Detection of Asian Tapeworm Bothriocephalus acheilognathi Utilizing a Non-Lethal Molecular Screening Tool

The current standard for positive identification of fish Asian tapeworm Bothriocephalus acheilognathi infection is necropsy and visual examination of the gut via microscopy. While visual identification is considered the “gold” standard for positive identification of this parasite, the methodology is less than desirable for assessing parasitic infection in endangered fishes. The goal of this research is to determine whether swabbing for genetic material from the anogenital vent could replace terminal sampling of fishes to confirm B. acheilognathi infection. We examined the effects of swabbing fish via the anogenital pore through histological examination for tissue damage in captive Humpback Chub Gila cypha. From the swabs, we extracted DNA and amplified sequences of the ITS2 and the V4 regions of the B. acheilognathi 18S rRNA gene. A subsequent laboratory study quantified the sensitivity of the molecular methodology by exposing naïve (uninfected) larval Humpback Chub to B. acheilognathi. Sensitivity was calculated by cross-referencing positive infections identified via the lethal “gold” standard method with the molecular results from each corresponding anogenital swab. Successful development of a non-lethal molecular diagnostic tool will provide managers with a viable alternative to the current terminal standard for assessing infection in endangered hatchery and wild fish populations.