Modelos para implementar a vacinação contra dengue

In this work we propose a mathematical approach to estimate the dengue force of infection, the average age of dengue first infection, the optimum age to vaccinate children against dengue in a routine fashion and the optimum age interval to introduce the dengue vaccine in a mass vaccination campaign. The model is based on previously published models for vaccination against other childhood infections, which resulted in actual vaccination programmes in Brazil. The model was applied for three areas of distinct levels of endemicity of the city of Recife in Northeastern State of Pernambuco, Brazil. Our results point to an optimal age to introduce the dengue vaccine in the routine immunization programme at two years of age and an age interval to introduce a mass vaccination between three and 14 years of age.Neste trabalho propomos um modelo matemático para a estimativa da força de infecção, da idade média de primo-infecção, da idade ótima para vacinação de rotina e do intervalo ótimo de cobertura vacina em uma campanha para a introdução da vacina contra a dengue. O modelo baseia-se em publicações anteriores de desenhos de estratégias de vacinação contra outras infecções e que resultaram em estratégias de vacinação no Brasil. O modelo foi aplicado em três áreas com níveis endêmicos de dengue distintos na cidade de Recife, Pernambuco. Nossos resultados apontam para uma idade ótima de vacinação na rotina de dois anos de idade e para um intervalo de vacinação em campanha entre três e 14 anos

The Preventive Control of Zoonotic Visceral Leishmaniasis: Efficacy and Economic Evaluation.

Zoonotic Visceral Leishmaniasis (ZVL) is one of the world's deadliest and neglected infectious diseases, according to World Health Organization. This disease is one of major human and veterinary medical significance. The sandfly and the reservoir in urban areas remain among the major challenges for the control activities. In this paper, we evaluated five control strategies (positive dog elimination, insecticide impregnated dog collar, dog vaccination, dog treatment, and sandfly population control), considering disease control results and cost-effectiveness. We elaborated a mathematical model based on a set of differential equations in which three populations were represented (human, dog, and sandfly). Humans and dogs were divided into susceptible, latent, clinically ill, and recovery categories. Sandflies were divided into noninfected, infected, and infective. As the main conclusions, the insecticide impregnated dog collar was the strategy that presented the best combination between disease control and cost-effectiveness. But, depending on the population target, the control results and cost-effectiveness of each strategy may differ. More and detailed studies are needed, specially one which optimizes the control considering more than one strategy in activity

Theoretical impact of insecticide-impregnated school uniforms on dengue incidence in Thai children.

BACKGROUND: Children carry the main burden of morbidity and mortality caused by dengue. Children spend a considerable amount of their day at school; hence strategies that reduce human-mosquito contact to protect against the day-biting habits of Aedes mosquitoes at schools, such as insecticide-impregnated uniforms, could be an effective prevention strategy. METHODOLOGY: We used mathematical models to calculate the risk of dengue infection based on force of infection taking into account the estimated proportion of mosquito bites that occur in school and the proportion of school time that children wear the impregnated uniforms. PRINCIPAL FINDINGS: The use of insecticide-impregnated uniforms has efficacy varying from around 6% in the most pessimistic estimations, to 55% in the most optimistic scenarios simulated. CONCLUSIONS: Reducing contact between mosquito bites and human hosts via insecticide-treated uniforms during school time is theoretically effective in reducing dengue incidence and may be a valuable additional tool for dengue control in school-aged children. The efficacy of this strategy, however, is dependent on the compliance of the target population in terms of proper and consistent wearing of uniforms and, perhaps more importantly, the proportion of bites inflicted by the Aedes population during school time

Equilibrium analysis of a yellow Fever dynamical model with vaccination.

We propose an equilibrium analysis of a dynamical model of yellow fever transmission in the presence of a vaccine. The model considers both human and vector populations. We found thresholds parameters that affect the development of the disease and the infectious status of the human population in the presence of a vaccine whose protection may wane over time. In particular, we derived a threshold vaccination rate, above which the disease would be eradicated from the human population. We show that if the mortality rate of the mosquitoes is greater than a given threshold, then the disease is naturally (without intervention) eradicated from the population. In contrast, if the mortality rate of the mosquitoes is less than that threshold, then the disease is eradicated from the populations only when the growing rate of humans is less than another threshold; otherwise, the disease is eradicated only if the reproduction number of the infection after vaccination is less than 1. When this reproduction number is greater than 1, the disease will be eradicated from the human population if the vaccination rate is greater than a given threshold; otherwise, the disease will establish itself among humans, reaching a stable endemic equilibrium. The analysis presented in this paper can be useful, both to the better understanding of the disease dynamics and also for the planning of vaccination strategies

Estudos sobre mosquitos (Diptera: Culicidae) e ambiente antrópico: 5- Desenvolvimento de Anopheles albitarsis em campos de arroz irrigados na região sudeste do Brasil

Studies on breeding Anopheles albitarsis and association with rice growth in irrigated paddy fields were carried out during the rice cultivation cycle from December 1993 to March 1994. This period corresponded to the length of time of permanent paddy flooding. Breeding occurred in the early stage up until five weeks after transplantation when rice plant height was small. That inverse correlation may give potential direction to control measures.Apresentam-se os resultados de observações sobre desenvolvimento da densidade larval de Anopheles albitarsis em criadouros representados por campos de arroz artificialmente irrigados, de dezembro de 1993 a março de 1994. Esse espaço de tempo correspondeu a período de inundação permanente iniciado com o transplante. Verificou-se relação inversa entre a densidade de larvas e a altura atingida pelas plantas de arroz. Assim, praticamente a produção das formas imaturas ocorreu ao longo das cinco primeiras semanas de inundação. O rendimento da margem dos campos de cultivo foi cerca do dobro daquele observado na área interna. Esse fenômeno não logrou explicação satisfatória apenas pelo fator insolação. Pode-se argumentar que a vegetação marginal, pela sua maior diversidade, possa oferecer maiores oportunidades de sobrevivência para as larvas, mediante abrigo e alimentação. De qualquer maneira, essas observações concordam com o verificado em outras regiões e possibilitam nortear a aplicação de eventuais medidas de controle

Studies on mosquitoes (Diptera: Culicidae) and anthropic environment: 9- Synanthropy and epidemiological vector role of Aedes scapularis in South-Eastern Brazil

Behaviour comparisons of Aedes scapularis and Ae. serratus are presented. Results were obtained by sampling Aedes adult mosquitoes at several places in the rural anthropic environment in the Ribeira Valley region of S. Paulo State, Brazil. Aedes dominance was shared by those two species, but Ae. scapularis Sshowed a clear tendency to frequent the modified environment, while Ae. serratus was to be found in the more preserved ones, here represented by the vestigial patchy forests. Regarding the open cultivated land and the dwelling environments, Ae. scapularis preponderates. Considering the regional developmental phases, this mosquito showed a remarkable increase in the modified environment differently from Ae. serratus that underwent a considerable decrease in migrating from the forest to the anthropic environment. As a consequence of these results it is reasonable to conclude that Ae. scapularis may be considered as an epidemiologically efficient vector and that it quite probably played this role in the Rocio encephalitis and other arbovirus epidemics.Relatam-se os resultados de coletas regulares de adultos de culicídeos Aedes, levadas a efeito em ambiente antrópico do Vale do Ribeira, SP, Brasil, ao longo do período de agosto de 1992 a dezembro de 1993. As coletas foram realizadas em várias áreas correspondentes a matas residuais, a ambiente aberto cultivado e a meio domiciliar. A dominância dividiu-se entre Ae. scapularis e Ae. serratus, porém não de maneira equivalente para as diversas áreas pesquisadas. O primeiro revelou nítida tendência ao predomínio no ambiente artificial representado pela área aberta cultivada e pelo domicílio humano. Quanto ao segundo, evidenciou-se nítida preferência pelo meio das matas residuais. Considerando este como remanescente da primitiva cobertura florestal da área, os outros foram tidos como fase posteriormente desenvolvida em virtude da atividade humana. Assim procedendo, compararam-se as duas fases em relação as duas espécies. Como resultado do cálculo dos índices de mudança, pode-se estimar que a população de Ae. scapularis cresceu mais de 16 vezes com a transformação do ambiente natural enquanto que a de Ae. serratus, nas mesmas cirunstâncias, sofreu decréscimo de 284 vezes. Tais dados, aliados ao predomínio de Ae. scapularis na isca humana do ambiente domiciliar, tornam lícita a conclusão deste culicídeo ser encarado como vetor biológico epidemiologicamente importante de doenças ao homem e animais. Assim sendo, é de se admitir ter desempenhado esse papel transmissor quando da epidemia de encefalite por virus Rocio, além de outras arboviroses, que ocorreu na região do Vale do Ribeira

Studies on mosquitoes (Diptera: Culicidae) and anthropic environment: 7- Behaviour of adults Nyssorhynchus anophelines with special reference to Anopheles albitarsis s.l. in South-Eastern Brazil

Relatam-se os resultados obtidos com coletas levadas a efeito em áreas do Vale do Ribeira, SP (Brasil) e mediante o emprego de armadilhas tipo Shannon. As evidências obtidas mostraram clara associação com o cultivo de arroz irrigado na Fazenda Experimental de Pariquera-Açu. Tudo leva a crer que ali ocorra concentração populacional desse complexo na qual pôde-se diferenciar duas espécies, designadas como A e B. A espécie B predominou francamente em todas as coletas. No ambiente domiciliar foi empregada a isca humana nas coletas efetuadas regularmente no intra e no peridomicílio. Em ambas situações foram encontradas as duas espécies, com baixo valor geral da média de Williams correspondente a 0,2. Considerando-se separadamente os resultados mensais, pôde-se obter valor máximo de 1,6. Não foi possível detectar qualquer diferença entre os dois ambientes, no que concerne à freqüência de ambas as espécies do complexo.Results obtained with catches performed at several sites of the Ribeira Valley, SP (Brazil) are reported. Collections with Shannon type traps showed a concentration of An.albitarsis s.l. in the Experimental Farm of Pariquera-Açu County, associated with the development of irrigated rice cultivation. Two species of the complex, named A and B, were recognized. Species B predominated in the samples. Indoor and outdoor crepuscular human bait captures were performed a the domiciliary environment. The two species showed a generally low William's media valve of 0.2, the highest value obtained was 1.6. No differences were found between indoor and outdoor behaviours between the two species of the complex

Estudos sobre mosquitos (Diptera: Culicidae) e ambiente antrópico: 3 - Coleta de formas adultas no sistema de irrigação artificial para cultivo de arroz e emergência de Anopheles albitarsis na região sudeste do Brasil

Relatam-se os resultados obtidos com a coleta regular de Culicidae adultos no período de janeiro de 1992 a Janeiro de 1993, levadas a efeito no sistema artificialmente irrigado da Estação Experimental do Vale do Ribeira, SP -Brasil. Evidenciou-se a emergência de Anopheles albitarsis como uma das espécies de mosquitos prevalentes no sistema irrigado. Esse aspecto, acrescido da sua prática ausência no meio natural primitivo ou mesmo nas matas residuais locais, levou à hipótese de se tratar de culicídeo eusinantrópico. As condições artificiais aparentemente favoreceram também Aedes scapularis, Culex nigripalpus e Cx. ribeirensis. A comparação das biodiversidades encontradas nos ambientes, antrópico e natural, não foi acentuada sob o ponto de vista quantitativo, mas o foi quanto à feição qualitativa. Aquelas espécies de maior prevalência mostraram incidências relativamente alternadas ao longo do período anual. A presença de An. albitarsis foi mais prevalente nas épocas de inundação dos campos de arroz, enquanto Ae. scapularis mostrou-se mais freqüente por ocasião do período inicial de esvaziamento dos arrozáis irrigados. Tais resultados permitiram considerar Ae. scapularis, Cx. nigripalpus e Cx. ribeirensis como culicídeos hemisinantrópicos. É de se admitir que a adoção da técnica de irrigação artificial para o desenvolvimento agrícola da região possa vir a favorecer o incremento de endemias veiculadas por mosquitos, como a malária.A study of adult Culicidae ecology was carried out from January 1992 through January 1993 at the rice irrigation system of the Ribeira Valley Experimental Station. The adaptation of Anopheles albitarsis to the anthropic environment became evident through the adult collections made at its various habitats represented by the irrigation system and the edge of the residual pond, as well as at those made within the local patchy residual woods. Other potential disease vectors were prevalent in the irrigated system too. There were Aedes scapularis, Culex nigripalpus and Cx. ribeirensis that were collected at various habitats. Remarkable differences among their prevalences were obtained such as between the natural forest and anthropic environments. In the former An. albitarsis was practically non-existent, thus suggesting that it might be considered as eusynathropic. As the populations of other species seemed to increase in the anthropic environment, they may be regarded as hemisynanthropes. Observations suggest the hypothesis that the development of irrigated land may be a factor in the emergence of An. albitarsis, and some other species, as well as the possibility of an increase in the transmission of mosquito-borne diseases such as malaria

Vitamin B1 as a scavenger of reactive oxygen species photogenerated by vitamin B2

Kinetics and mechanism of photoprocesses generated by visible light-irradiation of the system riboflavin (Rf, vitamin B2) plus Thiamine (Th) and Thiamine pyrophosphate (ThDP), representing vitamin B1, was studied in pH 7 water. A weak dark complex vitamin B2-vitamin B1, with a mean value of 4 ± 0.4 m-1 is formed. An intricate mechanism of competitive reactions operates upon photoirradiation, being the light only absorbed by Rf. Th and ThDP quench excited singlet and triplet states of Rf, with rate constants in the order of 109 and 106m-1s-1, respectively. With Vitamin B1 in a concentration similar to that of dissolved molecular oxygen in water, the quenching of triplet excited Rf by the latter is highly predominant, resulting in the generation of O2( 1Δg). Superoxide radical anion was not detected under work conditions. A relatively slow O2(1Δ g)-mediated photodegradation of Th and ThDP was observed. Nevertheless, Th and especially ThDP behave as efficient physical deactivators of O2(1Δg). The thiazol structure in vitamin B1 appears as a good scavenger of this reactive oxygen species. This characteristic, that presents at vitamin B1 as a potential photoprotector of biological entities against O2(1Δg) attack, was been experimentally confirmed employing the protein lisozime as a photo-oxidizable target. © 2010 The American Society of Photobiology.Fil: Natera, Jose Eduardo. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; ArgentinaFil: Massad, Walter Alfredo. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; ArgentinaFil: Garcia, Norman Andino. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin