Search

BackgroundPassively collected malaria case data are the foundation for public health decision making. However, because of population-level immunity, infections might not always be sufficiently symptomatic to prompt individuals to seek care. Understanding the proportion of all Plasmodium spp infections expected to be detected by the health system becomes particularly paramount in elimination settings. The aim of this study was to determine the association between the proportion of infections detected and transmission intensity for Plasmodium falciparum and Plasmodium vivax in several global endemic settings.MethodsThe proportion of infections detected in routine malaria data, P(Detect), was derived from paired household cross-sectional survey and routinely collected malaria data within health facilities. P(Detect) was estimated using a Bayesian model in 431 clusters spanning the Americas, Africa, and Asia. The association between P(Detect) and malaria prevalence was assessed using log-linear regression models. Changes in P(Detect) over time were evaluated using data from 13 timepoints over 2 years from The Gambia.FindingsThe median estimated P(Detect) across all clusters was 12·5% (IQR 5·3-25·0) for P falciparum and 10·1% (5·0-18·3) for P vivax and decreased as the estimated log-PCR community prevalence increased (adjusted odds ratio [OR] for P falciparum 0·63, 95% CI 0·57-0·69; adjusted OR for P vivax 0·52, 0·47-0·57). Factors associated with increasing P(Detect) included smaller catchment population size, high transmission season, improved care-seeking behaviour by infected individuals, and recent increases (within the previous year) in transmission intensity.InterpretationThe proportion of all infections detected within health systems increases once transmission intensity is sufficiently low. The likely explanation for P falciparum is that reduced exposure to infection leads to lower levels of protective immunity in the population, increasing the likelihood that infected individuals will become symptomatic and seek care. These factors might also be true for P vivax but a better understanding of the transmission biology is needed to attribute likely reasons for the observed trend. In low transmission and pre-elimination settings, enhancing access to care and improvements in care-seeking behaviour of infected individuals will lead to an increased proportion of infections detected in the community and might contribute to accelerating the interruption of transmission.FundingWellcome Trust.

Author(s): Daniel A. Pfeffer, Benedikt Ley, Rosalind E. Howes, Patrick Adu, Mohammad Shafiul Alam, Pooja Bansil, Yap Boum, Marcelo Brito, Pimlak Charoenkwan, Archie Clements, Liwang Cui, Zeshuai Deng, Ochaka Julie [...]

Objective To study dengue vector breeding patterns under a variety of conditions in public and private spaces; to explore the ecological, biological and social (eco-bio-social) factors involved in vector breeding and viral transmission, and to define the main implications for vector control. Methods In each of six Asian cities or periurban areas, a team randomly selected urban clusters for conducting standardized household surveys, neighbourhood background surveys and entomological surveys. They collected information on vector breeding sites, people's knowledge, attitudes and practices surrounding dengue, and the characteristics of the study areas. AII premises were inspected; larval indices were used to quantify vector breeding sites, and pupal counts were used to identify productive water container types and as a proxy measure for adult vector abundance. Findings The most productive vector breeding sites were outdoor water containers, particularly if uncovered, beneath shrubbery and unused for at least one week. Peridomestic and intradomestic areas were much more important for pupal production than commercial and public spaces other than schools and religious facilities. A complex but non-significant association was found between water supply and pupal counts, and lack of waste disposal services was associated with higher vector abundance in only one site. Greater knowledge about dengue and its transmission was associated with lower mosquito breeding and production. Vector control measures (mainly larviciding in one site) substantially reduced larval and pupal counts and 'pushed' mosquito breeding to alternative containers. Conclusion Vector breeding and the production of adult Aedes aegypti are influenced by a complex interplay of factors. Thus, to achieve effective vector management, a public health response beyond routine larviciding or focal spraying is essential. Objectif Etudier les schemas de reproduction des vecteurs de la dengue dans diverses conditions et dans des espaces publics et prives, rechercher les facteurs ecologiques, biologiques et sociaux impliques dans la reproduction de ces vecteurs et la transmission virale et determiner les principales implications pour la lutte antivectorielle. Methodes Dans six grandes villes ou zones periurbaines d'Asie, une equipe a selectionne au hasard des groupes urbains pour mener des enquetes aupres des rnenages standardisees, des enquetes de voisinage et des enquetes entomologiques. Les equipes ont recueilli des informations sur les sites de reproduction des vecteurs, les connaissances des habitants, les attitudes et les pratiques a propos de la dengue et les caracteristiques des zones etudiees. Tous les lieux ont ete inspectes; les equipes ont utilise les indices larvaires pour evaluer sur le plan quantitatif les sites de reproduction vectorielle et le decompte des pupes pour identifier les types d'objets renfermant de l'eau les plus productifs et pour servir de mesure indirecte de l'abondance des vecteurs adultes. Resultats Les sites de reproduction les plus productifs etaient les objets renfermant de I'eau situes a I'exterieur, en particulier lorsqu'ils etaient depourvus de couvercle, sous des broussailles et inutilises pendant au moins une semaine. Les zones peridornestiques et intradornestiques jouaient un role beaucoup plus important dans la production de pupes que les espaces commerciaux et publics autres que les ecoles et les edifices religieux. Une association complexe, mais non significative, a ete relevee entre l'approvisionnement en eau et le nombre de pupes decomptees et on a constate un lien entre le manque de services d'elimination des dechets et une plus grande abondance des vecteurs sur un site seulement. La presence de meilleures connaissances sur la dengue et sa transmission chez les habitants etait egalement associee une reproduction et a une production plus limitees des vecteurs. Les mesures de lutte antivectorielle (principalement I'application de larvicide sur le site) ont permis de reduire substantiellement les nin de larves et de pupes eta <> la reproduction des moustiques vers d'autres recipients. Conclusion Un ensemble interactif complexe de facteurs influe sur la reproduction et la production de moustiques Aedes aegypti adultes. Ainsi, pour gerer efficacement les populations vectorielles, une reponse de sante publique globale, allant au-dela des traitements larvicides de routine ou de la pulverisation focale, est indispensable. Objetivo Estudiar las caracteristicas de la reproduccion del vector del dengue en diversas condiciones en espacios publicos y privados; investigar los aspectos ecologicos, biologicos y sociales (ecobiosociales) que intervienen en la reproduccion del vector y la transmision del virus, y determinar las principales implicaciones para la lucha antivectorial. Metodos En cada una de las seis zonas urbanas o periurbanas de Asia estudiadas, un equipo selecciono al azar conglomerados urbanos para realizar encuestas de hogares normalizadas, encuestas basales del vecindario y estudios entomologicos. Reunieron informacion sobre los criaderos de vectores, los conocimientos de la gente al respecto, las actitudes y practicas relacionadas con el dengue, y las caracteristicas de las zonas estudiadas. Se inspeccionaron todos los locales, y se usaron los indices larvarios para cuantificar los criaderos del vector, y el numero de pupas para distinguir el tipo de contenedores de agua productivos y como indicador sustitutivo de la abundancia de vectores adultos. Resultados Los criaderos de vectores mas productivos fueron los contenedores de agua situados al aire libre, sobre todo los que estaban sin cubrir o debajo de arbustos, y los que no habian sido utilizados por lo menos en una semana. Las areas peridomesticas e intradomesticas contribuian a la produccion de pupas mucho mas que los espacios comerciales y publicos, exceptuando las escuelas y los centros religiosos. Se observo una relacion compleja aunque no significativa entre el suministro de agua y el numero de pupas, y la falta de servicios de evacuacion de desechos se asocio a una mayor abundancia de vectores en un solo sitio. La posesion de mayores conocimientos sobre el dengue y su transmision se asocio a una menor reproduccion y produccion de'mosquitos. Las medidas de lucha antivectorial (principalmente la aplicacion de larvicidas en un sitio) lograron reducir sustancialmente el numero de larvas y pupas y los criaderos de mosquitos hacia otros contenedores. Conclusion La reproduccion del vector y la produccion de Aedes aegypti adulto dependen de una compleja interaccion de factores. En consecuencia, para lograr controlar eficazmente los vectores, es fundamental articular una respuesta de salud publica que no se limite a la aplicacion de larvicidas o el rociamiento localizado., Introduction Dengue, which is the fastest re-emerging arboviral disease in the world, imposes a heavy economic and health burden on countries, families and individual patients. (1,2) In the absence of [...]

Early diagnosis and treatment for malaria has a significant impact on the severity of the disease and contributes to the interruption of its transmission. Fourteen high-risk families and nine locality-matched families, with no recent history of malaria, participated in an ethnographic study which aimed to document malaria episodes and to examine treatment paths for fevers locally termed malarya and perceived to be malaria. The study, conducted in Morong, Bataan, a low malaria endemic area in the Philippines, used a combination of qualitative and quantitative methods over a period of 12 months. Six treatment categories were identified; self-treatment with Western medicines and clinic consultations had almost equal frequencies. Twenty-six treatment paths were recognised which consisted of the six categories singly or in combination. More than 80% of the undiagnosed malarya illnesses were treated with antimalarials of inappropriate dosages. More adult men than women self-treated, but there was no significant difference by gender in terms of clinic consultation for illness. The majority of clinic consultations were made for young children. The implications for control are discussed.

Five human cases of infection with the simian malaria parasite Plasmodium knowlesi from Palawan, the Philippines, were confirmed by nested PCR. This study suggests that this zoonotic infection is found [...]