The Investigation On The Riemerella Anatipestifer Infections In Commercial Meat-Type Ducks In Some Areas Of Guangxi

Riemerella anatipestifer (RA) infection is a contagious disease of ducks. Ducklings of 1-7 wk of age are highly susceptible. It occurs as an acute or chronic septicemia characterized by fibrinous pericarditis, perihepatitis, and airsacculitis. RA infection accounts for major economic losses to the duck industry due to high mortality, weight loss. RA has many serotypes, and each serotype has not protection function with others. Resistance strains would appear easily after using antibiotics frequently for the ducks infected RA. A comprehensive study on the disease in Guangxi is essential for its effective control.184 diseased or death ducks with serositis collected from 29 commercial flocks of meat-type ducks in Nanning, Rongxian and Qinzhou were used as the samples for the isolation and identification of RA. Colonies grown on chocolate agar in candle jar from the samples were 0.5～2mm in diameter, entire, convex, transparent, but not colonies grown on MacConkey agar. The cultures were gram-negative, rod occurring singly, in pairs, and occasionally in chains. Many cells stained bipolar with Wright's stain. Biochemical identification of 82 isolates was performed and the results showed that all of isolates were consistent with the RA reference strain NN050021①. Serotyping of all the isolates were done by slide agglutination test and the results showed that all of isolates had positive reaction to the antiserum which were prepared by a RA reference strain of serotype 2. All of isolates were also tested by a PCR technique for the amplification of the 42kD outer membrane gene and a specific 809bp fragment were amplified from all of isolates, but not from Escherichia Coli (E. coli) and Pasteurella multocida isolated from ducks. 24 representative isolates were used for the antibacterial sensitivity test with the 12 kinds of common antibiotics and the results showed that most of the RA isolates were highly sensitive to Cefazolin, Cefradine, and Cefoperazone, but resistance to Enrofloxacin, Lomefloxacin, Ciprofloxacin, Doxycycline, and Kanamycin. E. coli were...