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Climate change and future potential temperature dependent malaria transmission gates

Author:
Schröder, W., Holy, M., Schmidt, G., Pesch, R.
Source:
Environmental sciences Europe 2010 v.22 no.3 pp. 177-187
ISSN:
2190-4707
Subject:
Anopheles atroparvus, Internet, Plasmodium vivax, air temperature, algorithms, climate change, climate models, disease transmission, dynamic models, geographic information systems, habitats, information systems, land classification, malaria, microclimate, pathogens, population density, reproduction, risk, secondary infection, soil, water balance, Germany
Abstract:
Background, aim and scope On behalf of the Centre of Excellence for Climate Effects and Adaption (KomPass) of the German Federal Environment Agency (UBA) an Expert Information System on Climate Change and Adaption (FISKA) was developed. FISKA shall provide the governmental institutions with basic information and models on climate change impacts for the development and accomplishment of adaption strategies. In this paper the impact model on potential temperature-dependent malaria transmissions is presented. It shows how, together with the REMO and WettReg climate models implemented in FISKA, areas at risk of malaria can be identified.Materials and methods FISKA was developed as an open and modular expert information system and allows the exchange of data and information with other institutions. Climate change impacts are implemented as calculation engines. The system allows for implementing additional data and impact models to improve existing impact models. For the calculation of the temperature-dependent potential secondary malaria infections the basic reproduction rate was used and the according algorithms were implemented in two calculation engines. One engine allows the calculation of the secondary infections and the other allows the calculation of the seasonal transmission gates. Measured air temperatures for the period 1961–2007 were provided by the German Meteorological Service (DWD), data on future air temperatures were extracted from the climate models REMO and WettReg for the climate reference periods 1991–2020, 2021–2050, and 2051–2080. The respective secondary infections and the resulting seasonal transmission gates for each period were regionalised on the basis of an ecological land classification to analyse significant ecoregional differences.Results Comparing the climate reference period 1961–1990 and the following period 1991–2007, the proportion of Germany featuring a potential seasonal malaria transmission gate of one or rather two months has been reduced in favour of a three months transmission gate. Accordingly, in the period 1991–2007 malaria transmissions during three months are possible on 70 % of the German territory instead of 26 % in 1961–1990. The percentage of a four months transmission gate has increased from 0.02 % to 0.76 %, and even a five months transmission is possible on 0.15 % of Germany. For future periods the number of potential secondary infections increases and further extensions of the seasonal transmission gates were revealed. In case of REMO A1B in 2051–2080, almost whole Germany features thermal conditions allowing malaria transmissions during four or rather five months.Discussion Rising air temperatures lead to changes in the spatial structure of the ecological elementary factor temperature, which can, under otherwise identical conditions, facilitate the reproduction of pathogens (here Plasmodium vivax) and vectors (here Anopheles atroparvus) as well as the spread of diseases. The basic reproduction rate serves the calculation of secondary malaria infections, which are the infections of host by a vector under the assumption that every member of the host population is susceptible for the pathogen. Improved thermal conditions alone do not necessarily imply the development of a malaria epidemic. Other factors like population density or medical care and the presence of vector habitats are of major importance, however, not considered by the calculation engines. The example of malaria is intended to be a model for a range of temperature-dependent vector-borne diseases.Conclusions The impact model on temperature-dependent malaria infections shows exemplarily the information content and functionality of FISKA. Data and functionality of FISKA serve as an expert information system for the detection of risks due to climate change. The results can be published as interactive maps via the FISKA internet interface. From a technical point of view, every impact model based on a calculation engine can be implemented and published via the web interface, provided that the impact models and the resulting risk maps rely on scientific reliable assumptions and are documented comprehensively.Recommendations and perspectives An improvement of FISKA considering the European scale is technically possible. It would require the development of GIS- and model applications on the basis of Europe-wide basic and specific data. For small-scale model runs a dynamic modelling of the water balance including soil hydrology as well as consideration of microclimate effects are required.
Agid:
5732541