Progression of infection and detection of Pseudoloma neurophilia in zebrafish Danio rerio Hamilton by PCR and histology

Abstract

Pseudoloma neurophilia is a critical threat to the zebrafish ( Danio rerio ) model, as it is the most common infectious agent found in research facilities. In this study, our objectives were two‐fold: (1) compare the application of diagnostic tools for P. neurophilia and (2) track the progression of infection using PCR and histology. The first experiment showed that whole‐body analysis by qPCR (WB‐qPCR) can be a standardized process, providing a streamlined diagnostic protocol, without the need for extraction of specific tissues. Evaluating the course of infection in experimentally infected fish, we showed key dynamics in infection. Starting with a low dose exposure of 8000 spores/fish, the prevalence remained low until 92 days post‐exposure (dpe), followed by a 30%–40% prevalence by histology or 40%–90% by PCR until the end of the experiment at 334 dpe. WB‐qPCR positively detected infection in more fish than histology throughout the study, as WB‐qPCR detected the parasite as early as 4 dpe, whereas it was undetected by histology until 92 dpe. We also added a second slide for histologic analyses, showing an increase in detection rate from 24% to 26% when we combined all data from our experiments, but this increase was not statistically significant.

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