| Duck viral hepatitis (DVH) caused by duck hepatitis virus-I is highly mortal disease and spread rapidly in ducklings. The ducklings infected DHV- I has high morbidity and mortality, and injecting vaccine is main method to prevent and control DVH at present. However, DHV still happens in ducks at times, and results in great damage to duck industry. If there is a way that can detect DVH antibody level simply and quickly, and also can apply in various research levels, and provide reference standard for DVH antibody detection, which will help the duck keepers to decrease their economic loss suffered by DVH. This research was conducted to optimize the DVH antibody latex agglutination test based on the method of our laboratory, and develop a method to detect DVH antibody in quantity. Besides, we can use it to observe the DVH antibody curve of breed ducks and ducklings, which can aslo help to make decision for the duck industry. The results followwed in detail:1. The virus was purified by Differential ultracentrifugation, and was done negative staining using phosphotungstic acid .Complete and lampros DVH- I virion was observed and indentified through electron microscope. Nucleic acid of several virion was not degradated yet, and diameter of virion was about 20-40nm, neucleocapsid was meristic icosahedron.2. The DHV- I antibody quantitative level was detected with the optimize DVH antibody latex agglutination test in clinic, and the DHV - I purified was allergized polystyrene latex. The detailed method is: the serum of ducks diluted multiple bind to the optimized latex, the titer of serum was the maximum deliquation that was seen some granulations.3. The DHV- I antibody quantitative level was detected with the optimize DVH antibody latex agglutination test in clinic, and the serum DHV- I antibody curve depend on time was obtained from the egg-ducks immunized with the weak DVH vaccine four times. The result showed: the antibody level of the second immunization and the fourth immunization kept much higher after 10 days coppared with ?, the titer was above 8; but rapidly decreased to 2 after 20 days in fourth immunization. Therefore, if we want to obtain egg yolk antibody, we need to immune the breed ducks several times, and also detect the antibody level in time.4. The DHV- I antibody quantitative level of the ducklings without maternal antibody was detected with the optimize DVH antibody latex agglutination test, and DHV- I antibody curve of ducklings without maternal antibody depend on time was obtained. The results showed: the antibody level of the ducklings without maternal antibody rised to peak value after seven days immunized with low virulent DHV- I vaccine, decreased a little after that, and the titer was about 5 after twenty days; however, the antibody level rised to peak value after three days immunized with egg yolk antibody, and decreased to about 5 after seven days. That's mean: compared with artificial active immunity and passive immunity, I found DHV- I vaccine was fit to be used in the nonage of ducklings, and DHV- I yolk antibody can be used to treat or emergency prevention.5. The DHV- I antibody quantitative level of the ducklings with maternal antibody was detected with the optimize DVH antibody latex agglutination test, and DHV - I antibody curve of ducklings with maternal antibody depend on time was obtained. The result indicated whatever immunized after 1 day or infected with high virulent DHV - I after immunization, the antibody of duckling with maternal antibody kept on decreasing, and was only about 4.5 after thirty days. Meanwhile, DHV- I vaccine was beneficial to increase the DHV- I level of ducklings rather than interfere the effect of maternal antibody. In addition, the protection of ducklings with maternal antibody should be 8 for latex agglutination value, it mean antibody dilution was 1:2~8. |
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