Introduction

Aeromonas salmonicida has been recognized as a pathogen of fish for over 100 years. Emmerich and Weibel (1894) made the first authentic report of its isolation during a disease outbreak at a Bavarian brown trout hatchery, the manifestations of the disease including furuncle-like swelling and, at a later stage, ulcerative lesions on infected trout. Since that time a number of subspecies of A. salmonicida have been recognized, although the taxonomy of the species is far from settled. Aeromonas salmonicida is one of the most studied fish pathogens, because of its widespread distribution, diverse host range and economically devastating impact on cultivated fish, particularly the salmonids.

While Aeromonas salmonicida was traditionally thought of as a pathogen of salmonids, global reports now confirm that this pathogen has been associated with clinical or covert disease in a variety of salmonid and non-salmonid species in freshwater, brackish water and sea water.

Epidemiology

The geographical distribution of A. salmonicida subsp. salmonicida is almost worldwide, including Japan and the mainland of Asia. The possible exceptions to this distribution are South America and New Zealand, from which reports of the isolation of A. salmonicida have yet to be made. To date, there have been no reports of 'typical' furunculosis in salmonids in Australia, despite many attempts to isolate the organism (Bernoth, 1997a). Atypical A. salmonicida was, however,
identified from diseased goldfish in South Africa.

© CAB INTERNATIONAL 1999. Fish Diseases and Disorders, Volume 3: Viral, Bacterial and Fungal Infections(eds P.T.K. Woo and D.W. Bruno)