FELASA-AALAS Recommendations for Monitoring and Reporting of Laboratory Fish Diseases and Health Status, with an Emphasis on Zebrafish (Danio Rerio)

Abstract

The exchange of fish for research may expose an aquatic laboratory to pathogen contamination as incoming fish can introduce bacteria, fungi, parasites, and viruses capable of affecting both experimental results and fish and personnel health and welfare. To develop risk mitigation strategies, FELASA and AALAS established a joint working group to recommend good practices for health monitoring of laboratory fish. The recommendations address all fish species used for research, with a particular focus on zebrafish (Danio rerio). First, the background of the working group and key definitions are provided. Next, fish diseases of high impact are described. Third, recommendations are made for health monitoring of laboratory fishes. The recommendations emphasize the importance of daily observation of the fish and strategies to determine fish colony health status. Finally, report templates are proposed for historical screening data and aquatic facility description to facilitate biohazard risk assessment when exchanging fish.

Figure 1.

Index of disease descriptions in supplementary tables. This table helps readers to find information about diseases that are mentioned or described in Supplementary Tables S1 for zebrafish, S2 for other fish species, S3 in the context of a multispecies facility example, and in specific sections of the text. These supplementary materials are divided into smaller tables (A to G) referred to in the index. Although microsporidia are fungi or sister to fungi, they are commonly reported as parasites. They are therefore classified as parasites and included here in the fungus and parasite categories.

Figure 2.

Quarterly routine screening pattern for an epidemiologic unit. Histopathology can be performed on all euthanized and promptly fixed fish. Note that quarantine should not be part of the main epidemiologic unit, it is included here for convenience. In absence of fish that are imported or otherwise screened, sample the quarantine quarterly as appropriate (for example, sludge, sump surface swab; at least one sample type per quarter and per system).

Figure 3.

Use of nonlethal samples for pathogen detection. Nonlethal diagnostic examinations are performed mainly by microscopy (that is, fresh smear with or without staining) and stereomicroscopy. Some procedures obviously depend on fish dimensions. Y indicates that pathogens of the listed category are detectable in fresh smear, biopsies, or serology. Lesion biopsies can be used for histology, microbiologic cultures, and molecular biology tests for speciation. (1) indicates that only a few bacteria can be identified to their genus level in a fresh smear due to their unique characteristics (Flavobacteria spp., Tenacibaculum spp., Epitheliocytosis, Candidatus arthromitus) or after specific staining (for example, acid fast bacteria). Most bacteria must be identified by culture, bearing in mind the difficulties of aseptic sampling and bacteria isolation from skin and gills. (2) indicates that only lymphocystis can be diagnosed on fresh smear.