Serological identification of typical Aeromonas salmonicida

Aeromonas salmonicida subsp. salmonicida requires at least 48 h incubation to produce colonies suitable for morphological and biochemical identification and, as a result, diagnosis of furunculosis may take up to 1 week. This often represents an unacceptable time-lag for the fish farmer or veterinarian, who needs to make rapid decisions on the treatment and fate of infected fish. Rapid identification methods that could be applied directly to colonies after 48 h have the potential to overcome the...

Immunological detection techniques

Immunological detection techniques offer many advantages over culture-based techniques, particularly when attempting to detect organisms, such as A. salmonicida, whose growth on laboratory media can be inhibited by the presence of other bacteria. These techniques have been revolutionized in recent years by Table 10.8. Non-culture-based techniques developed for, or applied to, the detection of typical Aeromonas salmonicida since 1990. Table 10.8. Non-culture-based techniques developed for, or...

Genetic detection techniques

A second family of non-culture-based detection techniques that have been investigated for the detection of components of A. salmonicida is based on genetic principles. Typical A. salmonicida is homogeneous at the genetic level (vaughan, 1997) and presents, in theory, an ideal candidate for a genetic-based detection technique. Since 1990, a number of assays targeted against 16S ribosomal ribonucleic acid (rRNA) or DNA sequences of A. salmonicida have been developed for this organism (Table...

Treatments of covert infections

Hiney et al. (1997b) have presented a detailed review of the chemotherapeutic treatment of covert furunculosis infection. Fish with covert infections can, with good husbandry, be reared without any experience of overt disease (Scallan, 1983). Further, the presence of covert infections in a population are probably a reflection of the presence of A. salmonicida in their water-supply. Therefore, therapy of such covert infections is frequently neither justified nor liable, in the Table 10.9....

Vaccination

Vaccination strategies designed to control furunculosis were reported as early as the 1940s (Duff, 1941). Midtlyng (1997) has reviewed the attempts that were made, over the next 50 years, to produce vaccines and vaccine administration methods that would provide adequate control of this disease. Succinctly, and possibly rather unfairly, these attempts can be summarized, at least from the perspective of commercial salmon farmers, as failures. Oral, immersion and injection administrations of a...

Susceptibility to furunculosis

Most fish species would appear to be susceptible to infections by A. salmonicida, but the level of susceptibility is variable. For example, among salmonids, susceptibility to infection is reported to be low in rainbow trout (Cipriano and Heartwell, 1986 P rez et al., 1996), while brook trout, brown trout and many other salmon species appear to have a high susceptibility (McCraw, 1952 Evelyn, 1971 Klontz and Wood, 1972 Miyazaki and Kubota, 1975 McCarthy, 1977a Cipriano and Heartwell, 1986 Austin...

Limitation on the use of the stressinducible furunculosis test for detection of covert furunculosis infections

In Ireland, reliance on stress testing is widespread at the level of individual companies and has been successful, when used, in limiting the spread of furunculosis to marine farms (Smith, 1992 Scallan and Smith, 1993). Stress testing of salmon smolts prior to their transport to sea is a regulatory requirement in New Brunswick, Canada, and has also been found to be a successful measure there (Olivier, 1992). However, although stress testing is valuable in the field, it is not without its...

Covert infection by typical Aeromonas salmonicida

The existence of covert furunculosis, that is, clinically unapparent infections, has been recognized almost as long as the disease itself (Plehn, 1911). The epizootiological importance of fish with covert furunculosis in the maintenance and spread of the disease within and between susceptible fish populations was understood by early workers. In 1935 the Scottish Furunculosis Committee concluded that clinically unapparent infections by A. salmonicida could persist in fish populations, that these...