Application of ultrasound in vaccination against goldfish ulcer disease: a pilot study.

Antigenicity and immunogenicity of Aeromonas salmonicida soluble A-layer protein (AP) and formalin-killed bacterin were assessed in goldfish (Carassius auratus L.) by applying ultrasound-immersion (USI) and injection (Inj) routes. No adjuvant was used in USI while IFA was used in Inj. The USI treated fish did not produce detectable acquired antibodies; however, this group stimulated by AP proved to be best protected against challenge infection with a homologous virulent strain of A. salmonicida. The results reveal the asset of USI technique in fish vaccination and indicate the option of designing a pure AP-based ballast-free vaccine.