A Multi-Site Assessment of Anesthetic Overdose, Hypothermic Shock, and Electrical Stunning as Methods of Euthanasia for Zebrafish (Danio rerio) Embryos and Larvae

Current Status of the Zebrafish Euthanasia and Humane Endpoint in the Republic of Korea and Guideline Suggestion from Nationwide Expert Elicitation: A Model for Other Countries

Since its introduction as a model organism in the 1980s, the use of zebrafish (Danio rerio) in research has expanded worldwide. Despite its now widespread use in research, guidelines to safeguard the ethical treatment of zebrafish, particularly with regard to euthanasia and humane endpoint practices, remain inadequate. One well-recognized example is the use of excess tricaine methanesulfonate (MS-222) as a means to euthanize zebrafish, regardless of life stage. In this study, through nationwide expert elicitation, we provide a detailed account of zebrafish research practices within the Republic of Korea and the challenges of implementing appropriate methods for euthanasia as a humane endpoint, with many opting for hypothermic shock. We report a local expert consensus for establishing national guidelines to improve zebrafish welfare and good research practice. Suggestions and recommendations for national guidelines were offered. Taken together, our findings raise awareness broadly among zebrafish research practitioners in the field, offer an accurate account of the welfare and treatment of zebrafish in research within the Republic of Korea, and advocate for the development and implementation of national guidelines. As such, our study is useful as a model to adopt the expert elicitation approach to investigate, quantify, and address welfare concerns in zebrafish research, and to establish best practice guidelines.

A FELASA Working Group Survey on Fish Species Used for Research, Methods of Euthanasia, Health Monitoring, and Biosecurity in Europe, North America, and Oceania

Simple Summary

An international survey was conducted regarding species used for research, methods of euthanasia, health monitoring, and biosecurity in fish laboratories. A total of 145 facilities from 23 countries contributed. Over 80 different species were reported to be used for research, of which zebrafish (Danio rerio) was the most common by far. Anesthetic overdose was the preferred method for euthanasia for adults, fry, and larvae not capable of independent feeding. For all developmental stages, the most popular anesthetic compound was tricaine. Around half of the respondents did not perform a completion method to ensure death. One-quarter of the responding facilities did not have a health monitoring system in place. Only a small fraction reported quarantine routines to ensure reliable biological barriers. There was little consensus amongst facilities in how to perform biosecurity measures.

Abstract

An international survey was conducted regarding species used for research, methods of euthanasia, health monitoring, and biosecurity in fish laboratories. A total of 145 facilities from 23 countries contributed. Collectively, over 80 different species (or groups of species) were reported to be used for research, of which zebrafish (Danio rerio) was the most common by far. About half of the participating laboratories used multiple species. Anesthetic overdose was the preferred method for euthanasia for adult, fry (capable of independent feeding), and larval (not capable of independent feeding) fish. For all developmental stages, the most popular anesthetic compound was tricaine (MS-222), a substance associated with distress and aversion in several species. Moreover, around half of the respondents did not perform a completion method to ensure death. One-quarter of the responding facilities did not have a health monitoring system in place. While most respondents had some form of quarantine process for imported fish, only a small fraction reported quarantine routines that ensure reliable biological barriers. Furthermore, less than one in five screened fish for pathogens while in quarantine. In sum, there was little consensus amongst facilities in how to perform biosecurity measures. Regarding euthanasia, health monitoring, and biosecurity processes, there is a need for updated and universal guidelines and for many laboratories to adjust their practices.