Zebrafish (Danio rerio) are important models for biomedical research, and thus there is an increased concern about diseases afflicting them. Here we describe infections by Pleistophora hyphessobryconis (Microsporidia) in zebrafish from three laboratories. As reported in other aquarium fishes, affected zebrafish exhibited massive infections in the skeletal muscle, with no involvement of smooth or cardiac muscle. In addition, numerous spores within macrophages were observed in the visceral organs, including the ovaries. Transmission studies and ribosomal RNA (rRNA) gene sequence comparisons confirmed that the parasite from zebrafish was P. hyphessobryconis as described from neon tetra Paracheirodon innesi. Ten 15-day-old zebrafish were exposed to P. hyphessobryconis collected from one infected neon tetra, and 7 of 10 fish became infected. Comparison of P. hyphessobryconis small subunit rRNA gene sequence from neon tetra with that obtained from zebrafish was nearly identical, with < 1% difference. Given the severity of infections, P. hyphessobryconis should be added to the list of pathogens that should be avoided in zebrafish research facilities, and it would be prudent to not mix zebrafish used in research with other aquarium fishes.

The Zebrafish International Resource Center (ZIRC) is a repository and distribution center for mutant, transgenic, and wild-type zebrafish. In recent years annual imports of new zebrafish lines to ZIRC have increased tremendously. In addition, after 15 years of research, we have identified some of the most virulent pathogens affecting zebrafish that should be avoided in large production facilities, such as ZIRC. Therefore, while importing a high volume of new lines we prioritize safeguarding the health of our in-house fish colony. Here, we describe the biosecurity and health-monitoring program implemented at ZIRC. This strategy was designed to prevent introduction of new zebrafish pathogens, minimize pathogens already present in the facility, and ensure a healthy zebrafish colony for in-house uses and shipment to customers.

Pseudoloma neurophilia is a microsporidium of zebrafish (Danio rerio) that preferentially infects neural tissue. It is one of the most common pathogens of zebrafish in research laboratories based on diagnostic data from the Zebrafish International Resource Center diagnostic service (Eugene, OR). Five hundred fifty-nine zebrafish infected with P. neurophilia submitted to ZIRC from 86 laboratories between the years 2000 and 2013 were examined via histopathology to develop a retrospective study of the features of neural microsporidiosis. Parasite clusters (PCs) occurred in distinct axonal swellings, frequently with no associated inflammation. Inflammation was observed in viable cell bodies distant from PCs. Multiple PCs occasionally occurred within a single axon, suggesting axonal transport. PCs occurred most frequently in the spinal cord ventral white matter (40.3% of all PCs) and the spinal nerve roots (25.6%). Within the rhombencephalon, PCs were most common in the primary descending white matter tracts. Within the rhombencephalon gray matter, PCs occurred most frequently in the reticular formation and the griseum centrale (61% and 39%, respectively). High numbers of PCs within brain and spinal cord structures mediating startle responses and anxiety suggest that related behaviors could be altered by neural microsporidiosis. Infection could, therefore, introduce unacceptable variation in studies utilizing these behaviors.

Over the past several decades, a number of fish species, including the zebrafish, medaka, and platyfish/sword-tail, have become important models for human health and disease. Despite the increasing prevalence of these and other fish species in research, methods for health maintenance and the management of diseases in laboratory populations of these animals are underdeveloped. There is a growing realization that this trend must change, especially as the use of these species expands beyond developmental biology and more towards experimental applications where the presence of underlying disease may affect the physiology animals used in experiments and potentially compromise research results. Therefore, there is a critical need to develop, improve, and implement strategies for managing health and disease in aquatic research facilities. The purpose of this review is to report the proceedings of a workshop entitled “Animal Health and Disease Management in Research Animals” that was recently held at the 5th Aquatic Animal Models for Human Disease in September 2010 at Corvallis, Oregon to discuss the challenges involved with moving the field forward on this front.

Managing the welfare of laboratory animals is critical to animal health, vital in the understanding of phenotypes created by treatment or genetic alteration and ensures compliance of regulations. Part of an animal welfare assessment is the requirement to record observations, ensuring all those responsible for the animals are aware of their health status and can act accordingly. Although the use of zebrafish in research continues to increase, guidelines for conducting welfare assessments and the reporting of observations are considered unclear compared to mammalian species. To support the movement of zebrafish between facilities, significant improvement would be achieved through the use of standardized terms to ensure clarity and consistency between facilities. Improving the clarity of terminology around welfare not only addresses our ethical obligation but also supports the research goals and provides a searchable description of the phenotypes. A Collaboration between the Wellcome Trust Sanger Institute and Cambridge University (Department of Medicine-Laboratory of Molecular Biology) has led to the creation of the zebrafish welfare terms from which standardization of terminology can be achieved.