The Impact of Pseudoloma neurophilia Infection on Body Condition of Zebrafish.

The zebrafish is a widely used animal model in biomedical research. Despite this, pathogens continue to be common in laboratory zebrafish. It is important to determine and describe the pathophysiology of cryptic infections on zebrafish to elucidate the impacts on experimental endpoints. Body condition is a basic measurement used experimentally and in health monitoring of animals. We exposed three wild-type zebrafish strains: AB, WIK, and 5D to Pseudoloma neurophilia. After 8 weeks postexposure, we individually imaged and processed fish for histology. Morphometric analysis was performed on images and an index of body condition was calculated based on the ratio of length/width from the dorsal aspect. Histological sections from each fish were examined to establish sex, severity of infection, and tissue distribution. We observed a significant decrease in body condition in female fish that was not observed in males. In addition, we observed a negative correlation between the total gonadal area of P. neurophilia exposed females and unexposed controls. These results illustrate the sex-specific impacts of a common chronic pathogen on zebrafish health and a commonly used experimental endpoint, further supporting the establishment of rigorous health monitoring programs in laboratory zebrafish colonies that include screening for chronic infectious diseases.