Abstract
Recently, a skin ulcerative disease caused by Vibrio mimicus has led to heavy economic losses in catfish, including yellow catfish, southern catfish, and Zhengchuan catfish in China. Currently, there was no effective method of controlling the outbreak of this disease. In this study, the bacterial isolates were obtained from dying channel catfish and identified as V. mimicus, which consist of formalin-inactivated V. mimicus (antigen). After first immunization, four weeks later, fishes were exposed to V. mimicus and the immune response was analyzed: Fish survival, respiratory burst activity of blood leukocytes, serum agglutination titers, and lysozyme activity, every week (during four weeks). Survival was up 90%. Respiratory burst activity of blood leukocytes, serum agglutination titers, and lysozyme activity were determined at 1, 2, 3, and 4 weeks after primary immunization. Immunization of channel catfish protected hosts against V. mimicus infection with a survival percentage of more than 90%. Respiratory burst activity of blood leukocytes was not affected by vaccination. Serum agglutination titer and lysozyme activity were significantly increased after immunization, in comparison with un-vaccinated control fish. The obtained results indicated that vaccination is an effective method to control the outbreaks of V. mimicus through regulation of the humoral immune response. Key words: Vibrio mimicus, catfish, skin ulcer, vaccine.
Highlights
Vibrio mimicus, a Gram-negative bacteria similar to Vibrio cholerae, has been identified as a causative agent of human gastroenteritis, which is characterized by watery to dysentery-like diarrhea (Davis et al, 1981; Takahashi et al, 2007)
Bacteria were isolated from the tissues of dying catfish, and the bacterial colonies were orbicular, smooth and white on blood agar, or green on TCBS agar (Figure 1B and C)
The phylogenetic analysis, based on the concatenated sequence of three housekeeping genes RNA polymerase α-chain (rpoA), recA, and pyrH, showed that the NH strain had a closer relationship to V. mimicus ATCC33653T than to V. cholerae CECT514T (Figure 2B)
Summary
A Gram-negative bacteria similar to Vibrio cholerae, has been identified as a causative agent of human gastroenteritis, which is characterized by watery to dysentery-like diarrhea (Davis et al, 1981; Takahashi et al, 2007). V. mimicus is a natural inhabitant of aquatic environments, including freshwater, brackish water, and saltwater. V. mimicus has been isolated from water samples (Adeleye et al, 2010; Chowdhury et al, 1989), sediments (Adeleye et al, 2010), aquatic plants (Li et al, 2005), snails (Li et al, 2005), oysters (Li et al, 2005), crayfish (Eaves and Ketterer, 1994), turtle eggs (Campos et al, 1996), shrimp
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