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ARS Home » Research » Publications at this Location » Publication #65338


item GELB,JR., J.
item King, Daniel
item WISNER, W.
item RUGGERI, P.

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Respiratory diseases of chickens are a major cause of economic loss. Infections with Newcastle disease virus (NDV) or infectious bronchitis virus (IBV) are among the most important causes of respiratory disease and produce loss in the form of reduced rate of weight gain, condemnations at processing, and mortality. Bacterial infections that are more easily established in the respiratory tract after a viral infection add to the severity. On occasion the live virus vaccines used widely to prevent Newcastle disease and infectious bronchitis can cause as much damage as the field strains of virus. Serial passage of an NDV vaccine in embryonated eggs incubated at a reduced temperature produced a modified NDV vaccine called Ca-B1 that had acquired a property of substantially reduced growth at the normal body temperature of the chicken. Further, Ca- B1 caused much less respiratory disease than the parent vaccine virus in inoculated chickens and the chickens vaccinated with the virus were protected against a virulent NDV challenge. Ca-B1 used alone has the highly desirable properties of providing effective protection with reduced potential for causing respiratory disease. Unfortunately, Ca-B1 was found to be ineffective when given with IBV vaccine, the most common method of administering those vaccines.

Technical Abstract: The B1 strain of NDV was cloned and serially passaged in specific- pathogen-free (SPF) chicken embryos incubated at two temperatures. Virus passaged at 29C was called cold-adapted (Ca) and 37C passages were designated non-cold-adapted (non-Ca). The Ca and non-Ca B1 viruses were compared with the parent B1 and a commercial B1 vaccine. In vitro Ca B1 characteristics are a more rapid growth at 29C and a reduced growth at 41C, properties not seen with non-Ca B1. Embryo mean death times for the Ca virus were longer than for non-Ca B1 and parent B1 viruses. The Ca virus retained a rapid hemagglutination elution rate but lost the property of binding the monoclonal antibody AVS-I typical of other B1 strains. The pathogenicity of the Ca B1 strain was compared to the non-Ca B1, parent B1, and a commercial B1 strain vaccine in 1-day-old broiler chicks. Pathogenicity was evaluated by daily observation to assess the severity of f respiratory disease signs and to determine the incidence of airsacculitis perihepatitis, and pericarditis for calculation of a respiratory disease index. The Ca B1 strain had a lower respiratory disease index and a much lower incidence of air sac lesions which indicated it was less pathogenic than all the other strains. Immunogenicity tests in 1-wk-old SPF leghorns indicated Ca B1 induced complete protection when administered alone but only partial protection when it was given in combination with IBV.