Abstract
There are risks from disease in undertaking wild animal reintroduction programmes. Methods of disease risk analysis have been advocated to assess and mitigate these risks, and post-release health and disease surveillance can be used to assess the effectiveness of the disease risk analysis, but results for a reintroduction programme have not to date been recorded. We carried out a disease risk analysis for the reintroduction of pool frogs (Pelophylax lessonae) to England, using information gained from the literature and from diagnostic testing of Swedish pool frogs and native amphibians. Ranavirus and Batrachochytrium dendrobatidis were considered high-risk disease threats for pool frogs at the destination site. Quarantine was used to manage risks from disease due to these two agents at the reintroduction site: the quarantine barrier surrounded the reintroduced pool frogs. Post-release health surveillance was carried out through regular health examinations of amphibians in the field at the reintroduction site and collection and examination of dead amphibians. No significant health or disease problems were detected, but the detection rate of dead amphibians was very low. Methods to detect a higher proportion of dead reintroduced animals and closely related species are required to better assess the effects of reintroduction on health and disease.
Highlights
Reintroduction programmes undertaken for conservation purposes present a risk of disease to the reintroduced and recipient populations due to changes in the parasite complement of the reintroduced and recipient hosts, stressors on these animals and exposure to non-infectious disease agents (Sainsbury et al 2012)
A key objective of these disease risk analyses is to prevent the introduction of parasites alien to the reintroduction site (Sainsbury and Vaughan-Higgins 2012) because there is observed evidence that alien parasites, introduced through translocations, are associated with major epidemics of disease (Bobadilla et al 2016), for example squirrelpox virus introduced to the UK lead to catastrophic disease in red squirrels (Sainsbury et al 2008) and Sainsbury and Vaughan-Higgins (2012) assessed all infectious agents novel to the destination as hazards
In this paper we describe the disease risk analysis and post-release health surveillance undertaken for the reintroduction of the pool frog (Pelophylax lessonae) to the UK from Sweden, and evaluate the results
Summary
Reintroduction programmes undertaken for conservation purposes present a risk of disease to the reintroduced and recipient populations due to changes in the parasite (viral, bacterial, fungal, protozoal, helminth and ectoparasite) complement of the reintroduced and recipient hosts, stressors on these animals and exposure to non-infectious disease agents (Sainsbury et al 2012). For example reintroduction of Mallorcan midwife toads (Alytes muletensis) using captive-bred animals led to the introduction of the fungal pathogen (a pathogenic parasite) Batrachochytrium dendrobatidis to free-living populations (Walker et al 2008) and this pathogen has been associated with amphibian extinctions (Berger et al 1998); reintroduced cirl buntings (Emeriza cirlus) succumbed to stress-induced isosporosis (McGill et al 2010), and reintroduced Californian condors (Gymnogyps californianus) were threatened by toxins (Green et al 2008) Despite these hazards, reintroduction programmes continue to be considered important for conserving species (Ewen et al 2012) and translocations are expected to be increasingly used as conservation tools to counter the adverse effects of climate and other anthropogenic changes to the environment (McLachlan et al 2007; Hunter 2007). Monitoring the health of reintroduced and recipient populations following the reintroduction provides important information on the fate of animals, the reasons for the success or failure of the reintroduction and effectiveness of the disease risk analysis (Sainsbury et al 2012), and the need to monitor reintroduced populations rigorously and using standard methods has been advocated by Sutherland et al (2010)
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