Main achievements of the World Organisation for Animal Health/United Nations Food and Agriculture Organization network on animal influenza.

The World Organisation for Animal Health (OIE)/United Nations Food and Agriculture Organization (FAO) joint network of expertise on animal influenza (OFFLU) includes all ten OIE/FAO reference laboratories and collaborating centers for avian influenza, other diagnostic laboratories, research and academic institutions, and experts in the fields of virology, epidemiology, vaccinology, and molecular biology. OFFLU has made significant progress in improving its infrastructure, in identifying and addressing technical gaps, and in establishing associations among leading veterinary institutions. Interaction with the World Health Organization (WHO) Global Influenza Program is also critical, and mechanisms for permanent interaction are being developed. OFFLU played a key role in the WHO/OIE/FAO Joint Technical Consultation held in Verona (October 7-9, 2008), which provided an opportunity to highlight and share knowledge and identify potential gaps regarding issues at the human-animal interface for avian influenza. OFFLU experts also contributed to the working group for the Unified Nomenclature System for H5N1 influenza viruses based on hemagglutinin gene phylogeny (WHO/OIE/FAO, H5N1 Evolution Working Group, Towards a unified nomenclature system for highly pathogenic avian influenza virus (H5N1) in Emerging Infectious Diseases 14:el, 2008). OFFLU technical activities, led by expert scientists from OIE/FAO reference institutions and coordinated by OIE and FAO focal points, have been prioritized to include commercial diagnostic kit evaluation, applied epidemiology, biosafety, vaccination, proficiency testing, development of standardized reference materials for sera and RNA, and issues at the human-animal interface. The progress to date and future plans for these groups will be presented. OFFLU is also involved in two national projects implemented by FAO in Indonesia and Egypt that seek to establish sustainable mechanisms for monitoring virus circulation, including viral characterization, and for streamlining the process to update poultry vaccines for avian influenza.

Evolutionary dynamics of Newcastle disease virus.

A comprehensive dataset of NDV genome sequences was evaluated using bioinformatics to characterize the evolutionary forces affecting NDV genomes. Despite evidence of recombination in most genes, only one event in the fusion gene of genotype V viruses produced evolutionarily viable progenies. The codon-associated rate of change for the six NDV proteins revealed that the highest rate of change occurred at the fusion protein. All proteins were under strong purifying (negative) selection; the fusion protein displayed the highest number of amino acids under positive selection. Regardless of the phylogenetic grouping or the level of virulence, the cleavage site motif was highly conserved implying that mutations at this site that result in changes of virulence may not be favored. The coding sequence of the fusion gene and the genomes of viruses from wild birds displayed higher yearly rates of change in virulent viruses than in viruses of low virulence, suggesting that an increase in virulence may accelerate the rate of NDV evolution.

Biological and phylogenetic characterization of pigeon paramyxovirus serotype 1 circulating in wild North American pigeons and doves.

As part of West Nile virus surveillance programs in Rhode Island and eastern Texas between 2000 and 2007, brain tissue was collected from 5,608 dead birds representing 21 avian orders found in public places or reported by homeowners. Fifteen Newcastle disease virus isolates were recovered only from birds of the order Columbiformes and were positively identified by the USDA-validated real-time reverse transcription-PCR assay targeting the matrix gene and more specifically as pigeon paramyxovirus serotype 1 (PPMV-1) by hemagglutinin inhibition with monoclonal antibodies. Based upon partial genomic sequencing and phylogenetic analysis, the newly isolated viruses represent a distinct sublineage within class II genotype VIb. All of the viruses (15/15) were classified as virulent based upon their fusion cleavage site motif ((112)RRKKRF(117)) and intracerebral pathogenicity indices of >0.7 (ranging from 0.98 to 1.35); however, these viruses escaped detection by the fusion gene-based real-time PCR test for virulence. Modifications introduced to the probe site of the fusion gene-based assay allowed rapid virulence detection within this distinct sublineage.

Isolation and genetic characterization of avian influenza viruses and a Newcastle disease virus from wild birds in Barbados: 2003-2004.

Zoonotic transmission of an H5N1 avian influenza A virus to humans in 2003-present has generated increased public health and scientific interest in the prevalence and variability of influenza A viruses in wild birds and their potential threat to human health. Migratory waterfowl and shorebirds are regarded as the primordial reservoir of all influenza A viral subtypes and have been repeatedly implicated in avian influenza outbreaks in domestic poultry and swine. All of the 16 hemagglutinin and nine neuraminidase influenza subtypes have been isolated from wild birds, but waterfowl of the order Anseriformes are the most commonly infected. Using 9-to-11-day-old embryonating chicken egg culture, virus isolation attempts were conducted on 168 cloacal swabs from various resident, imported, and migratory bird species in Barbados during the months of July to October of 2003 and 2004. Hemagglutination assay and reverse transcription-polymerase chain reaction were used to screen all allantoic fluids for the presence of hemagglutinating agents and influenza A virus. Hemagglutination positive-influenza negative samples were also tested for Newcastle disease virus (NDV), which is also found in waterfowl. Two influenza A viruses and one NDV were isolated from Anseriformes (40/168), with isolation rates of 5.0% (2/40) and 2.5% (1/40), respectively, for influenza A and NDV. Sequence analysis of the influenza A virus isolates showed them to be H4N3 viruses that clustered with other North American avian influenza viruses. This is the first report of the presence of influenza A virus and NDV in wild birds in the English-speaking Caribbean.

Phylogenetic diversity among low-virulence newcastle disease viruses from waterfowl and shorebirds and comparison of genotype distributions to those of poultry-origin isolates.

Low-virulence Newcastle disease viruses (loNDV) are frequently recovered from wild bird species, but little is known about their distribution, genetic diversity, or potential to cause disease in poultry. NDV isolates recovered from cloacal samples of apparently healthy waterfowl and shorebirds (WS) in the United States during 1986 to 2005 were examined for genomic diversity and their potential for virulence (n = 249). In addition 19 loNDV isolates from U.S. live bird markets (LBMs) were analyzed and found to be genetically distinct from NDV used in live vaccines but related to WS-origin NDV. Phylogenetic analysis of the fusion protein identified nine novel genotypes among the class I NDV, and new genomic subgroups were identified among genotypes I and II of the class II viruses. The WS-origin viruses exhibited broad genetic and antigenic diversity, and some WS genotypes displayed a closer phylogenetic relationship to LBM-origin NDV. All NDV were predicted to be lentogenic based upon sequencing of the fusion cleavage site, intracerebral pathogenicity index, or mean death time in embryo assays. The USDA real-time reverse transcription-PCR assay, which targets the matrix gene, identified nearly all of the class II NDV tested but failed to detect class I viruses from both LBM and WS. The close phylogenetic proximity of some WS and LBM loNDV suggests that viral transmission may occur among wild birds and poultry; however, these events may occur unnoticed due to the broad genetic diversity of loNDV, the lentogenic presentation in birds, and the limitations of current rapid diagnostic tools.

Characterization of class I Newcastle disease virus isolates from Hong Kong live bird markets and detection using real-time reverse transcription-PCR.

Newcastle disease viruses isolated from Hong Kong live bird markets (LBMs) were not detected by a USDA-validated matrix gene real-time reverse transcription-PCR (RT-PCR) assay. Based upon phylogenetic analysis of the fusion gene, these viruses were related to lentogenic class I viruses found in U.S. LBMs and wild waterfowl. An alternative real-time RT-PCR assay which complements the matrix gene assay was developed to efficiently detect class I viruses.

Effect of probe-site mismatches on detection of virulent Newcastle disease viruses using a fusion-gene real-time reverse transcription polymerase chain reaction test.

Virulent forms of Newcastle disease virus (NDV) are a major concern for poultry producers around the world and the rapid diagnosis of an outbreak is crucial to any control program. A validated real-time reverse transcription-PCR test (fusion test) directed at the fusion-cleavage site of NDV was developed to differentiate virulent Newcastle disease virus strains from those of low virulence, however one virulent isolate, Dove/Italy/2736/2000, escaped detection during the initial evaluation of the test. The objectives of this study were to determine how this isolate differed from other detectable isolates, to identify other isolates that may fail detection, and to characterize the effect of specific probe-site mutations on the fusion test at a range of annealing temperatures. Using a virulent NDV isolate (Game fowl/US(CA)/2002) as a backbone that has 100% identity to the fusion-test probe, specific changes were made to the fusion-test probe-site to reflect the unique mismatches found in Dove/Italy/2736/2000 and other selected regions of the probe. Mutated clones with mismatches unique to Dove/Italy/2736/2000 at positions 6, 13, and 14 were not detected until annealing temperatures were lowered to 50 degrees C. Those detected at 58 degrees C contained 1-2 mismatches (position 1 and 6, 13 and 14, or 14 only) although increased cycle threshold values compared to the parent clone indicated decreased sensitivity. Data from this study predicts that the fusion test may fail to detect some viruses among lineage 4b and potential solutions to identify this subset of viruses include lowering the annealing temperature or modifying the probe.