Studies On Duckling With Riemerella Anatipestifer Infection In Hubei Province

There was an onset of duckling disease characterized by infectious serositis in some zones of Hubei province and outskirts of Wuhan city during recent two years. The disease was studied systematically including epidemic, pathology, clinical diagnosis and immune protective test. The investigation showed that Riemerella anatipestifer was the main responsible for death of 2 to 6 week-old ducklings. By taking pathological observation, infected ducklings were characterized by pericarditis, perihepatitis and all body septicemia. Riemerella anatipestifer was isolated easily from liver, spleen and blood, especially from brain. Two isolates were subjected to examine by biochemical, physiological, serological procedures. Drug sensitivity test were also performed with the two isolates. Results of both isolates were the same. They could not ferment glucose, maltose, fructose, lactose, mannose and produce H2S, urease, nitrate but can liquefacted gelatinase, to be peroxidase positive. The Yunmeng strain was highly susceptible to Norfloxacin, Furazolidone and Lincomycin; secondary susceptible to Ampicillin, Penicilin, Spectinomycin, Chloramphenicolum and Doxycycline; and not susceptible to Erythromycin and Bactracin. The Jiangxia strain was highly susceptible to Furazolidone, Bactracin, Lineomycin and Chloramphenicolum; secondary susceptible to Erythromycin, Norfloxacin, Spectinomycin and Doxycycline; and not susceptible to Ampicillin and Penicilin. Both strains belonged to serotype I of Riemerella anatipestifer by slide agglutination test. Immune protective test were conducted with three dose-group inactivated vaccines and one oil emulsion vaccine. Duckling at the age of 8 days was inoculated subentaneously at the neck with a dose of 0.5ml vaccine. Each vaccine group inoculated 70 ducklings. Control group is also 70 and added up to 350. The protective efficacy was good. All immunized groups can be protected against challenging with 2 LDso dose on the day 4, 7, 10, 14, 21, 28, 35 after immunization respectively. The protective effects of four vaccine groups were similar. The protective efficacy was produced at the fourth day and reached to the highest peak from the seventh to the tenth after vaccination, still remained 50% one month later, which showed these vaccines were rather effective at preventing from Riemerella anatipestifer infection.