Council Directive 92/66/EECShow full title

CHAPTER 3 U.K. Differential diagnosis

1. Preliminary differentiation U.K.

It is intended that all haemagglutinating viruses should be submitted to the national laboratory referred to in Annex II for full identification, characterization and pathogenicity tests. However, it is important that interim control measures for Newcastle disease aimed at limiting the spread of the virus should be implemented as soon as possible and regional laboratories should be able to identify the presence of Newcastle disease virus. The haemagglutinating fluids should, therefore, be used in an haemagglutination inhibition test as described in Chapters 5 and 6. Positive inhibition 1. e. 2⁴, or more, with the Newcastle disease virus specific polyclonal antiserum of titre known to be at least 2⁹ would serve as preliminary identification enabling the imposition of interim control measures.

2. Confirmatory identification U.K.

The national laboratory should undertake full differential diagnosis of any haemagglutinating agent. Confirmation of Newcastle-disease virus would again be by inhibition in haemagglutination inhibition tests with monospecific chicken antisera. Intracerebral pathogenicity index tests as described in Chapter 7 should be carried out on all positive isolates. Pathogenicity indices of greater than 0,7 indicate the presence of virus requiring the full implementation of control measures.

Recent developments in typing Newcastle-disease viruses, particularly monoclonal antibody techniques, has enabled grouping of the strains and isolates. In particular, some monoclonal antibodies are available which are specific for the vaccinal strains used on the territory of the Community and can be employed in simple haemagglutination inhibition tests.

Since live vaccine strains may often be isolated from sampled poultry the advantage of their rapid identification at the national laboratory referred to in Annex II is obvious. Such monoclonal antibodies should be obtained by the Community reference laboratory as referred to in Article 14 and supplied to the national laboratories to enable confirmation of the isolation of vaccinal viruses.

The national laboratories should submit all haemagglutinating agents to the Community reference laboratory.

3. Further typing and characterization of isolates U.K.

The Community reference laboratory should receive all haemagglutinating viruses from the national laboratories for further antigenic and genetic studies to enable a greater understanding of the epizootiology of the disease(s) within the Community in keeping with the functions and duties of the reference laboratory.