Climate Suitability for Stable Malaria Transmission in Zimbabwe Under Different Climate Change Scenarios
ABSTRACT Climate is one factor that determines the potential range of malaria. As such, climate change may work with or against efforts
to bring malaria under control. We developed a model of future climate suitability for stable Plasmodium falciparum malaria transmission in Zimbabwe. Current climate suitability for stable malaria transmission was based on the MARA/ARMA
model of climatic constraints on the survival and development of the Anopheles vector and the Plasmodium falciparum malaria parasite. We explored potential future geographic distributions of malaria using 16 projections of climate in 2100.
The results suggest that, assuming no future human-imposed constraints on malaria transmission, changes in temperature and
precipitation could alter the geographic distribution of malaria in Zimbabwe, with previously unsuitable areas of dense human
population becoming suitable for transmission. Among all scenarios, the highlands become more suitable for transmission, while
the lowveld and areas with low precipitation show varying degrees of change, depending on climate sensitivity and greenhouse
gas emission stabilization scenarios, and depending on the general circulation model used. The methods employed can be used
within or across other African countries.
- SourceAvailable from: Kacey C Ernst[Show abstract] [Hide abstract]
ABSTRACT: Climate influences dengue ecology by affecting vector dynamics, agent development, and mosquito/human interactions. While these relationships are known, the impact climate change will have on transmission is unclear. Climate-driven statistical and process-based models are being used to refine our knowledge of these relationships and predict the effects of projected climate change on dengue fever occurrence, but results have been inconsistent. We identify major climatic influences on dengue virus ecology and evaluate the ability of climate-based dengue models to describe associations between climate and dengue, simulate outbreaks, and project the impacts of climate change. We review the evidence for direct and indirect relationships between climate and dengue generated from laboratory studies, field studies, and statistical analyses of associations between vectors, dengue fever incidence, and climate conditions. The potential contribution of climate driven, process-based dengue models is assessed, and suggestions are provided to improve their performance. Relationships between climate variables and factors that influence dengue transmission are complex. A climate variable may increase dengue transmission potential through one aspect of the system, while simultaneously decreasing potential through another. This complexity may at least partly explain inconsistencies in statistical associations between dengue and climate. Process-based models can account for the complex dynamics but often omit important aspects of dengue ecology, notably virus development and interactions between host species. Synthesizing and applying current knowledge of climatic effects on all aspects of dengue virus ecology will help direct future research and enable better projections of climate change effects on dengue incidence.Environmental Health Perspectives 09/2013; · 7.26 Impact Factor
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ABSTRACT: Poikilothermic disease vectors can respond to altered climates through spatial changes in both population size and phenology. Quantitative descriptors to characterize, analyze and visualize these dynamic responses are lacking, particularly across large spatial domains. In order to demonstrate the value of a spatially explicit, dynamic modeling approach, we assessed spatial changes in the population dynamics of Ixodes scapularis, the Lyme disease vector, using a temperature-forced population model simulated across a grid of 4 × 4 km cells covering the eastern United States, using both modeled (Weather Research and Forecasting (WRF) 3.2.1) baseline/current (2001-2004) and projected (Representative Concentration Pathway (RCP) 4.5 and RCP 8.5; 2057-2059) climate data. Ten dynamic population features (DPFs) were derived from simulated populations and analyzed spatially to characterize the regional population response to current and future climate across the domain. Each DPF under the current climate was assessed for its ability to discriminate observed Lyme disease risk and known vector presence/absence, using data from the US Centers for Disease Control and Prevention. Peak vector population and month of peak vector population were the DPFs that performed best as predictors of current Lyme disease risk. When examined under baseline and projected climate scenarios, the spatial and temporal distributions of DPFs shift and the seasonal cycle of key questing life stages is compressed under some scenarios. Our results demonstrate the utility of spatial characterization, analysis and visualization of dynamic population responses-including altered phenology-of disease vectors to altered climate.ISPRS international journal of geo-information. 09/2013; 2(3):645-664.
Article: Malaria and climate change[Show abstract] [Hide abstract]
ABSTRACT: 1 . There are several species of anopheles mosquitoes that transmit malaria however, the most efficient of these vectors are found in Africa and these are namely Anopheles gambiae, An. arabiensis and An. funestus . Two of these vectors An. gambiae and An. funestus more than 90% of their blood meals from human beings thus optimizing the chance of transmitting the malaria parasite 2 . T he development rate of mosquito larvae is temperature dependent: below 16°C development of An. gambiae mosquitoes stops and below 14°C they die. In cold temperatures the larvae develop very slowly and in many cases they may be eaten by predators and may never live to transmit the disease. Once larvae emerge to become adults, the rate at which they feed on man is dependent upon the ambient temperature. At 17°C the female mosquitoes ( An. gambiae ) feed on humans every 4 days while at 25°C they take blood meals from humans every 2 days. Rainfall increases the breeding habitats for mosquitoes leading to increased population sizes and the rate of malaria transmission. The rate of development of the malaria parasite in female mosquitoes is very sensitive to ambient temperature. The rate of the parasite development in the female mosquito has an exponential relationship to temperature. This means that very small increase in external temperature will reduce the time it takes for the parasite to mature several fold. In Western Kenya a 0.5°C increase in temperature since the 1970's can explain the eight-fold increase in malaria cases (Pascual 2009 http://www.ipsnews.net/news). The biology of malaria transmission is thus very sensitive to changes in the weather and climate. It is now clear that climate change has taken place worldwide and some of the impacts are now obvious. For example many of the mountains in Africa, South America and even in New Zealand have lost glacier. Ice in the North Pole too has been melting at an unprecedented rate (http://nsidc.org/sotc/glacier_balance.html). In addition to the world becoming warmer there has been an observation of stronger and more frequent extreme events in recent times. These are signs of strong climate variability. Events such as the El Ni ńo phenomenon can seasonally increase the local temperature and rainfall, leading to increased breeding of malaria vectors and the rate of development of malaria parasites in the vectors 3