Project Summary/Abstract The use of zebrafish (Danio rerio) as part of an integrative approach to improving human health is now second to mice in vertebrate models, with over 900 NIH grants using the model. Certain pathogens are very common in zebrafish facilities. The three most common diseases/infections of zebrafish in research laboratories are microsporidiosis, caused by Pseudoloma neurophilia, mycobacteriosis (caused by multiple species of Mycobacterium), and parasitic enteritis (caused by the nematode Pseudocapillaria tomentosa). For example, Pseudoloma occurs infects zebrafish in about half of the research facilities. This project will continue to develop methods of control or avoid these pathogens. We will also continue to elucidate the effects of these infections on research endpoints, as they may be important causes of non-protocol variation – e.g., Pseudoloma alters the behavior of otherwise clinically normal zebrafish. Our studies will include investigations on effects of infections on cytokine rDNA expression and intestinal microbiome profiles, and inter-strain variability in pathogenesis and microbiomes between popular outbred strains of zebrafish. We will continue to develop efficacious antibiotics M. chelonae infections, and will develop non-lethal PCR based tests for Pseudoloma, Pseudocapillaria and Mycobacterium marinum.