3 - Covert Aeromonas salmonicida Infections

Abstract

The existence of clinically inapparent Aeromonas salmonicida infections has been recognized almost as long as the disease itself. Clinically inapparent infections were common and could persist in populations of fish for periods of months. These infections could be latent. If infected fish populations were stressed, overt clinical furunculosis could be precipitated. Fish with these infections were capable of acting as carriers. They could shed sufficient bacteria to transmit the infection to other fish. Fish with these clinically inapparent infections played a major role in the epizootiology of furunculosis. A variety of methods, of differing efficiency, that have been employed to detect these infections are discussed in this chapter. The covert infections are classified into three categories: incubatory clinical infections, subclinical infections, and commensal infections. These infections are persistent in nature and play a central role in the spread of the disease. Covert infections are the key to understanding the epizootiology of overt furunculosis.