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For many years, it has been known that the IAV gene pool circulates in avian reservoir populations as low-pathogenic avian influenza viruses (LPAIVs), which, with respect to the H5 and H7 antigenic subtypes, can occasionally mutate in poultry into highly pathogenic (HP) AIVs, which are feared for their potential impact on animal and public health [[6]]. Hemagglutination-inhibition (HI)-positive test results - likely indicating infection with Gs/GD/96-lineage H5Nx HPAI viruses - were obtained every year with annual proportions ranging from 7.1% to 77.2%, thus suggesting the persistent, but intermittent, circulation of Gs/GD/96-lineage H5Nx HPAI viruses in domestic ducks and possible bi-directional spillover between domestic and wild birds. 25564096 20 Pérez-Ramírez E., Acevedo P., Allepuz A., Gerrikagoitia X., Alba A., Busquets N., Díaz-Sánchez S., Álvarez V., Abad F.X., Barral M. Ecological factors driving avian influenza virus dynamics in Spanish wetland ecosystems. Wild aquatic birds constitute the main natural reservoir of the influenza A virus (IAV) gene pool, from which novel IAVs can emerge to infect other animals including avian and mammalian species. [Extracted from the article]

Background: Avian influenza viruses (AIVs) are endemic in wild birds and their introduction and conversion to highly pathogenic avian influenza virus in domestic poultry is a cause of serious economic losses as well as a risk for potential transmission to humans. The ability to rapidly recognise AIVs in biological specimens is critical for limiting further spread of the disease in poultry. The advent of molecular methods such as real time polymerase chain reaction has allowed improvement of detection methods currently used in laboratories, although not all of these methods include an Internal Positive Control (IPC) to monitor for false negative results. Therefore we developed a one-step reverse transcription real time PCR (RRT-PCR) with a Minor Groove Binder (MGB) probe for the detection of different subtypes of AIVs. This technique also includes an IPC. Methods: RRT-PCR was developed using an improved TaqMan technology with a MGB probe to detect AI from reference viruses. Primers and probe were designed based on the matrix gene sequences from most animal and human A influenza virus subtypes. The specificity of RRT-PCR was assessed by detecting influenza A virus isolates belonging to subtypes from H1-H13 isolated in avian, human, swine and equine hosts. The analytical sensitivity of the RRT-PCR assay was determined using serial dilutions of in vitro transcribed matrix gene RNA. The use of a rodent RNA as an IPC in order not to reduce the efficiency of the assay was adopted. Results: The RRT-PCR assay is capable to detect all tested influenza A viruses. The detection limit of the assay was shown to be between 5 and 50 RNA copies per reaction and the standard curve demonstrated a linear range from 5 to 5 × 108 copies as well as excellent reproducibility. The analytical sensitivity of the assay is 10-100 times higher than conventional RT-PCR. Conclusion: The high sensitivity, rapidity, reproducibility and specificity of the AIV RRT-PCR with the use of IPC to monitor for false negative results can make this method suitable for diagnosis and for the evaluation of viral load in field specimens. [ABSTRACT FROM AUTHOR]

A response by Simona Puzelli, Livia Di Trani, Concetta Fabiani, and Laura Campitelli to a letter to the editor about their article "Serological Analysis of Serum Samples From Humans Exposed to Avian H7 Influenza Viruses in Italy Between 1999 and 2003," in the 2005 issue.

Since the “bird flu” incident in Hong Kong SAR in 1997, several studies have highlighted the substantial role of domestic birds, such as turkeys and chickens, in the ecology of influenza A viruses. Even if recent evidence suggests that chickens can maintain several influenza serotypes, avian influenza viruses (AIVs) circulating in domestic species are believed to be introduced each time from the wild bird reservoir. However, so far the direct precursor of influenza viruses from domestic birds has never been identified. In this report, we describe the antigenic and genetic characterization of the surface proteins of H7N3 viruses isolated from wild ducks in Italy in 2001 in comparison to H7N3 strains that circulated in Italian turkeys in 2002–2003. The wild and domestic avian strains appeared strictly related at both phenotypic and genetic level: homology percentages in seven of their genes were comprised between 99.8% (for PB2) and 99.1% (for M), and their NA genes differed mainly because of a 23-aminoacid deletion in the NA stalk. Outside this region of the molecule, the NAs of the two virus groups showed 99% similarity. These findings indicate that turkey H7N3 viruses were derived “in toto” from avian influenza strains circulating in wild waterfowl 1 year earlier, and represent an important step towards the comprehension of the mechanisms leading to interspecies transmission and emergence of potentially pandemic influenza viruses. [Copyright &y& Elsevier]