Viral diseases in zebrafish: what is known and unknown

Naturally occurring viral infections have the potential to introduce confounding variability that leads to invalid and misinterpreted data. Whereas the viral diseases of research rodents are well characterized and closely monitored, no naturally occurring viral infections have been characterized for the laboratory zebrafish (Danio rerio), an increasingly important biomedical research model. Despite the ignorance about naturally occurring zebrafish viruses, zebrafish models are rapidly expanding in areas of biomedical research where the confounding effects of unknown infectious agents present a serious concern. In addition, many zebrafish research colonies remain linked to the ornamental (pet) zebrafish trade, which can contribute to the introduction of new pathogens into research colonies, whereas mice used for research are purpose bred, with no introduction of new mice from the pet industry. Identification, characterization, and monitoring of naturally occurring viruses in zebrafish are crucial to the improvement of zebrafish health, the reduction of unwanted variability, and the continued development of the zebrafish as a model organism. This article addresses the importance of identifying and characterizing the viral diseases of zebrafish as the scope of zebrafish models expands into new research areas and also briefly addresses zebrafish susceptibility to experimental viral infection and the utility of the zebrafish as an infection and immunology model.