Development of an effective whole-spore vaccine to protect against microsporidial gill disease in rainbow trout (Oncorhynchus mykiss) by using a low-virulence strain of Loma salmonae.

In determining the effective vaccine spore dose of a low-virulence strain of Loma salmonae to limit microsporidial gill disease in trout, we found that fish receiving 10(3) to 10(5) killed spores had the best protection against experimental infection, with 85% fewer xenomas in their gills than in the controls. Intraperitoneal delivery of the vaccine was effective, and the addition of adjuvant did not improve vaccine performance against this disease-causing microsporidian.