| Abstrakt: |
AbstractZebrafish (also known as zebra danio) Danio reriowere injected intramuscularly with Edwardsiella ictaluriat doses of 6 × 103, 6 × 104, or 6 × 105colony-forming units per gram (CFU/g) or sterile phosphate-buffered saline (sham) or were not injected. Mortality occurred from 2 to 5 d postinjection (dpi) at rates of 0, 76.6, and 81.3% for the low, medium, and high doses, respectively, and E. ictaluriwas isolated from dead fish. Survivors were sampled at 10 dpi and E. ictaluriwas not isolated. Sham-injected and noninjected controls did not suffer mortality. Histopathology trials were performed in which zebrafish were injected with 1 × 104CFU/g or sham-injected and sampled at 12, 24, 48, 72, and 96 h postinjection for histological interpretation. Collectively, these zebrafish demonstrated increasing severity of splenic, hepatic, cardiac, and renal interstitial necrosis over time. To evaluate the progression of chronic infection, zebrafish were injected with 1 × 102CFU/g and held for 1 month postinjection. Beginning at 12 dpi and continuing for an additional 2 weeks, zebrafish demonstrated abnormal spiraling and circling swimming behaviors. Histopathology demonstrated necrotizing encephalitis. In immersion trials, zebrafish were exposed to low, medium, and high doses (averaging 1.16 × 105, 1.16 × 106, and 1.16 × 107CFU/mL of tank water) of E. ictalurifor 2 h. Mortality occurred from 5 to 9 d postexposure at rates of 0, 3.3, and 13.3% for the low, medium, and high doses, respectively; E. ictaluriwas isolated from dead fish. Channel catfish Ictalurus punctatusexposed to the medium doses suffered 100% mortality, and E. ictaluriwas isolated from these fish. This study demonstrates the potential use of zebrafish as a model for E. ictaluripathogenesis. |
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