Development of a novel assay for the characterization of germination responses in microsporidian parasites: An investigation into the biology of Spraguea americanus

Abstract

The microsporidia are a widespread group of intracellular parasites which infect a broad range of hosts across the animal kingdom. In particular, the microsporidian Spraguea americanus has received considerable attention in recent years due to its role as an endemic pathogen in American anglerfish (Lophius americanus); a species of highly valued finfish currently at risk due to overfishing. However, like many species of microsporidia, the germination responses of S. americanus remain poorly described. This study outlines a novel in vitro germination assay for microsporidia, which is then used to comprehensively survey the germination responses of S. americanus under a variety of conditions. The results of this investigation indicate that S. americanus is responsive to mechanical pressure, hydrogen peroxide, sodium carbonate/bicarbonate and divalent cations, but not to mucin proteins as seen in closely related species. These observations provide evidence to refute the predominant hypothesis that members of Spraguea enter their hosts via the subcutaneous mucosal glands. In addition to providing much needed insight into the transmission of Spraguea spp., this study is among the first to extensively assess the germination responses of a single species of microsporidia; data which may lend itself to a more complete understanding of the mechanisms underlying the initiation of germination in microsporidia or support the establishment of new in vitro models for economically relevant species.