Phylogenetic and environmental DNA insights into emerging aquatic parasites: implications for risk management

Salma Sana,Chris Williams,Emilie A Hardouin,Adrian Blake,Phil Davison,Josie Pegg,Richard Paley,Tiantian Zhang,Demetra Andreou

doi:10.1016/j.ijpara.2017.11.002

Abstract

Species translocation leads to disease emergence in native species of considerable economic importance. Generalist parasites are more likely to be transported, become established and infect new hosts, thus their risk needs to be evaluated. Freshwater systems are particularly at risk from parasite introductions due to the frequency of fish movements, lack of international legislative controls for non-listed pathogens and inherent difficulties with monitoring disease introductions in wild fish populations. Here we used one of the world’s most invasive freshwater fish, the topmouth gudgeon, Pseudorasbora parva, to demonstrate the risk posed by an emergent generalist parasite, Sphaerothecum destruens. Pseudorasbora parva has spread to 32 countries from its native range in China through the aquaculture trade and has introduced S. destruens to at least five of these. We systematically investigated the spread of S. destruens through Great Britain and its establishment in native fish communities through a combination of phylogenetic studies of the host and parasite and a novel environmental DNA detection assay. Molecular approaches confirmed that S. destruens is present in 50% of the P. parva communities tested and was also detected in resident native fish communities but in the absence of notable histopathological changes. We identified specific P. parva haplotypes associated with S. destruens and evaluated the risk of disease emergence from this cryptic fish parasite. We provide a framework that can be applied to any aquatic pathogen to enhance detection and help mitigate future disease risks in wild fish populations.

Highlights

Species translocation leads to disease emergence of considerable ecological and economic importance (Fisher et al, 2012)
The third S. destruens-positive P. parva population was from Site 1a which represented the first accidental P. parva introduction into Great Britain (GB) in the 1980s and tested positive for S. destruens with a prevalence of 3% (Fig. 1)
Generalist parasites are more likely to be transported and establish in new communities, and here we show that the nonnative parasite S. destruens has been transported to multiple locations in GB and has potentially spread to adjacent native fish communities

Summary

Introduction

Species translocation leads to disease emergence of considerable ecological and economic importance (Fisher et al, 2012). Freshwater systems are at risk due to insufficient international legislation and system-inherent disease monitoring difficulties (Gozlan, 2012). This has resulted in the frequent introduction of non-native parasites to freshwater fisheries (Williams et al, 2013) with a risk of aquatic disease emerq Note: Nucleotide sequence data reported in this paper are available in the GenBankTM database under the accession numbers MG283239-MG283252, MG386173-MG386179. The topmouth gudgeon, Pseudorasbora parva, is a small cyprinid fish that is naturally distributed in eastern Asia It was introduced into Europe from China in the 1960s through a succession of accidental introductions into the area around the Black Sea through the trade of Chinese carp in aquaculture (Gozlan et al, 2010). In 2005, P. parva was identified as a healthy reservoir of the generalist parasite Sphaerothecum destruens which has been identified as a threat to freshwater fish biodiversity (Gozlan et al, 2005)

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Results

Conclusion