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This Article Appeared in a Journal Published by Elsevier. the Attached This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Veterinary Parasitology 163 (2009) 264–280 Contents lists available at ScienceDirect Veterinary Parasitology journal homepage: www.elsevier.com/locate/vetpar Climate change effects on trematodiases, with emphasis on zoonotic fascioliasis and schistosomiasis Santiago Mas-Coma *, Maria Adela Valero, Maria Dolores Bargues Departamento de Parasitologia, Facultad de Farmacia, Universidad de Valencia, Av. Vicent Andre´s Estelle´s s/n, 46100 Burjassot, Valencia, Spain ARTICLE INFO ABSTRACT Keywords: The capacity of climatic conditions to modulate the extent and intensity of parasitism is well Climate change known since long ago. Concerning helminths, among the numerous environmental Trematodiases modifications giving rise to changes in infections, climate variables appear as those Fascioliasis showing a greater influence, so that climate change may be expected to have an important Schistosomiasis Cercarial dermatitis impact on the diseases they cause. However, the confirmation of the impact of climate change on helminthiases has been reached very recently. Only shortly before, helminthiases were still noted as infectious diseases scarcely affected by climatechange, when compared to diseases caused by microorganisms in general (viruses, bacteriae, protozoans). The aim of the present paper is to review the impact of climate change on helminthiases transmitted by snails, invertebrates which are pronouncedly affected by meteorological factors, by focusing on trematodiases. First, the knowledge on the effects of climate change on trematodiases in general is reviewed, including aspects such as influence of temperature on cercarial output, cercarial production variability in trematode species, influences of magnitude of cercarial production and snail host size, cercarial quality, duration of cercarial production increase and host mortality, influence of latitude, and global-warming-induced impact of trematodes. Secondly, important zoonotic diseases such as fascioliasis, schistosomiasis and cercarial dermatitis are analysed from the point of view of their relationships with meteorological factors. Emphasis is given to data which indicate that climate change influences the characteristics of these trematodiases in concrete areas where these diseases are emerging in recent years. The present review shows that trematodes, similarly as other helminths presenting larval stages living freely in the environment and/or larval stages parasitic in invertebrates easily affected by climate change as arthropods and molluscs as intermediate hosts, may be largely more susceptible to climate change impact than those helminths in whose life cycle such phases are absent or reduced to a minimum. Although helminths also appear to be affected by climate change, their main difference with microparasites lies on the usually longer life cycles of helminths, with longer generation times, slower population growth rates and longer time period needed for the response in the definitive host to become evident. Consequently, after a pronounced climate change in a local area, modifications in helminth populations need more time to be obvious or detectable than modifications in microparasite populations. Similarly, the relation of changes in a helminthiasis with climatic factor changes, as extreme events elapsed relatively long time ago, may be overlooked if not concretely searched for. All indicates that this phenomenon has been the reason for previous analyses to conclude that helminthiases do not constitute priority targets in climate change impact studies. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +34 96 3544905; fax: +34 96 3544769. E-mail address: [email protected] (S. Mas-Coma). 0304-4017/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2009.03.024 Author's personal copy S. Mas-Coma et al. / Veterinary Parasitology 163 (2009) 264–280 265 Contents 1. Introduction . 265 2. Expected environmental changes and their effects on disease transmission . 266 2.1. Changes in key climate parameters. 266 2.2. Effects of climate changes on infectious diseases . 266 3. Climate change and helminthiases . 268 4. Effects of climate change on trematodiases . 268 4.1. Influence of temperature on cercarial output . 268 4.2. Cercarial production variability in trematodes . 269 4.3. Influences of magnitude of cercarial production, cercarial size and snail host size . 269 4.4. Cercarial quality . 270 4.5. Duration of cercarial production increase and host mortality . 270 4.6. Influence of latitude . 270 4.7. Global-warming-induced impact of trematodes . 270 5. Fascioliasis . 271 5.1. Environment, transmission and geographical distribution . 271 5.2. Climatics and fascioliasis forecast indices . 271 5.3. Remote sensing and geographic information systems . 272 5.4. Effects of climate change and global warming on fascioliasis . 272 6. Schistosomiasis . 273 6.1. Meteorological factors, snail hosts and transmission . 273 6.2. Modelling and mapping . 274 6.3. Climate change and schistosomiasis control. 274 7. Cercarial dermatitis . 275 7.1. Cold climate lakes and transmision. 275 7.2. Climate change and increase of summer outbreaks . 275 8. Concluding remarks. 276 Acknowledgements . 276 References . 277 1. Introduction (McCarthy et al., 2001). As early as 1990, the Intergovern- mental Panel on Climate Change (IPCC) had warned that Climate change and global warming are now accepted the climate change could affect the prevalence of vector- facts. Changes in air and sea surface temperatures, as well borne parasitic diseases (Houghton et al., 1990). as changes in precipitation, sea level, and ocean salinity The potential importance of parasites and pathogens as and circulation patterns, are predicted for the future. mediators of host population dynamics under changing Natural ecosystems will be impacted in one way or another climatic conditions in general and global warming in by these environmental changes. Climatic factors affect particular has been recently reviewed (Harvell et al., several ecological processes at different levels, from the 2002; Mouritsen and Poulin, 2002a). Any influence of performance of individual organisms, to the dynamics of climate on parasitism is potentially important for natural populations and community interactions, up to the communities and ecosystems. Many recent studies have distribution of species, because of the link between emphasized the causal relationship between climate change changes in ecosystem properties and functions with and parasitic diseases, whether emerging (new infections) large-scale climate fluctuations (Poulin and Mouritsen, or re-emerging (diseases rapidly increasing in either local 2006). The ecological consequences of climate change in prevalence and intensities or expanding their geographical terrestrial and marine ecosystems are expected to be distribution) (Harvell et al., 1999, 2002; Patz et al., 2000; determined by complex cascading effects arising from Marcogliese, 2001; Lafferty et al., 2004). In recent years, the modified trophic interactions and competitive relation- problem of emerging diseases has been a significant concern ships. The synergistic effect of climate change and (Molyneux, 2007). There is also evidence that climate can act parasitism on host population dynamics and community to synchronize cycles of host population abundance by structure has recently been emphasized (Mouritsen et al., directly affecting the survival and transmission of parasite 2005). infective stages (Cattadori et al., 2005). Thus, the many The capacity of climatic conditions to modulate the direct and indirect effects of temperature and other climatic extent and intensity of parasitism is well known since long variables on parasite transmission are bound to have ago. The development and transmission rates of parasitic community-wide impacts. For the interest of both human organisms are particularly sensitive to weather conditions. and domestic animal health, as well as of the preservation of The current climate change (global warming) will affect natural communities and ecosystems, it becomes crucial to the distribution and survival rate of parasite vectors and understand how parasites may respond to the climatic intermediate hosts and also directly influence the repro- changes expected in next decades, according to results duction and maturation rate of parasites carried by them obtained with forecasting climatic models. Author's personal copy 266 S. Mas-Coma et al. / Veterinary Parasitology 163 (2009) 264–280 Unfortunately, climate change overlaps other anthro- will occur. The regional distribution of this warming pogenic and environmental modifications (included in the shows the greatest amount of warming to be expected broad term of ‘global change’) which are able to give rise
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