Comparative study on disease resistance and immune response to Aeromonas hydrophila of a hybrid of walking catfish (Clarias macrocephalus Gunther) and African catfish (Clarias gariepinus Burchell) and its parental species
1993
Boonkwang Karoon
Comparative study on disease resistance of a hybrid of walking catfish (Clarias macrocephalus Gunther) and African catfish (Clarias gariepinus Burchell) and its parental species by intraperitoneal injection of Aeromonas hydrophila revealed significant difference of LD50 values within 96 hours. Those values were 4.9*10*[7), 3.96*10*[7) and 8.6*10*[7) cells/ml respectively. Histopathological studies indicated similar findings in all experimentally infected fish. Liver cells were degenerated and focally necrotized. Anterior and posterior kidney were focally necrotized. Red and white pulp of spleen were focally necrotized and congested. There were inflammation in the epithelium and hemorrhage in serosa of intestine. Number of leucocytes were visibly increased in atrium and ventricle of the heart. Edema and hypertrophy were observed in gill lamellae. Comparative study on immune response to vaccine prepared from formalin-killed A. hydrophila by injection method was conducted. There were significant difference among the antibody titer for both primary and secondary immune response of all three kinds of fish with the average titer of 78.93, 401.07, 420.98, 614.40 and 460.80, 733.87 in catfish hybrid, walking catfish and African catfish respectively. Titer reached the peak in one week in catfish hybrid and two weeks in parental species after the first vaccination while the second vaccination induced the highest titer in two weeks after the vaccination in every kind of fish. All groups of vaccinated fish had significant protection over the controls after being challenged with virulent A. hydrophila with average survival rate of 97.78, 97.04 and 98.52 percents in catfish hybrid, walking catfish and African catfish respectively.
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