ORIGINAL PAPER Trematode-associated morbidity and mortality of tadpoles in Israel L. Goren & J. Routtu & F. Ben-Ami Received: 19 June 2014 /Accepted: 23 July 2014 /Published online: 8 August 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Amphibians stand at the forefront of the global biodiversity crisis. The causes of their decline are diverse and include a rise in amphibian malformations due to various factors, especially trematode infection. However, linking am- phibian mortality and morbidity with trematode infection has proven to be challenging due to the complex life cycle of the trematodes and the fact that trematodes are nonfastidious in their choice of definitive hosts. In Israel, the decline in local amphibian populations has been mostly attributed to the loss and degradation of wetlands and riparian habitats. Recently, however, there have been several reports of morbidity and mortality of tadpoles with signs of edema and malformations from various localities in Israel. We collected dead and morbid tadpoles and metamorphs of Hyla savignyi and Pelophylax bedriagae, and we showed that the morbidity and the defor- mations observed in the field are the result of infection by trematodes. We also isolated an echinostomatid trematode from the malformed and edematous tadpoles and from the freshwater snail Bulinus truncatus, all from the same site. We further succeeded in experimentally infecting H. savignyi tad- poles by echinostomatid cercariae that were shed from the snails, and we showed that infection had significantly in- creased the mortality rates of these tadpoles. The combination of high trematode prevalence and their pathogenic effects suggests that in nature, the effect of echinostome infection on amphibians may be substantial and could become an emerging disease in Israel. Keywords Amphibian decline . Amphibian malformations . Bulinus truncatus . Echinostomatidae . Emerging diseases . Hyla savignyi . Pelophylax bedriagae Introduction Amphibians stand at the forefront of the global biodiversity crisis. With one third of all species in decline and more than 100 species extinct or suspected to be extinct in the last 25 years, amphibians are considered the most imperiled class of vertebrates worldwide (Houlahan et al. 2000; Stuart et al. 2004). The causes of such declines are diverse, including habitat loss, infectious disease, invasive species, and climate change, and may interact through complex mechanisms (Blaustein and Kiesecker 2002). Since the mid-1990s, am- phibian decline has been linked with a rise in amphibian malformations due to various factors, especially trematode infection (Blaustein and Johnson 2003). However, linking amphibian mortality and morbidity with trematode infection is often difficult due to the complex life cycle of the trema- todes and the fact that trematodes are nonfastidious in their choice of definitive hosts. For example, in most digenean species, only the adult worms have been described morpho- logically (Jousson et al. 1999), and it is often difficult to identify the intermediate host for larval stages of the parasite (Criscione et al. 2005). In Israel, six of the seven local amphibian species are endangered, and the decline in their populations has been mostly attributed to the loss and degradation of wetlands and riparian habitats (Gafny 2002). However, since the winter of 2011, there have been several reports of morbidity and mor- tality of tadpoles with signs of edema from various localities in Israel (Milstein 2011; Weissman et al. 2013). These reports have triggered an investigation into the causes of this morbid- ity with one main suspect: Ranavirus. However, no Ranavirus infection has been found in any of the cases investigated (Weissman 2013). Similar reports of malformations in the past were attributed to the effects of chemical pollutants (Dorchin 2007), but in these cases, there was no evidence of pollution and the causes of morbidity remained a mystery. L. Goren (*) : J. Routtu : F. Ben-Ami Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 6997801 Tel Aviv, Israel e-mail: goren.liron@gmail.com Parasitol Res (2014) 113:3833–3841 DOI 10.1007/s00436-014-4051-1