) 2017; 19:194-198. [DOI: 10.15446/rsap.v19n2.37634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 12/16/2016] [Indexed: 11/09/2022] Open
Abstract
Objetivo Plantear un modelo matemático hospedero vector para el ajuste de la fuerza de infección del dengue en una población variable con crecimiento logístico y ciclo de vida del mosquito con tasa de ovoposición periódica, considerando inmunidad a un serotipo.Métodos El modelo matemático propuesto está representado por ocho ecuaciones diferenciales a las que se les calcula la fuerza de infección por el método de las redes libres de escala.Resultados Se presenta una simulación del modelo matemático resuelto mediante un algoritmo implementado en el software MATLAB con datos obtenidos de la literatura. En la simulación se puede observar el crecimiento de la fuerza de infección del dengue a través del tiempo, donde esta varía de acuerdo al cambio de algunos parámetros.Conclusiones La fuerza de la infección aumenta en el tiempo, es decir, la tasa de nuevos casos crece, mostrando la necesidad de prevención en las personas, mediante el uso de telas metálicas, mosquiteros, repelentes, ropa adecuada entre otras medidas; control químico como larvicidas y adulticidas contra el vector, como también la eliminación de criaderos que interrumpan su ciclo de vida
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Abstract
Background & Objectives Dengue is a climate-sensitive infectious disease. Climate-based dengue early warning may be a simple, low-cost, and effective tool for enhancing surveillance and control. Scientific studies on climate and dengue in local context form the basis for advancing the development of a climate-based early warning system. This study aims to review the current status of scientific studies in climate and dengue and the prospect or challenges of such research on a climate-based dengue early warning system in a dengue-endemic country, taking Malaysia as a case study. Method We reviewed the relationship between climate and dengue derived from statistical modeling, laboratory tests, and field studies. We searched electronic databases including PubMed, Scopus, EBSCO (MEDLINE), Web of Science, and the World Health Organization publications, and assessed climate factors and their influence on dengue cases, mosquitoes, and virus and recent development in the field of climate and dengue. Results & Discussion Few studies in Malaysia have emphasized the relationship between climate and dengue. Climatic factors such as temperature, rainfall, and humidity are associated with dengue; however, these relationships were not consistent. Climate change projections for Malaysia show a mounting risk for dengue in the future. Scientific studies on climate and dengue enhance dengue surveillance in the long run. Conclusion It is essential for institutions in Malaysia to promote research on climate and vector-borne diseases to advance the development of climate-based early warning systems. Together, effective strategies that improve existing research capacity, maximize the use of limited resources, and promote local-international partnership are crucial for sustaining research on climate and health.
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Affiliation(s)
- Yien Ling Hii
- Epidemiology and Global Health, Department of Public Health and Clinical Medicine, Umea University, Umea, Sweden.
| | - Rafdzah Ahmad Zaki
- Julius Centre University of Malaya, Department of Social and Preventive Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Nasrin Aghamohammadi
- Centre for Occupational and Environmental Health, Department of Social and Preventive Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Joacim Rocklöv
- Epidemiology and Global Health, Department of Public Health and Clinical Medicine, Umea University, Umea, Sweden
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16
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Padmanabha H, Correa F, Rubio C, Baeza A, Osorio S, Mendez J, Jones JH, Diuk-Wasser MA. Human Social Behavior and Demography Drive Patterns of Fine-Scale Dengue Transmission in Endemic Areas of Colombia. PLoS One 2015; 10:e0144451. [PMID: 26656072 PMCID: PMC4684369 DOI: 10.1371/journal.pone.0144451] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 11/18/2015] [Indexed: 01/09/2023] Open
Abstract
Dengue is known to transmit between humans and A. aegypti mosquitoes living in neighboring houses. Although transmission is thought to be highly heterogeneous in both space and time, little is known about the patterns and drivers of transmission in groups of houses in endemic settings. We carried out surveys of PCR positivity in children residing in 2-block patches of highly endemic cities of Colombia. We found high levels of heterogeneity in PCR positivity, varying from less than 30% in 8 of the 10 patches to 56 and 96%, with the latter patch containing 22 children simultaneously PCR positive (PCR22) for DEN2. We then used an agent-based model to assess the likely eco-epidemiological context of this observation. Our model, simulating daily dengue dynamics over a 20 year period in a single two block patch, suggests that the observed heterogeneity most likely derived from variation in the density of susceptible people. Two aspects of human adaptive behavior were critical to determining this density: external social relationships favoring viral introduction (by susceptible residents or infectious visitors) and immigration of households from non-endemic areas. External social relationships generating frequent viral introduction constituted a particularly strong constraint on susceptible densities, thereby limiting the potential for explosive outbreaks and dampening the impact of heightened vectorial capacity. Dengue transmission can be highly explosive locally, even in neighborhoods with significant immunity in the human population. Variation among neighborhoods in the density of local social networks and rural-to-urban migration is likely to produce significant fine-scale heterogeneity in dengue dynamics, constraining or amplifying the impacts of changes in mosquito populations and cross immunity between serotypes.
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Affiliation(s)
- Harish Padmanabha
- Centro de Investigaciones en el Desarrollo Humano (CIDHUM), Universidad del Norte, Km 5 Via Puerto Colombia, Puerto Colombia, Colombia
- National Socio-Environmental Synthesis Center (SESYNC), University of Maryland, 1 Park Place, Suite 300, Annapolis, Maryland, 21401, United States of America
- * E-mail:
| | - Fabio Correa
- Instituto Nacional de Salud de Colombia, Avenida/calle 26 No. 51–20 - Zona 6 CAN, Bogotá, D.C., Colombia
| | - Camilo Rubio
- Instituto Nacional de Salud de Colombia, Avenida/calle 26 No. 51–20 - Zona 6 CAN, Bogotá, D.C., Colombia
| | - Andres Baeza
- National Socio-Environmental Synthesis Center (SESYNC), University of Maryland, 1 Park Place, Suite 300, Annapolis, Maryland, 21401, United States of America
| | - Salua Osorio
- Instituto Nacional de Salud de Colombia, Avenida/calle 26 No. 51–20 - Zona 6 CAN, Bogotá, D.C., Colombia
| | - Jairo Mendez
- Instituto Nacional de Salud de Colombia, Avenida/calle 26 No. 51–20 - Zona 6 CAN, Bogotá, D.C., Colombia
| | - James Holland Jones
- Department of Anthropology/Woods Institute of the Environment, Stanford University, 450 Serra Mall, Building 50, Stanford, California, 94305–2034, United States of America
| | - Maria A Diuk-Wasser
- Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Ave, New York, New York, 10027, United States of America
- Department of Epidemiology of Microbial Diseases, Yale University, 60 College St, New Haven, Connecticut, 06520, United States of America
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17
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Rocha FP, Rodrigues HS, Monteiro MTT, Torres DF. Coexistence of two dengue virus serotypes and forecasting for Madeira Island. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.orhc.2015.07.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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18
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Costanzo KS, Schelble S, Jerz K, Keenan M. The effect of photoperiod on life history and blood-feeding activity in Aedes albopictus and Aedes aegypti (Diptera: Culicidae). JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2015; 40:164-171. [PMID: 26047197 DOI: 10.1111/jvec.12146] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 01/16/2015] [Indexed: 06/04/2023]
Abstract
Several studies have examined how climatic variables such as temperature and precipitation may affect life history traits in mosquitoes that are important to disease transmission. Despite its importance as a seasonal cue in nature, studies investigating the influence of photoperiod on such traits are relatively few. This study aims to investigate how photoperiod alters life history traits, survival, and blood-feeding activity in Aedes albopictus (Skuse) and Aedes aegypti (Linnaeus). We performed three experiments that tested the effects of day length on female survival, development time, adult size, fecundity, adult life span, and propensity to blood feed in Ae. albopictus and Ae. aegypti. Each experiment had three photoperiod treatments: 1) short-day (10L:14D), 2) control (12L:12D), and 3) long-day (14L:10D). Aedes albopictus adult females were consistently larger in size when reared in short-day conditions. Aedes aegypti adult females from short-day treatments lived longer and were more likely to take a blood meal compared to other treatments. We discuss how species-specific responses may reflect alternative strategies evolved to increase survival during unfavorable conditions. We review the potential impacts of these responses on seasonal transmission patterns, such as potentially increasing vectorial capacity of Ae. aegypti during periods of shorter day lengths.
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Affiliation(s)
- K S Costanzo
- Canisius College, Department of Biology, 2001 Main St., Buffalo, NY, U.S.A., 14208.
| | - S Schelble
- Canisius College, Department of Biology, 2001 Main St., Buffalo, NY, U.S.A., 14208
| | - K Jerz
- Canisius College, Department of Biology, 2001 Main St., Buffalo, NY, U.S.A., 14208
| | - M Keenan
- Canisius College, Department of Biology, 2001 Main St., Buffalo, NY, U.S.A., 14208
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20
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Alto BW, Richards SL, Anderson SL, Lord CC. Survival of West Nile virus-challenged Southern house mosquitoes, Culex pipiens quinquefasciatus, in relation to environmental temperatures. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2014; 39:123-33. [PMID: 24820564 PMCID: PMC4874492 DOI: 10.1111/j.1948-7134.2014.12078.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 02/17/2014] [Indexed: 05/25/2023]
Abstract
We investigated the effect of West Nile virus (WNV) infection on survival in two colonies of Culex pipiens quinquefasciatus Say (Diptera: Culicidae) originating from Vero Beach and Gainesville, FL. Mosquitoes were fed West Nile virus-infected blood and checked daily for survival. Exposure to WNV decreased survival among Cx. p. quinquefasciatus from Gainesville relative to unexposed individuals at 31° C. In contrast, exposure to WNV enhanced survival among Cx. p. quinquefasciatus from Vero Beach relative to unexposed individuals at 27° C. These results may suggest that exposure to WNV and associated infection could increase or decrease components of fitness, dependent on environmental temperature and intraspecific variation in Cx. p. quinquefasciatus. The relationship between lifespan (time of death in days) and WNV titer differed in the colonies at 31° C and 27° C, suggesting that intraspecific species variation in response to temperature impacts interactions with WNV. While further work is needed to determine if similar effects occur under field conditions, this suggests intraspecific variation in vector competence for WNV and adult survival of Cx. p. quinquefasciatus, both aspects of vectorial capacity.
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Affiliation(s)
- Barry W Alto
- Florida Medical Entomology Laboratory, University of Florida, 200 9th St. S.E. Vero Beach, FL 32962, U.S.A..
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21
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A stuctured discrete model for dengue fever infections and the determination of R0 from age-stratified serological data. Bull Math Biol 2014; 76:1288-305. [PMID: 24771274 DOI: 10.1007/s11538-014-9956-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 03/27/2014] [Indexed: 10/25/2022]
Abstract
A time discrete age-structured model for modeling the spread of Dengue fever is built. The demographic dynamics is introduced trough the Leslie model. The basic reproductive number is introduced, and an approximation for it is built. The final age distributions for the susceptibles, infected and removed are obtained, and we show how they can be used to produce an actual estimate for R0 from stratified serological data. An application is made using data from Recife, Brazil, and explicit estimates for R0 are given.
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22
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LORD CC, ALTO BW, ANDERSON SL, CONNELLY CR, DAY JF, RICHARDS SL, SMARTT CT, TABACHNICK WJ. Can Horton hear the whos? The importance of scale in mosquito-borne disease. JOURNAL OF MEDICAL ENTOMOLOGY 2014; 51:297-313. [PMID: 24724278 PMCID: PMC5027650 DOI: 10.1603/me11168] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The epidemiology of vector-borne pathogens is determined by mechanisms and interactions at different scales of biological organization, from individual-level cellular processes to community interactions between species and with the environment. Most research, however, focuses on one scale or level with little integration between scales or levels within scales. Understanding the interactions between levels and how they influence our perception of vector-borne pathogens is critical. Here two examples of biological scales (pathogen transmission and mosquito mortality) are presented to illustrate some of the issues of scale and to explore how processes on different levels may interact to influence mosquito-borne pathogen transmission cycles. Individual variation in survival, vector competence, and other traits affect population abundance, transmission potential, and community structure. Community structure affects interactions between individuals such as competition and predation, and thus influences the individual-level dynamics and transmission potential. Modeling is a valuable tool to assess interactions between scales and how processes at different levels can affect transmission dynamics. We expand an existing model to illustrate the types of studies needed, showing that individual-level variation in viral dose acquired or needed for infection can influence the number of infectious vectors. It is critical that interactions within and among biological scales and levels of biological organization are understood for greater understanding of pathogen transmission with the ultimate goal of improving control of vector-borne pathogens.
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Affiliation(s)
- C. C. LORD
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - B. W. ALTO
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - S. L. ANDERSON
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - C. R. CONNELLY
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - J. F. DAY
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - S. L. RICHARDS
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - C. T. SMARTT
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
| | - W. J. TABACHNICK
- Florida Medical Entomology Laboratory, Department of Entomology and
Nematology, University of Florida – IFAS, 200 9th St. SE, Vero Beach, FL
32962
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Lana RM, Carneiro TGS, Honório NA, Codeço CT. Seasonal and nonseasonal dynamics of Aedes aegypti in Rio de Janeiro, Brazil: fitting mathematical models to trap data. Acta Trop 2014; 129:25-32. [PMID: 23933186 DOI: 10.1016/j.actatropica.2013.07.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Revised: 05/31/2013] [Accepted: 07/22/2013] [Indexed: 11/15/2022]
Abstract
Mathematical models suggest that seasonal transmission and temporary cross-immunity between serotypes can determine the characteristic multi-year dynamics of dengue fever. Seasonal transmission is attributed to the effect of climate on mosquito abundance and within host virus dynamics. In this study, we validate a set of temperature and density dependent entomological models that are built-in components of most dengue models by fitting them to time series of ovitrap data from three distinct neighborhoods in Rio de Janeiro, Brazil. The results indicate that neighborhoods differ in the strength of the seasonal component and that commonly used models tend to assume more seasonal structure than found in data. Future dengue models should investigate the impact of heterogeneous levels of seasonality on dengue dynamics as it may affect virus maintenance from year to year, as well as the risk of disease outbreaks.
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Affiliation(s)
- Raquel M Lana
- Laboratório para Modelagem e Simulação de Sistemas Terrestres, Depto. de Ciências de Computação, ICEB/UFOP, 35400-000 Ouro Preto, MG, Brazil; Programa de Computação Científica, Fiocruz, Manguinhos, 21045-900 Rio de Janeiro, RJ, Brazil.
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24
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Chowell G, Fuentes R, Olea A, Aguilera X, Nesse H, Hyman JM. The basic reproduction number R0 and effectiveness of reactive interventions during dengue epidemics: the 2002 dengue outbreak in Easter Island, Chile. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2013; 10:1455-74. [PMID: 24245625 PMCID: PMC4397933 DOI: 10.3934/mbe.2013.10.1455] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We use a stochastic simulation model to explore the effect of reactive intervention strategies during the 2002 dengue outbreak in the small population of Easter Island, Chile. We quantified the effect of interventions on the transmission dynamics and epidemic size as a function of the simulated control intensity levels and the timing of initiation of control interventions. Because no dengue outbreaks had been reported prior to 2002 in Easter Island, the 2002 epidemic provided a unique opportunity to estimate the basic reproduction number R0 during the initial epidemic phase, prior to the start of control interventions. We estimated R0 at 27.2 (95%CI: 14.8, 49.3). We found that the final epidemic size is highly sensitive to the timing of start of interventions. However, even when the control interventions start several weeks after the epidemic onset, reactive intervention efforts can have a significant impact on the final epidemic size. Our results indicate that the rapid implementation of control interventions can have a significant effect in reducing the epidemic size of dengue epidemics.
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Affiliation(s)
- G. Chowell
- Mathematical and Computational Modeling Sciences Center, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA, and, Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA
| | - R. Fuentes
- Department of Epidemiology, Ministerio de Salud, Santiago, Chile
| | - A. Olea
- Universidad del Desarrollo, Santiago, Chile
| | | | - H. Nesse
- School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287, USA
| | - J. M. Hyman
- Tulane University, New Orleans, LA, 70118, USA
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Abstract
Epidemiological models may give some basic guidelines for public health practitioners, allowing the analysis of issues that can influence the strategies to prevent and fight a disease. To be used in decision making, however, a mathematical model must be carefully parameterized and validated with epidemiological and entomological data. Here an SIR (S for susceptible, I for infectious, and R for recovered individuals) and ASI (A for the aquatic phase of the mosquito, S for susceptible, and I for infectious mosquitoes) epidemiological model describing a dengue disease is presented, as well as the associated basic reproduction number. A sensitivity analysis of the epidemiological model is performed in order to determine the relative importance of the model parameters to the disease transmission.
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26
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Tjaden NB, Thomas SM, Fischer D, Beierkuhnlein C. Extrinsic Incubation Period of Dengue: Knowledge, Backlog, and Applications of Temperature Dependence. PLoS Negl Trop Dis 2013; 7:e2207. [PMID: 23826399 PMCID: PMC3694834 DOI: 10.1371/journal.pntd.0002207] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
| | | | - Dominik Fischer
- Department of Biogeography, University of Bayreuth, Bayreuth, Germany
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Hsieh YH, de Arazoza H, Lounes R. Temporal trends and regional variability of 2001-2002 multiwave DENV-3 epidemic in Havana City: did Hurricane Michelle contribute to its severity? Trop Med Int Health 2013; 18:830-8. [PMID: 23590206 DOI: 10.1111/tmi.12105] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To investigate the temporal and regional variability of the 2001-2002 dengue outbreak in Havana City where 12 889 cases, mostly of DENV-3 type, were reported over a period of 7 months. METHODS A simple mathematical model, the Richards model, was used to fit the weekly reported dengue case data by municipality, in order to quantify the transmissibility and temporal changes in the epidemic in each municipality via the basic reproduction number R0 . RESULTS Model fits indicate either a 2-wave or 3-wave outbreak in all municipalities. Estimates for R0 varied greatly, from 1.97 (95% CI: 1.94, 2.01), for Arroyo Naranjo, to 61.06 (60.44, 61.68), for Boyeros, most likely due to heterogeneity in community structure, geographical locations and social networking. CONCLUSIONS Our results illustrate the potential impact of climatological events on disease spread, further highlighting the need to be well prepared for potentially worsening disease spread in the aftermath of natural disasters such as hurricanes/typhoons.
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Affiliation(s)
- Ying-Hen Hsieh
- Department of Public Health and Center for Infectious Disease Education and Research, China Medical University, Taichung, Taiwan.
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28
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Multiscale analysis for a vector-borne epidemic model. J Math Biol 2013; 68:1269-93. [DOI: 10.1007/s00285-013-0666-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 02/14/2013] [Indexed: 11/30/2022]
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29
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Sylvestre G, Gandini M, Maciel-de-Freitas R. Age-dependent effects of oral infection with dengue virus on Aedes aegypti (Diptera: Culicidae) feeding behavior, survival, oviposition success and fecundity. PLoS One 2013; 8:e59933. [PMID: 23555838 PMCID: PMC3612067 DOI: 10.1371/journal.pone.0059933] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 02/20/2013] [Indexed: 11/18/2022] Open
Abstract
Background Aedes aegypti is the main vector of dengue, a disease that is increasing its geographical range as well as incidence rates. Despite its public health importance, the effect of dengue virus (DENV) on some mosquito traits remains unknown. Here, we investigated the impact of DENV-2 infection on the feeding behavior, survival, oviposition success and fecundity of Ae. aegypti females. Methods/Principal Findings After orally-challenging Ae. aegypti females with a DENV-2 strain using a membrane feeder, we monitored the feeding behavior, survival, oviposition success and fecundity throughout the mosquito lifespan. We observed an age-dependent cost of DENV infection on mosquito feeding behavior and fecundity. Infected individuals took more time to ingest blood from anesthetized mice in the 2nd and 3rd weeks post-infection, and also longer overall blood-feeding times in the 3rd week post-infection, when females were around 20 days old. Often, infected Ae. aegypti females did not lay eggs and when they were laid, smaller number of eggs were laid compared to uninfected controls. A reduction in the number of eggs laid per female was evident starting on the 3rd week post-infection. DENV-2 negatively affected mosquito lifespan, since overall the longevity of infected females was halved compared to that of the uninfected control group. Conclusions The DENV-2 strain tested significantly affected Ae. aegypti traits directly correlated with vectorial capacity or mosquito population density, such as feeding behavior, survival, fecundity and oviposition success. Infected mosquitoes spent more time ingesting blood, had reduced lifespan, laid eggs less frequently, and when they did lay eggs, the clutches were smaller than uninfected mosquitoes.
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Affiliation(s)
- Gabriel Sylvestre
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz - Fiocruz, Rio de Janeiro, Brazil
| | - Mariana Gandini
- Laboratório de Imunologia Viral, Instituto Oswaldo Cruz - Fiocruz, Fiocruz, Rio de Janeiro, Brazil
| | - Rafael Maciel-de-Freitas
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz - Fiocruz, Rio de Janeiro, Brazil
- * E-mail:
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Simulation of the probable vector density that caused the Nagasaki dengue outbreak vectored by Aedes albopictus in 1942. Epidemiol Infect 2013; 141:2612-22. [PMID: 23481094 PMCID: PMC3821399 DOI: 10.1017/s0950268813000447] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Japan experienced dengue outbreaks vectored by Aedes albopictus during the Second World War. The probable vector density that caused the largest dengue outbreak in Nagasaki in 1942 was estimated using a mathematical simulation model. The estimated vector density was 15·0–558·0 per person when various assumptions of uncertain parameters were applied, such as proportion of symptomatic cases, vector mortality, and human biting rate of A. albopictus. When the most favourable disease spread conditions, such as a combination of the exclusive human biting rate and the longest vector survival were assumed, the vector density was 15–25 mosquitoes per person. Unusually high vector density due to wartime practices, and the traditional Japanese lifestyle were presumably responsible for the earlier dengue outbreak. If an outbreak occurs in present-day Japan, it is unlikely to spread as much as the previous one, as environmental conditions and human behaviour have changed in a protective manner.
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Predictive Dynamics: Modeling for Virological Surveillance and Clinical Management of Dengue. DYNAMIC MODELS OF INFECTIOUS DISEASES 2013. [PMCID: PMC7121019 DOI: 10.1007/978-1-4614-3961-5_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dengue fever is a flu-like illness spread by the bite of an infected mosquito and is fast emerging as a major public health concern. Timely and cost-effective diagnosis would reduce the mortality rates besides providing better grounds for clinical management and disease surveillance. Identifying the clinical features for early diagnosis of dengue would be useful in reducing the virus transmission in a community. In addition to the clinical features, obtaining the influential laboratory attributes and their range would aid in quick identification of disease severity in the suspected individuals. In this chapter a new alternating decision tree methodology which generates more accurate and simplified decision tree structures with simplified classification rules is discussed. This approach helps one to obtain the influential clinical and laboratory features which would aid in identifying the suspected dengue individuals and assess the severity of infection in them.
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Oki M, Yamamoto T. Climate change, population immunity, and hyperendemicity in the transmission threshold of dengue. PLoS One 2012; 7:e48258. [PMID: 23144746 PMCID: PMC3483158 DOI: 10.1371/journal.pone.0048258] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 09/21/2012] [Indexed: 11/24/2022] Open
Abstract
Background It has been suggested that the probability of dengue epidemics could increase because of climate change. The probability of epidemics is most commonly evaluated by the basic reproductive number (R0), and in mosquito-borne diseases, mosquito density (the number of female mosquitoes per person [MPP]) is the critical determinant of the R0 value. In dengue-endemic areas, 4 different serotypes of dengue virus coexist–a state known as hyperendemicity–and a certain proportion of the population is immune to one or more of these serotypes. Nevertheless, these factors are not included in the calculation of R0. We aimed to investigate the effects of temperature change, population immunity, and hyperendemicity on the threshold MPP that triggers an epidemic. Methods and Findings We designed a mathematical model of dengue transmission dynamics. An epidemic was defined as a 10% increase in seroprevalence in a year, and the MPP that triggered an epidemic was defined as the threshold MPP. Simulations were conducted in Singapore based on the recorded temperatures from 1980 to 2009 The threshold MPP was estimated with the effect of (1) temperature only; (2) temperature and fluctuation of population immunity; and (3) temperature, fluctuation of immunity, and hyperendemicity. When only the effect of temperature was considered, the threshold MPP was estimated to be 0.53 in the 1980s and 0.46 in the 2000s, a decrease of 13.2%. When the fluctuation of population immunity and hyperendemicity were considered in the model, the threshold MPP decreased by 38.7%, from 0.93 to 0.57, from the 1980s to the 2000s. Conclusions The threshold MPP was underestimated if population immunity was not considered and overestimated if hyperendemicity was not included in the simulations. In addition to temperature, these factors are particularly important when quantifying the threshold MPP for the purpose of setting goals for vector control in dengue-endemic areas.
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Affiliation(s)
- Mika Oki
- Department of International Health, Institute of Tropical Medicine, The Global Center of Excellence, Nagasaki University, Nagasaki, Japan.
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Event history analysis of dengue fever epidemic and inter-epidemic spells in Barbados, Brazil, and Thailand. Int J Infect Dis 2012; 16:e793-8. [PMID: 22878174 DOI: 10.1016/j.ijid.2012.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2012] [Accepted: 07/02/2012] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE This study investigated meteorological and demographic factors affecting the length of dengue fever epidemics and the length of time between epidemics in Barbados, Brazil, and Thailand. METHODS Region-specific meteorological and demographic data were collected for 104 sites from public sources. Fixed effects piecewise logistic event history analysis was used to quantify the effects of time-varying covariates on the duration of inter-epidemic spells and for the duration of epidemics. RESULTS Mean monthly temperature was the most important factor affecting the duration of both inter-epidemic spells (β=0.543; confidence interval (CI) 0.4954, 0.5906) and epidemic spells (β=-0.648; CI -0.7553, -0.5405). Drought conditions increased the time between epidemics. Increased temperature hastened the onset of an epidemic, and during an epidemic, higher mean temperature increased the duration of the epidemic. CONCLUSIONS By using a duration analysis, this study offers a novel approach for investigating the dynamics of dengue fever epidemiology. Furthermore, these results offer new insights into prior findings of a correlation between temperature and the geographic range and vector efficiency of dengue fever.
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Emergence and prevalence of human vector-borne diseases in sink vector populations. PLoS One 2012; 7:e36858. [PMID: 22629337 PMCID: PMC3356347 DOI: 10.1371/journal.pone.0036858] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Accepted: 04/16/2012] [Indexed: 01/04/2023] Open
Abstract
Vector-borne diseases represent a major public health concern in most tropical and subtropical areas, and an emerging threat for more developed countries. Our understanding of the ecology, evolution and control of these diseases relies predominantly on theory and data on pathogen transmission in large self-sustaining ‘source’ populations of vectors representative of highly endemic areas. However, there are numerous places where environmental conditions are less favourable to vector populations, but where immigration allows them to persist. We built an epidemiological model to investigate the dynamics of six major human vector borne-diseases in such non self-sustaining ‘sink’ vector populations. The model was parameterized through a review of the literature, and we performed extensive sensitivity analysis to look at the emergence and prevalence of the pathogen that could be encountered in these populations. Despite the low vector abundance in typical sink populations, all six human diseases were able to spread in 15–55% of cases after accidental introduction. The rate of spread was much more strongly influenced by vector longevity, immigration and feeding rates, than by transmission and virulence of the pathogen. Prevalence in humans remained lower than 5% for dengue, leishmaniasis and Japanese encephalitis, but substantially higher for diseases with longer duration of infection; malaria and the American and African trypanosomiasis. Vector-related parameters were again the key factors, although their influence was lower than on pathogen emergence. Our results emphasize the need for ecology and evolution to be thought in the context of metapopulations made of a mosaic of sink and source habitats, and to design vector control program not only targeting areas of high vector density, but working at a larger spatial scale.
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Johansson MA, Hombach J, Cummings DA. Models of the impact of dengue vaccines: a review of current research and potential approaches. Vaccine 2011; 29:5860-8. [PMID: 21699949 PMCID: PMC4327892 DOI: 10.1016/j.vaccine.2011.06.042] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 06/10/2011] [Accepted: 06/14/2011] [Indexed: 11/27/2022]
Abstract
Vaccination reduces transmission of pathogens directly, by preventing individual infections, and indirectly, by reducing the probability of contact between infected individuals and susceptible ones. The potential combined impact of future dengue vaccines can be estimated using mathematical models of transmission. However, there is considerable uncertainty in the structure of models that accurately represent dengue transmission dynamics. Here, we review models that could be used to assess the impact of future dengue immunization programmes. We also review approaches that have been used to validate and parameterize models. A key parameter of all approaches is the basic reproduction number, R(0), which can be used to determine the critical vaccination fraction to eliminate transmission. We review several methods that have been used to estimate this quantity. Finally, we discuss the characteristics of dengue vaccines that must be estimated to accurately assess their potential impact on dengue virus transmission.
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Affiliation(s)
- Michael A. Johansson
- Division of Vector-Borne Diseases, U.S. Centers for Disease Control, San Juan, PR 00920
| | - Joachim Hombach
- Initiative for Vaccine Research, World Health Organization, Geneva, Switzerland
| | - Derek A.T. Cummings
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205
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Maciel-de-Freitas R, Koella JC, Lourenço-de-Oliveira R. Lower survival rate, longevity and fecundity of Aedes aegypti (Diptera: Culicidae) females orally challenged with dengue virus serotype 2. Trans R Soc Trop Med Hyg 2011; 105:452-8. [PMID: 21700303 DOI: 10.1016/j.trstmh.2011.05.006] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2010] [Revised: 05/12/2011] [Accepted: 05/12/2011] [Indexed: 11/25/2022] Open
Abstract
As the pathogenic effects of a parasite on its hosts can strongly influence its epidemiology, we compared the life-histories of dengue virus serotype 2 (DENV-2)-infected and uninfected Aedes aegypti females. Unexposed mosquitoes lived longer than exposed ones, but those infected lived longer than exposed but negative (as assayed by Real-Time quantitative Reverse Transcription PCR [qRT-PCR]) mosquitoes. Infected mosquitoes from a long-established laboratory colony presented more viral RNA copies at death than those from the F1-generation of a field population from Rio de Janeiro. The mortality of infected colony-mosquitoes was independent of the number of viral RNA copies at death, whereas in the field population, longevity decreased with the number of viral RNA copies, suggesting that F1 of field mosquitoes are less tolerant to infection than the laboratory-colony. Infected females had a lower fecundity than controls. F1 of field mosquitoes were more likely to lay eggs than the colony; egg-laying success was strongly affected by mosquito age for both mosquito populations: from 49.28 in the first clutch to 20.7 in the fifth. Overall, DENV-2 reduced Aedes aegypti survival and fecundity, clearly affecting vectorial capacity and consequently transmission intensity.
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Affiliation(s)
- R Maciel-de-Freitas
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz, Fiocruz, Avenida Brasil 4365, 21040-360, Rio de Janeiro, RJ, Brazil.
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Alto BW. Interspecific larval competition between invasive Aedes japonicus and native Aedes triseriatus (Diptera: Culicidae) and adult longevity. JOURNAL OF MEDICAL ENTOMOLOGY 2011; 48:232-242. [PMID: 21485358 DOI: 10.1603/me09252] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The Asian rock pool mosquito Aedes japonicus (Theobald) inhabits natural and artificial container habitats, some of which are occupied by the native treehole mosquitoAedes triseriatus (Say), a vector of LaCrosse encephalitis virus. A laboratory experiment was used to evaluate the effects of nutrient limitation and interspecific interactions between these species. The goal was to address two related hypotheses. First, interspecific interactions between these species show competitive asymmetry with the invasive mosquito Ae. japonicus being favored over Ae. triseriatus. Second, competitive stress at the larval stage alters adult longevity. There was minimal evidence for competitive asymmetry between these two species. Mosquito and population performance showed clear negative density-dependent effects with similar effects of intra- and interspecific interactions. Only Ae. japonicus development time showed competitive asymmetry over Ae. triseriatus, providing weak support for the first hypothesis. For both species, competition resulted in lower adult longevity compared with low competition, providing support for the second hypothesis. These results suggest both species are similarly affected by intra- and interspecific competition and underscore the importance of the effects of larval competition that continue into adulthood and alter parameters important to transmission of vector-borne diseases.
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Affiliation(s)
- Barry W Alto
- University of Illinois, Illinois Natural History Survey, 1816 S. Oak Street, Champaign, IL 61820, USA.
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de Castro Medeiros LC, Castilho CAR, Braga C, de Souza WV, Regis L, Monteiro AMV. Modeling the dynamic transmission of dengue fever: investigating disease persistence. PLoS Negl Trop Dis 2011; 5:e942. [PMID: 21264356 PMCID: PMC3019115 DOI: 10.1371/journal.pntd.0000942] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Accepted: 12/09/2010] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Dengue is a disease of great complexity, due to interactions between humans, mosquitoes and various virus serotypes as well as efficient vector survival strategies. Thus, understanding the factors influencing the persistence of the disease has been a challenge for scientists and policy makers. The aim of this study is to investigate the influence of various factors related to humans and vectors in the maintenance of viral transmission during extended periods. METHODOLOGY/PRINCIPAL FINDINGS We developed a stochastic cellular automata model to simulate the spread of dengue fever in a dense community. Each cell can correspond to a built area, and human and mosquito populations are individually monitored during the simulations. Human mobility and renewal, as well as vector infestation, are taken into consideration. To investigate the factors influencing the maintenance of viral circulation, two sets of simulations were performed: (1(st)) varying human renewal rates and human population sizes and (2(nd)) varying the house index (fraction of infested buildings) and vector per human ratio. We found that viral transmission is inhibited with the combination of small human populations with low renewal rates. It is also shown that maintenance of viral circulation for extended periods is possible at low values of house index. Based on the results of the model and on a study conducted in the city of Recife, Brazil, which associates vector infestation with Aedes aegytpi egg counts, we question the current methodology used in calculating the house index, based on larval survey. CONCLUSIONS/SIGNIFICANCE This study contributed to a better understanding of the dynamics of dengue subsistence. Using basic concepts of metapopulations, we concluded that low infestation rates in a few neighborhoods ensure the persistence of dengue in large cities and suggested that better strategies should be implemented to obtain measures of house index values, in order to improve the dengue monitoring and control system.
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Luz PM, Struchiner CJ, Galvani AP. Modeling transmission dynamics and control of vector-borne neglected tropical diseases. PLoS Negl Trop Dis 2010; 4:e761. [PMID: 21049062 PMCID: PMC2964290 DOI: 10.1371/journal.pntd.0000761] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Neglected tropical diseases affect more than one billion people worldwide. The populations most impacted by such diseases are typically the most resource-limited. Mathematical modeling of disease transmission and cost-effectiveness analyses can play a central role in maximizing the utility of limited resources for neglected tropical diseases. We review the contributions that mathematical modeling has made to optimizing intervention strategies of vector-borne neglected diseases. We propose directions forward in the modeling of these diseases, including integrating new knowledge of vector and pathogen ecology, incorporating evolutionary responses to interventions, and expanding the scope of sensitivity analysis in order to achieve robust results.
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Affiliation(s)
- Paula M Luz
- School of Public Health, Yale University, New Haven, Connecticut, USA.
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Honório NA, Codeço CT, Alves FC, Magalhães MAFM, Lourenço-De-Oliveira R. Temporal distribution of Aedes aegypti in different districts of Rio de Janeiro, Brazil, measured by two types of traps. JOURNAL OF MEDICAL ENTOMOLOGY 2009; 46:1001-14. [PMID: 19769029 DOI: 10.1603/033.046.0505] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Dengue dynamics in Rio de Janeiro, Brazil, as in many dengue-endemic regions of the world, is seasonal, with peaks during the wet-hot months. This temporal pattern is generally attributed to the dynamics of its mosquito vector Aedes aegypti (L.). The objectives of this study were to characterize the temporal pattern of Ae. aegypti population dynamics in three neighborhoods of Rio de Janeiro and its association with local meteorological variables; and to compare positivity and density indices obtained with ovitraps and MosquiTraps. The three neighborhoods are distinct in vegetation coverage, sanitation, water supply, and urbanization. Mosquito sampling was carried out weekly, from September 2006 to March 2008, a period during which large dengue epidemics occurred in the city. Our results show peaks of oviposition in early summer 2007 and late summer 2008, detected by both traps. The ovitrap provided a more sensitive index than MosquiTrap. The MosquiTrap detection threshold showed high variation among areas, corresponding to a mean egg density of approximately 25-52 eggs per ovitrap. Both temperature and rainfall were significantly related to Ae. aegypti indices at a short (1 wk) time lag. Our results suggest that mean weekly temperature above 22-24 degrees C is strongly associated with high Ae. aegypti abundance and consequently with an increased risk of dengue transmission. Understanding the effects of meteorological variables on Ae. aegypti population dynamics will help to target control measures at the times when vector populations are greatest, contributing to the development of climate-based control and surveillance measures for dengue fever in a hyperendemic area.
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Affiliation(s)
- N A Honório
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz-Fiocruz, Av. Brasil 4365, Manguinhos, Rio de Janeiro, CEP 21045-900, Brasil.
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Adams B, Kapan DD. Man bites mosquito: understanding the contribution of human movement to vector-borne disease dynamics. PLoS One 2009; 4:e6763. [PMID: 19707544 PMCID: PMC2727792 DOI: 10.1371/journal.pone.0006763] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Accepted: 07/27/2009] [Indexed: 11/29/2022] Open
Abstract
In metropolitan areas people travel frequently and extensively but often in highly structured commuting patterns. We investigate the role of this type of human movement in the epidemiology of vector-borne pathogens such as dengue. Analysis is based on a metapopulation model where mobile humans connect static mosquito subpopulations. We find that, due to frequency dependent biting, infection incidence in the human and mosquito populations is almost independent of the duration of contact. If the mosquito population is not uniformly distributed between patches the transmission potential of the pathogen at the metapopulation level, as summarized by the basic reproductive number, is determined by the size of the largest subpopulation and reduced by stronger connectivity. Global extinction of the pathogen is less likely when increased human movement enhances the rescue effect but, in contrast to classical theory, it is not minimized at an intermediate level of connectivity. We conclude that hubs and reservoirs of infection can be places people visit frequently but briefly and the relative importance of human and mosquito populations in maintaining the pathogen depends on the distribution of the mosquito population and the variability in human travel patterns. These results offer an insight in to the paradoxical observation of resurgent urban vector-borne disease despite increased investment in vector control and suggest that successful public health intervention may require a dual approach. Prospective studies can be used to identify areas with large mosquito populations that are also visited by a large fraction of the human population. Retrospective studies can be used to map recent movements of infected people, pinpointing the mosquito subpopulation from which they acquired the infection and others to which they may have transmitted it.
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Affiliation(s)
- Ben Adams
- Department of Biology, Kyushu University, Fukuoka, Japan.
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Abstract
SUMMARYA previous mathematical model explaining dengue in Singapore predicted a reasonable outbreak of about 6500 cases for 2006 and a very mild outbreak with about 2000 cases for 2007. However, only 3051 cases were reported in 2006 while more than 7800 were reported in the first 44 weeks of 2007. We hypothesized that the combination of haze with other local sources of particulate matter had a significant impact on mosquito life expectancy, significantly increasing their mortality rate. To test the hypothesis a mathematical model based on the reproduction number of dengue fever and aimed at comparing the impact of several possible alternative control strategies was proposed. This model also aimed at contributing to the understanding of the causes of dengue resurgence in Singapore in the last decade. The model's simulation demonstrated that an increase in mosquito mortality in 2006 and either a reduction in mortality or an increase in the carrying capacity of mosquitoes in 2007 explained the patterned observed in Singapore. Based on the model's simulation we concluded that the fewer than expected number of dengue cases in Singapore in 2006 was caused by an increase in mosquito mortality due to the disproportionate haze affecting the country that year and that particularly favourable environmental conditions in 2007 propitiated mosquitoes with a lower mortality rate, which explains the greater than expected number of dengue cases in 2007. Whether our hypothesis is plausible or not should be debated further.
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Hsieh YH, Chen CWS. Turning points, reproduction number, and impact of climatological events for multi-wave dengue outbreaks. Trop Med Int Health 2009; 14:628-38. [PMID: 19392743 DOI: 10.1111/j.1365-3156.2009.02277.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVES To study climatological and public health events which might have affected the 2007 two-wave dengue outbreak in Taiwan, an island with both tropical and subtropical regions, where the 2007 dengue incidence exceeded the combined total of the previous four years. METHODS A multi-phase Richards model was fitted to weekly cumulative dengue data to pinpoint the turning points of the outbreak. We obtained the 'initial' reproduction numbers for the two waves of the outbreak. By means of correlation analysis we explored the possible impact of climatological events on the occurrence of turning points. RESULTS Three turning points occurred around early August, late August/early September, and late October/early November. The 'initial' reproduction number for the first wave was R(i) = 4.67 (95% CI: 0*-10.92), where 0* = max{0, lower bound}, and R(i) = 3.93 (95% CI: 1.74-6.13) for the second wave. The highest correlation was between dengue incidence and two climatological variables: maximum temperature at a lag of 5 weeks (r = 0.66 and 0.71) and total precipitation at a lag of seven weeks (r = 0.53). Conclusions The first two turning points were partially attributable to two typhoons around early to mid-August that brought a sharp drop in temperature and substantial rainfall. The drop in temperature first drove the dengue incidence down, then the rainfall drove it up at the beginning of fall. In recent years, Taiwan has witnessed increasingly frequent large summer dengue outbreaks that persisted into early winter, perhaps due to warmer autumns. This highlights the possible impact of global warming on the spread of infectious diseases.
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Affiliation(s)
- Y-H Hsieh
- Department of Public health and Institute of Biostatistics, China Medical University, Taichung, Taiwan.
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Reiskind MH, Lounibos LP. Effects of intraspecific larval competition on adult longevity in the mosquitoes Aedes aegypti and Aedes albopictus. MEDICAL AND VETERINARY ENTOMOLOGY 2009; 23:62-8. [PMID: 19239615 PMCID: PMC2651082 DOI: 10.1111/j.1365-2915.2008.00782.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Larval competition is common in container-breeding mosquitoes. The impact of competition on larval growth has been thoroughly examined and findings that larval competition can lead to density-dependent effects on adult body size have been documented. The effects of larval competition on adult longevity have been less well explored. The effects of intraspecific larval densities on the longevity of adults maintained under relatively harsh environmental conditions were tested in the laboratory by measuring the longevity of adult Aedes aegypti (L.) and Aedes albopictus (Skuse) (Diptera: Culicidae) that had been reared under a range of larval densities and subsequently maintained in high- or low-humidity regimes (85% or 35% relative humidity [RH], respectively) as adults. We found significant negative effects of competition on adult longevity in Ae. aegypti, but not in Ae. albopictus. Multivariate analysis of variance suggested that the negative effect of the larval environment on the longevity of Ae. aegypti adults was most strongly associated with increased development time and decreased wing length as adults. Understanding how larval competition affects adult longevity under a range of environmental conditions is important in establishing the relationship between models of mosquito population regulation and epidemiological models of vector-borne disease transmission.
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Affiliation(s)
- M H Reiskind
- Florida Medical Entomology Laboratory, Department of Entomology and Nematology, University of Florida, Vero Beach, Florida, USA.
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Chaib E, Massad E. The potential impact of using donations after cardiac death on the liver transplantation program and waiting list in the state of Sao Paulo, Brazil. Liver Transpl 2008; 14:1732-6. [PMID: 19025927 DOI: 10.1002/lt.21611] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Liver transplantation was first performed at the University of Sao Paulo School of Medicine in 1968. Since then, the patient waiting list for liver transplantation has increased at a rate of 150 new cases per month. Liver transplantation itself rose 1.84-fold (from 160 to 295) from 1988 to 2004. However, the number of patients on the liver waiting list jumped 2.71-fold (from 553 to 1500). Consequently, the number of deaths on the liver waiting list moved to a higher level, from 321 to 671, increasing 2.09-fold. We have applied a mathematical model to analyze the potential impact of using a donation after cardiac death (DCD) policy on our liver transplantation program and on the waiting list. Five thousand one hundred people died because of accidents and other violent causes in our state in 2004; of these, only 295 were donors of liver grafts that were transplanted. The model assumed that 5% of these grafts would have been DCD. We found a relative reduction of 27% in the size of the liver transplantation waiting list if DCD had been used by assuming that 248 additional liver transplants would have been performed annually. In conclusion, the use of DCD in our transplantation program would reduce the pressure on our liver transplantation waiting list, reducing it by at least 27%. On the basis of this model, the projected number of averted deaths is about 41,487 in the next 20 years.
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Affiliation(s)
- Eleazar Chaib
- Liver and Transplantation Surgery Unit, Department of Gastroenterology, University of São Paulo School of Medicine, São Paulo, Brazil.
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Maciel-de-Freitas R, Peres RC, Souza-Santos R, Lourenço-de-Oliveira R. Occurrence, productivity and spatial distribution of key-premises in two dengue-endemic areas of Rio de Janeiro and their role in adult Aedes aegypti spatial infestation pattern. Trop Med Int Health 2008; 13:1488-94. [PMID: 18983276 DOI: 10.1111/j.1365-3156.2008.02162.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To evaluate: (1) the occurrence, maintenance, productivity, spatial distribution and premise condition index score of Aedes aegypti-infested houses and key-premises in a suburban district (Tubiacanga) and a slum (Favela do Amorim) of Rio de Janeiro and (2) the role of these factors in adult Ae. aegypti female spatial distribution. METHODS AND RESULTS A total of 2456 premises were inspected for immature and 1100 for adult collection. Key-premises corresponded to 16.08% and 17.86% of infested houses in Tubiacanga, and 13.5% and 11.1% in Favela do Amorim, during the dry and wet seasons, respectively. Key-premises held significantly more immature Ae. aegypti, pupae and larvae than infested houses in Favela do Amorim and Tubiacanga during the dry and wet seasons. In Favela do Amorim, key-premises had a significantly higher PCI score than infested but non-key houses. CONCLUSION The spatial distribution of key-premises and adult Ae. aegypti females was often congruent, indicating that key-premises influence the infestation pattern observed in the study areas.
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Abstract
On 9 June 2006 the Pan American Health Organization (PAHO) presented the Minister of Health of Brazil with the International Elimination of Transmission of Chagas' Disease Certificate. This act was the culmination of an intensive process that began in 1991 with the Southern Cone Initiative, a joint agreement between the governments of Argentina, Bolivia, Brazil, Chile, Paraguay, Uruguay and Peru, to control Chagas' disease by the elimination of the main vector, Triatoma infestans. This initiative has been highly successful and the prevalence area of the vector diminished rapidly in the last years. As a consequence, the current seroprevalence in children aged between 0 and 5 years is of the order of 10(-5), a clear indication that transmission, if it is occurring, is only accidental. In this review I calculate the basic reproduction number, R0, for Chagas' disease and demonstrate that its relatively low value (1.25) explains why vectorial transmission was interrupted relatively easily. In addition, I used a mathematical model to forecast how long the remaining cases of the disease, as well as the additional vertically transmitted cases will last.
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Affiliation(s)
- E Massad
- School of Medicine, The University of São Paulo, LIM 01/HCFMUSP, Brazil.
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48
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Pongsumpun P, Garcia Lopez D, Favier C, Torres L, Llosa J, Dubois MA. Dynamics of dengue epidemics in urban contexts. Trop Med Int Health 2008; 13:1180-7. [PMID: 18840157 DOI: 10.1111/j.1365-3156.2008.02124.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dengue, similar to other arboviral diseases, exhibits complex spatiotemporal dynamics. Even at town or village level, individual-based spatially explicit models are required to correctly reproduce epidemic curves. This makes modelling at the regional level (province, country or continent) very difficult and cumbersome. We propose here a first step to build a hierarchized model by constructing a simple analytical expression which reproduces the model output from macroscopic parameters describing each 'village'. It also turns out to be a good approximation of real urban epidermic outbreaks. Subsequently, a regional model could be built by coupling these equations on a lattice.
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Affiliation(s)
- P Pongsumpun
- Department of Mathematics and Computer Science, King Mongkut Institute of Technology, Bangkok, Thailand
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49
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Cost-effectiveness analysis of a hypothetical hepatitis C vaccine compared to antiviral therapy. Epidemiol Infect 2008; 137:241-9. [PMID: 18631422 DOI: 10.1017/s0950268808000873] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We propose a mathematical model to simulate the dynamics of hepatitis C virus (HCV) infection in the state of São Paulo, Brazil. We assumed that a hypothetical vaccine, which cost was taken to be the initial cost of the vaccine against hepatitis B exists and it is introduced in the model. We computed its cost-effectiveness compared with the anti-HCV therapy. The calculated basic reproduction number was 1.20. The model predicts that without intervention a steady state exists with an HCV prevalence of 3%, in agreement with the current epidemiological data. Starting from this steady state three interventions were simulated: indiscriminate vaccination, selective vaccination and anti-HCV therapy. Selective vaccination proved to be the strategy with the best cost-effectiveness ratio, followed by indiscriminate vaccination and anti-HCV therapy.
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50
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Gubbins S, Carpenter S, Baylis M, Wood JLN, Mellor PS. Assessing the risk of bluetongue to UK livestock: uncertainty and sensitivity analyses of a temperature-dependent model for the basic reproduction number. J R Soc Interface 2008; 5:363-71. [PMID: 17638649 PMCID: PMC2497440 DOI: 10.1098/rsif.2007.1110] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Since 1998 bluetongue virus (BTV), which causes bluetongue, a non-contagious, insect-borne infectious disease of ruminants, has expanded northwards in Europe in an unprecedented series of incursions, suggesting that there is a risk to the large and valuable British livestock industry. The basic reproduction number, R0, provides a powerful tool with which to assess the level of risk posed by a disease. In this paper, we compute R0 for BTV in a population comprising two host species, cattle and sheep. Estimates for each parameter which influences R0 were obtained from the published literature, using those applicable to the UK situation wherever possible. Moreover, explicit temperature dependence was included for those parameters for which it had been quantified. Uncertainty and sensitivity analyses based on Latin hypercube sampling and partial rank correlation coefficients identified temperature, the probability of transmission from host to vector and the vector to host ratio as being most important in determining the magnitude of R0. The importance of temperature reflects the fact that it influences many processes involved in the transmission of BTV and, in particular, the biting rate, the extrinsic incubation period and the vector mortality rate.
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Affiliation(s)
- Simon Gubbins
- Institute for Animal Health, Pirbright Laboratory, Ash Road, Pirbright, Surrey GU24 0NF, UK.
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