Climate change effects on trematodiases, with emphasis on zoonotic fascioliasis and schistosomiasis

• Published in: Veterinary parasitology 2009-08, Vol.163 (4), p.264-280
• Main Authors: Mas-Coma, Santiago, Valero, Maria Adela, Bargues, Maria Dolores
• Format: Article
• Language: English
• Subjects: Animals; Animals, Domestic; Animals, Wild; Arthropoda; Cercarial dermatitis; Climate Change; Disease Reservoirs - parasitology; Disease Reservoirs - veterinary; Fasciola; Fascioliasis; Fascioliasis - epidemiology; Fascioliasis - parasitology; Fascioliasis - transmission; Fascioliasis - veterinary; helminthiasis; helminths; Host-Parasite Interactions; host-pathogen relationships; intermediate hosts; literature reviews; Mollusca; Oocysts; Prevalence; Schistosoma; Schistosomiasis; Schistosomiasis - epidemiology; Schistosomiasis - parasitology; Schistosomiasis - transmission; Schistosomiasis - veterinary; Seasons; snails; Snails - parasitology; Trematoda; trematode infections; Trematodiases; Zoonoses
• ISSN: 0304-4017; 1873-2550
• DOI: 10.1016/j.vetpar.2009.03.024

The capacity of climatic conditions to modulate the extent and intensity of parasitism is well known since long ago. Concerning helminths, among the numerous environmental modifications giving rise to changes in infections, climate variables appear as those showing a greater influence, so that climate change may be expected to have an important 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 climate change, 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 lo