Fish Asian Tapeworm in an Endangered Southwestern Fish: Assessing Infections Using a Non-lethal Molecular Screening Tool

Authors: Meredith Campbell, Colleen A. Caldwell, Wade Wilson, Teresa D. Lewis

Year: 2016 (xlviii)

Abstract

The current standard for positive identification of fish Asian tapeworm Schyzocotyle acheilognathi infection is necropsy and visual examination of the gut via microscopy, a method which is not ideal for assessing parasitic infection in endangered fish. This research aimed to determine whether collecting anogenital swabs for genetic material could replace terminal sampling of fish. An experiment was conducted in which infected captive Humpback Chub Gila cypha were swabbed and necropsied to assess presence/absence of infection. DNA was extracted from the swabs, and PCR was used to amplify S. acheilognathi COXI mtDNA. Mean primer set sensitivity was 52% percent while mean specificity was 79% percent. Even with moderately-low sensitivity, the non-lethality of this methodology may offset decreased sensitivity, especially for rare fish. Sequencing revealed that the modera te specificity is a result of the primer detecting residual environmental DNA, not decreased species fidelity. Primer sensiti vity may be a function of the swabbing process and parasite developmental stage. Swabs were collected from wild populations of Humpback Chub for S. acheilognathi and revealed average infection prevalence of 13%, and relative infection frequency of 6.6 - 21.4%. This non-lethal molecular diagnostic tool will provide managers with a viable alternative to the current terminal standard for assessi ng infection and quantifying prevalence in endangered hatchery and wild fish populations.