Diseases of wild and farmed Finfish

Aeromonas salmonicida

Aeromonas salmonicida, the causative agent of the disease furunculosis, had a devastating impact on salmonid aquaculture up until the late 1980’s.  The disease induces septicaemia followed in chronic cases, by the appearance of boil like inflammatory lesions (or furuncles) and death. However, death also occurs in fish exhibiting no clinical signs. 

Little is known of how the airbourne pathogen is initially introduced to a fish farm however it is thought that healthy carrier fish entering a site may be responsible, although the disease can also transmitted via the waterbourne route.  The optimum temperature for A. salmonicida subsp salmonicida is 22ºC to 25ºC and furunculosis can occur when water temperatures exceed 16 ºC. 

There has been a significant amount of research carried out into the development of an effective vaccine for furunculosis.  Ellis AE (1994) developed a revolutionary vaccine in this marine laboratory which reduced catastrophic outbreaks of furunculosis to small isolated incidents.  Vaccines are still widely in use however antimicrobials are often used in tandem to eradicate the disease.

Diagnosis

• Bacteriological culture and biochemical testing
• Histopathology
• Molecular confirmation