TITLE:
A New Furunculosis Challenge Method for Evaluation of Vaccine Efficacy in Rainbow Trout
AUTHORS:
Moonika H. Marana, Jiwan K. Chettri, Jakob Skov, Inger Dalsgaard, Per W. Kania, Kurt Buchmann
KEYWORDS:
Aeromonas salmonicida, Challenge Method, Furunculosis, Immunization, Salmonids
JOURNAL NAME:
Open Journal of Immunology,
Vol.6 No.4,
November
28,
2016
ABSTRACT: Experimental infection of fish for vaccine efficacy studies is associated with several
limitations. Administration of live bacteria with the purpose of causing disease in
fish can be performed by co-habitation, immersion or injection. We have developed
a new Aeromonas salmonicida challenge method for rainbow trout and have applied
it for evaluation of furunculosis vaccine efficacy. The method reveals development of
systemic immunity in fish as live bacteria are introduced in the tail fin epidermis
distant from the vaccine injection site (peritoneal cavity). This method seeks to
mimic natural infection in fish farms where tail biting and therefore bacterial exposure
to tail fin ulcers is widespread. By use of a multi-needle device ten epidermal
perforations were introduced in the dorsal part of the tail fin of anaesthetized
rainbow trout (vaccinated or naive). Subsequently 100 μL (3.4 × 108 colony-forming
units (CFU) mL-1) of a 48 hour culture of Aeromonas salmonicida subsp. salmonicida strain 090710-1/23 was placed at the perforation site for 60 sec whereafter fish
were allowed to regain consciousness in clean freshwater. Immunohistochemistry
and scanning electron microscopy illustrated the spread of bacteria from the
injection site. Classical furunculosis symptoms associated with a high morbidity rate
were observed in control fish whereas vaccinated fish exhibited a significantly higher
survival.