Feeding strategies of anthropophilic mosquitoes result in increased risk of pathogen transmission
Scott, T.W. ; Takken, W. - \ 2012
Trends in Parasitology 28 (2012)3. - ISSN 1471-4922 - p. 114 - 121.
aedes-aegypti diptera - anopheles-gambiae diptera - ideal free distribution - sensu-stricto diptera - puerto-rico - human-blood - body-size - plasmodium-falciparum - dengue vector - defensive behavior
Vector-borne disease specialists have traditionally assumed that in each egg-laying cycle mosquitoes take a single bloodmeal that is used for egg development and feed on plant sugars for flight and production of energy reserves. Here we review research showing that for two of the most important vectors of human pathogens (Anopheles gambiae and Aedes aegypti) imbibing multiple bloodmeals during a gonotrophic cycle while foregoing sugar feeding is a common behaviour, not an exception. By feeding preferentially and frequently on human blood these species increase their fitness and exponentially boost the basic reproduction rate of pathogens they transmit. Although the epidemiological outcome is similar, there are important differences in processes underlying frequent human contact by these species that merit more detailed investigation.
Global Status of DDT and Its Alternatives for Use in Vector Control to Prevent Disease
Berg, H. van den - \ 2009
Environmental Health Perspectives 117 (2009)11. - ISSN 0091-6765 - p. 1656 - 1663.
insecticide-treated nets - resistance management strategies - anopheles-gambiae diptera - african malaria vectors - south-africa - sri-lanka - organochlorine pesticides - breast-cancer - environmental-management - child-mortality
Objective - I review the status of dichlorodiphenyltrichloroethane (DDT), used for disease vector control, along with current evidence on its benefits and risks in relation to the available alternatives. Data sources and extraction - Contemporary data on DDT use were largely obtained from questionnaires and reports. I also conducted a Scopus search to retrieve published articles. Data synthesis - DDT has been recommended as part of the arsenal of insecticides available for indoor residual spraying until suitable alternatives are available. Approximately 14 countries use DDT for disease control, and several countries are preparing to reintroduce DDT. The effectiveness of DDT depends on local settings and merits close consideration in relation to the alternatives. Concerns about the continued use of DDT are fueled by recent reports of high levels of human exposure associated with indoor spraying amid accumulating evidence on chronic health effects. There are signs that more malaria vectors are becoming resistant to the toxic action of DDT, and that resistance is spreading to new countries. A comprehensive cost assessment of DDT versus its alternatives that takes side effects into account is missing. Effective chemical methods are available as immediate alternatives to DDT, but the choice of insecticide class is limited, and in certain areas the development of resistance is undermining the efficacy of insecticidal tools. New insecticides are not expected in the short term. Nonchemical methods are potentially important, but their effectiveness at program level needs urgent study. Conclusions - To reduce reliance on DDT, support is needed for integrated and multipartner strategies of vector control and for the continued development of new technologies. Integrated vector management provides a framework for developing and implementing effective technologies and strategies as sustainable alternatives to reliance on DDT
Observations and model estimates of diurnal water temperature dynamics in mosquito breeding sites in western Kenya
Paaijmans, K.P. ; Jacobs, A.F.G. ; Takken, W. ; Heusinkveld, B.G. ; Githeko, A.K. ; Dicke, M. ; Holtslag, A.A.M. - \ 2008
Hydrological Processes 22 (2008)24. - ISSN 0885-6087 - p. 4789 - 4801.
anopheles-gambiae diptera - aquatic stages - malaria transmission - culicidae larvae - land-cover - habitats - survival - highlands - reservoir - village
Water temperature is an important determinant of the growth and development of malaria mosquito immatures. To gain a better understanding of the daily temperature dynamics of malaria mosquito breeding sites and of the relationships between meteorological variables and water temperature, three clear water pools (diameter × depth: 0·16 × 0·04, 0·32 × 0·16 and 0·96 × 0·32 m) were created in Kenya. Continuous water temperature measurements at various depths were combined with weather data collections from a meteorological station. The water pools were homothermic, but the top water layer differed by up to about 2 °C in temperature, depending on weather conditions. Although the daily mean temperature of all water pools was similar (27·4-28·1 °C), the average recorded difference between the daily minimum and maximum temperature was 14·4 °C in the smallest versus 7·1 °C in the largest water pool. Average water temperature corresponded well with various meteorological variables. The temperature of each water pool was continuously higher than the air temperature. A model was developed that predicts the diurnal water temperature dynamics accurately, based on the estimated energy budget components of these water pools. The air-water interface appeared the most important boundary for energy exchange processes and on average 82-89% of the total energy was gained and lost at this boundary. Besides energy loss to longwave radiation, loss due to evaporation was high; the average estimated daily evaporation ranged from 4·2 mm in the smallest to 3·7 mm in the largest water pool
Establishment of a large semi-field system for experimental study of African malaria vector ecology and control in Tanzania
Ferguson, H.M. ; Ng'habi, K.R. ; Walder, T. ; Kadungula, D. ; Moore, S.J. ; Lyimo, I. ; Russell, T.L. ; Urassa, H. ; Mshinda, H. ; Killeen, G.F. ; Knols, B.G.J. - \ 2008
Malaria Journal 7 (2008). - ISSN 1475-2875 - 15 p.
anopheles-gambiae diptera - germ-line transformation - insecticide-treated nets - genetic-control systems - aedes-aegypti - western kenya - plasmodium-falciparum - transgenic mosquitos - transmitting mosquitos - laboratory populations
Background - Medical entomologists increasingly recognize that the ability to make inferences between laboratory experiments of vector biology and epidemiological trends observed in the field is hindered by a conceptual and methodological gap occurring between these approaches which prevents hypothesis-driven empirical research from being conducted on relatively large and environmentally realistic scales. The development of Semi-Field Systems (SFS) has been proposed as the best mechanism for bridging this gap. Semi-field systems are defined as enclosed environments, ideally situated within the natural ecosystem of a target disease vector and exposed to ambient environmental conditions, in which all features necessary for its life cycle completion are present. Although the value of SFS as a research tool for malaria vector biology is gaining recognition, only a few such facilities exist worldwide and are relatively small in size (<100 m2). Methods - The establishment of a 625 m2 state-of-the-art SFS for large-scale experimentation on anopheline mosquito ecology and control within a rural area of southern Tanzania, where malaria transmission intensities are amongst the highest ever recorded, is described. Results A greenhouse frame with walls of mosquito netting and a polyethylene roof was mounted on a raised concrete platform at the Ifakara Health Institute. The interior of the SFS was divided into four separate work areas that have been set up for a variety of research activities including mass-rearing for African malaria vectors under natural conditions, high throughput evaluation of novel mosquito control and trapping techniques, short-term assays of host-seeking behaviour and olfaction, and longer-term experimental investigation of anopheline population dynamics and gene flow within a contained environment that simulates a local village domestic setting. Conclusion - The SFS at Ifakara was completed and ready for use in under two years. Preliminary observations indicate that realistic and repeatable observations of anopheline behaviour are obtainable within the SFS, and that habitat and climatic features representative of field conditions can be simulated within it. As work begins in the SFS in Ifakara and others around the world, the major opportunities and challenges to the successful application of this tool for malaria vector research and control are discussed.