Development of the microsporidian parasite, Loma salmonae, in a rainbow trout gill epithelial cell line (RTG-1): evidence of xenoma development in vitro

SUMMARYGrowth and propagation of fish-infecting microsporidians within cell culture has been more difficult to achieve than for insect- and human-infecting microsporidians. Fish microsporidia tend to elicit xenoma development rather than diffuse growth in vivo, and this process likely increases host specificity. We present evidence that the fish microsporidian, Loma salmonae, has the capacity to develop xenomas within a rainbow trout gill epithelial cell line (RTG-1). Spore numbers increased over a 4 weeks period within cell culture flasks. Xenoma-like structures were observed using phase contrast microscopy, and then confirmed using transmission electron microscopy. Optimization of the L. salmonae-RTG-1 cell model has important implications in elucidating the process of xenoma development induced by microsporidian parasites.

Demonstrated Efficacy of a Pilot Heterologous Whole-Spore Vaccine against Microsporidial Gill Disease in Rainbow Trout

ABSTRACTIntraperitoneal vaccines using whole viable spores of the microsporidianGlugea anomalaorGlugea hertwigireduced the numbers of branchial xenomas by 80% and 91%, respectively, after a standard experimental infection of juvenile rainbow trout with the microsporidianLoma salmonae. Similar significant results were obtained when killed-spore preparations were used.

Impact and control of protozoan parasites in maricultured fishes

SUMMARYAquaculture, including both freshwater and marine production, has on a world scale exhibited one of the highest growth rates within animal protein production during recent decades and is expected to expand further at the same rate within the next 10 years. Control of diseases is one of the most prominent challenges if this production goal is to be reached. Apart from viral, bacterial, fungal and metazoan infections it has been documented that protozoan parasites affect health and welfare and thereby production of fish in marine aquaculture. Representatives within the main protozoan groups such as amoebae, dinoflagellates, kinetoplastid flagellates, diplomonadid flagellates, apicomplexans, microsporidians and ciliates have been shown to cause severe morbidity and mortality among farmed fish. Well studied examples are Neoparamoeba perurans, Amyloodinium ocellatum, Spironucleus salmonicida, Ichthyobodo necator, Cryptobia salmositica, Loma salmonae, Cryptocaryon irritans, Miamiensis avidus and Trichodina jadranica. The present report provides details on the parasites’ biology and impact on productivity and evaluates tools for diagnosis, control and management. Special emphasis is placed on antiprotozoan immune responses in fish and a strategy for development of vaccines is presented.