Tests for Identifying New Strains of Newcastle Disease Virus

Research carried out by Dr Claudio L. Afonso at the USDA ARS Southeast Poultry Research Laboratory in Athens, Georgia on diagnostic tests, new assays and the release of viral genomic sequences is helping to tackle exotic Newcastle Disease, according to this US Poultry & Egg Association report.

19 February 2010

4 minute read

Exotic Newcastle disease (END) is a significant viral disease of poultry, with virulent strains responsible for major panzootics and extensive poultry mortality worldwide. The estimated direct and indirect losses from depopulation and trade restrictions in the 2002-2003 outbreak of END in the United States were greater than $262 million. If END virus (ENDV) became established in bird species with access to commercial poultry in the US, it could cost the poultry industry millions of dollars a year in increased surveillance, vaccination and eradication programmes.

Comprehensive and rapid diagnostic tests to detect and differentiate virulent strains of NDV (vNDV) from the low virulence NDV (loNDV) strains, like the widely used live Newcastle disease (ND) vaccines, are crucial for the control of END. Evaluation of ENDV sequences in the GenBank databases identified at least 289 accessions from virulent viruses from China, Taiwan, Korea, Iran, Turkey, Kazakhstan, and European countries that may fail rapid PCR-based diagnostic tests. In addition, pigeon paramyxovirus type-1 recovered from mortality events in Texas and Rhode Island during 2000-2007, and recent US cormorant NDV have genomic differences that suggests that US endemic viruses that are now reportable to World Organisation for Animal Health (OIE) may fail the test for virulence characterisation based on PCR. Evaluation of current US tests and development of new assays is needed to achieve a rapid response to an accidental or deliberate introduction of new viruses.

Results

A number of objectives to evaluate US diagnostic tests have been completed or exceeded.

A total of 159 NDV from 17 countries – US, Canada, Vietnam, Russia, Pakistan, Indonesia, Korea, Belize, Mexico, Venezuela, South Africa, Peru, Honduras, Australia, Japan, Nigeria, Kenya – were evaluated using three different US rapid detection assays. Over 577 real time PCR tests were done and the performance of these tests for each one of the 159 isolates was tabulated and partially published.

The fusion protein cleavage site of 132 new viruses and the matrix gene of four other viruses – that either failed the test or were likely to fail – was obtained and submitted to Genbank.

Three new real time PCR assays were created at SEPRL and tested against US pigeon, US cormorant and Pakistani viruses that failed detection.

Finally, five new publications have been produced.

Impact

The economic impact of preventing an outbreak is difficult to measure. The 2002 outbreak of exotic NDV in California, Nevada and Arizona caused the depopulation of 3.3 million birds. The presence of ENDV in the poultry population will cause immediate trade restriction on US poultry products.

Due to the presence of highly virulent NDV in South and Central America, the North-South migratory flyways of wild birds, and the expanding commercial trade with Asian countries the introduction of exotic NDV is not unlikely. The availability of sequence information and three new rapid tests developed by Southeast Poultry Research Laboratory will facilitate a prompt response.

Conclusions

The evaluation by the Southeast Poultry Research Laboratory of US rapid diagnostic tests, development of new assays, and release of viral genomic sequences to the public is already impacting our understanding of mobility and evolution of NDV and is leading to the development of more effective diagnostic and vaccines.