GB/T 16550-2020 in English

Background of Standard Revision and Technological Evolution

GB/T 16550-2020, as the national standard for Newcastle disease diagnosis, has achieved three major technological breakthroughs after replacing the 2008 version:

Core diagnostic technical specifications

1. Virus isolation and ICPI determination

When using SPF chicken embryos for virus isolation, please note:

• Time for harvesting allantoic fluid: 18h to 96h after inoculation
• Blind transmission requirement: The first generation HA titer <3log2 needs to be transmitted to the third generation
• ICPI determination: ≥0.7 is a characteristic of a strong strain

2. Hemagglutination (HA) and hemagglutination inhibition (HI) test

Upgrade of molecular diagnostic technology

RT-PCR detection

The primers designed for the F gene can amplify a 535bp fragment. The key judgment points are:

• Position 117 of the F protein must be phenylalanine
• Positions 113-116 of the F2 protein must contain ≥3 basic amino acids

Real-time fluorescence RT-PCR

New probe NDV-Ip (FAM/BHQ-1 marker) increases the detection sensitivity by 10 times:

Implementation recommendations

1. Laboratory classification: Virus isolation must be performed in a BSL-3 laboratory, and nucleic acid testing can be performed in a BSL-2 laboratory
2. Sample transportation: Tissue samples must be stored at -20°C, and swab samples must avoid repeated freezing and thawing (≤3 times)
3. Method selection: Real-time fluorescence RT-PCR is the first choice for rapid screening, and strain identification must be combined with ICPI determination