Bacterial pathogens are a major cause of infectious diseases and mortality in wild fish stocks and fish reared in confined conditions. Disease problems constitute the largest single cause of economic losses in aquaculture . Concurrent with the rapid growth and intensification of aquaculture, increased use of water bodies, pollution, globalization, and transboundary movement of aquatic fauna, the list of new pathogenic bacterial species isolated from fish has been steadily increasing . In addition, the virulence and host range of existing pathogens has also been increasing, posing considerable challenge to fish health researchers, who are actively looking for more efficient vaccines and therapeutic drugs to combat bacterial fish diseases. The current treatment methods are ineffective and have many practical difficulties.
Review of Bacterial Diseases of Aquarium Fish - IAAAM_Archive - VIN
There has been a significant change in understanding of fish diseases caused by an organism historically identified as . This organism is the causative agent of emphasematous putrifactive disease of catfish. The name is descriptive of the most common lesions, an ulcerative dermatitis associated with a malodorous, gas-producing bacteria. is an enteric bacterium that is ubiquitous in terrestrial and aquatic environments. It has been associated with enteric disease in mammals, including people, as well as birds, reptiles, and fish. Recent molecular work has demonstrated that several different organisms that may have been previously identified as are likely causing many of the disease outbreaks attributed to in fish. These newly recognized taxa, and –like organisms, are considered important emerging diseases in the channel catfish industry. They can present not only as an ulcerative dermatitis but also can cause a systemic granulomatous disease with gross and microscopic lesions very similar to those seen in mycobacteriosis (see ). Granulomatous disease attributed to tends to result in hepatic lesions, which are not typical of mycobacteriosis. Histologically, the granulomas contain gram-negative and acid-fast negative rods. Molecular testing is required to confirm a diagnosis of or –like infection. The disease will respond to antibiotics, but it is unclear whether fish can clear bacteria sequestered in granulomas. These environmental bacteria thrive in organically rich environments, so sanitation may need to be addressed as part of the management strategy. For aquariums and recirculating systems, UV filtration may help decrease numbers of bacteria in the environment.
Bacterial diseases can be a cause of high mortality in aquarium fish
causes enteric septicemia of catfish, the most important infectious disease in the channel catfish industry. Infection occurs in the spring and fall when water temperatures are 22°–28°C, and mortality may be exacerbated by handling stress, chemical treatment, or poor water quality. The disease occurs in two forms: the enteric (or intestinal) form and the meningeal form. In the enteric form, infected fish may develop skin lesions characterized by massive petechial hemorrhage around the mouth, operculum, and eyes, or they may develop measles-like, red, punctate lesions along the body wall. There is a hemorrhagic enteritis, and the intestine may be hemorrhagic and fluid- or gas-filled. Liver lesions are common and may be evident as multifocal areas of necrosis, abcessation, or hemorrhage. In contrast, in the meningeal form, few external signs may be seen in infected fish. The bacteria enter the CNS through the olfactory system, and affected fish develop severe meningitis. In fingerlings, the inflammation may be severe enough to erode the skull, resulting in the characteristic “hole-in-the-head” lesion. Fish affected with the meningeal form may demonstrate bizarre behavior, including spinning, erratic swimming, and general disorientation. Diagnosis is based on bacterial culture and isolation. Brain culture is indicated whenever is suspected. will grow on blood agar incubated at 25°C for 48 hr. Antibiotic therapy should be based on results of sensitivity testing. Vaccination is available for channel catfish fingerlings.
Bacterial Kidney Disease (BKD) | Disease guide | The Fish Site