Several new highly pathogenic (HP) H5 avian influenza virus (AIV) have been detected in poultry farms from south-western France since November 2015, among which an HP H5N1. The zoonotic potential and origin of these AIVs immediately became matters of concern. One virus of each subtype H5N1 (150169a), H5N2 (150233) and H5N9 (150236) was characterised. All proved highly pathogenic for poultry as demonstrated molecularly by the presence of a polybasic cleavage site in their HA protein – with a sequence (HQRRKR/GLF) previously unknown among avian H5 HPAI viruses – or experimentally by the in vivo demonstration of an intravenous pathogenicity index of 2.9 for the H5N1 HP isolate. Phylogenetic analyses based on the full genomes obtained by NGS confirmed that the eight viral segments of the three isolates were all part of avian Eurasian phylogenetic lineage but differed from the Gs/Gd/1/96-like lineage. The study of the genetic characteristics at specific amino acid positions relevant for modulating the adaptation to and the virulence for mammals showed that presently, these viruses possess most molecular features characteristic of AIV and lack some major characteristics required for efficient respiratory transmission to or between humans. The three isolates are therefore predicted to have no significant pandemic potential.

In southwestern France, during the winter of 2016–2017, the rapid spread of highly pathogenic avian influenza H5N8 outbreaks despite the implementation of routine control measures, raised the question about the potential role of airborne transmission in viral spread. As a first step to investigate the plausibility of that transmission, air samples were collected inside, outside and downwind from infected duck and chicken facilities. H5 avian influenza virus RNA was detected in all samples collected inside poultry houses, at external exhaust fans and at 5 m distance from poultry houses. For three of the five flocks studied, in the sample collected at 50–110 m distance, viral genomic RNA was detected. The measured viral air concentrations ranged between 4.3 and 6.4 log10 RNA copies per m3, and their geometric mean decreased from external exhaust fans to the downwind measurement point. These findings are in accordance with the possibility of airborne transmission and question the procedures for outbreak depopulation.

No abstract

I nfluenza A viruses are enveloped viruses of the Alphainfluenzavirus genus in the Orthomyxoviridae family. Their negative-stranded RNA genome consists of 8 segments encoding a total of 10-14 proteins. Avian influenza viruses (AIVs) are classified on the basis of antigenic differences in their surface glycoproteins, hemagglutinin (H1-H16) and neuraminidase (N1-N9) (1). H5 and H7 subtypes can become highly pathogenic avian influenza (HPAI) viruses after the evolution of multiple basic amino acids in the cleavage site of hemagglutinin protein (2,3). This mutation enables the virus to replicate efficiently in all organs, causing a severe and often fatal systemic disease. In contrast, the cleavage site of hemagglutinin in low pathogenicity AIVs lacks these multiple amino acids, restricting viral replication to the respiratory and digestive tracts. Low pathogenicity AIVs cause subclinical or mild disease that can be aggravated by secondary infections (4,5). Because H5 and H7 AIVs can evolve to be highly pathogenic, the diseases caused by these subtypes are notifiable to national and international bodies (6). Since 1996, highly pathogenic H5 viruses of the A/goose/Guangdong/1/96 (Gs/GD/96) lineage have caused recurrent outbreaks with high death rates in birds. These HPAIs are categorized into 10 distinct clades (0-9) on the basis of hemagglutinin sequences (7). These clades are found in Asia; a few have spread to Africa, Europe, and North America (8-10). Europe experienced major introductions of H5N1 of clade 2.2 during 2005-2007 and H5N8 of clade 2.3.4.4 during 2014-2020 (11-14). Many reassortments were observed on Gs/Gd/1/96-like viruses, especially within clade 2.3.4.4. The reassortments generated several subtypes including H5N1, H5N2, H5N5, H5N6, and H5N8 (11,15-17). During winter 2016-17, twenty-nine countries in Europe reported 1,576 cases of Gs/Gd/1/96like H5N8 infections in wild birds and 1,134 in poultry, especially domestic ducks (18). During this outbreak, researchers identified 6 HPAI A(H5N8) genotypes in Europe; 2 of these genotypes were identified using 6 sequences from infected birds in France (19). France had 539 cases of HPAI A(H5N8) infections, 51 in wild birds and 488 in poultry flocks, most of which occurred at duck farms producing foie gras (18). A previous study used spatiotemporal analysis of clinical cases comprising 2 distinct epizootic periods in southwestern France (20). The first period spanned November 28, 2016-February 2, 2017 and comprised 4 spatiotemporal clusters (20). The second period spanned February 3-March 23, 2017 and comprised a single spatiotemporal cluster (20).

In late 2000, Italy was the first country of the European Union (EU) to implement an emergency vaccination programme against notifiable avian influenza. Vaccination with a conventional vaccine containing a seed strain with a different neuraminidase subtype from that of the field virus was used to complement biosecurity and restriction measures as part of an overall eradication strategy. This vaccination technique, in line with the Differentiating Infected from Vaccinated Animals system (DIVA), was applied several times until March 2008. This strategy enabled the identification of field exposed flocks and ultimately the eradication of low pathogenic H7N1, H7N3 and H5N2 infections. Italy was also the first country to implement a bivalent H5/H7 prophylactic vaccination programme of defined poultry populations, which was discontinued in December 2006. Following the incursion of highly pathogenic H5N1 into Europe, in 2005 and 2006, two other EU Member States, namely France and the Netherlands, implemented preventive vaccination programmes in 2006 but they targeted selected poultry populations different from those targeted in Italy and were implemented for short periods of time. Data generated during six years of experience with vaccination against avian influenza in Italy indicate that it is a useful tool to limit secondary spread and possibly prevent the introduction of low pathogenic avian influenza viruses in a susceptible population. The experience of France and the Netherlands provides data on vaccination of ducks and hobby poultry respectively and monitoring programmes associated with vaccination and difficulties related to their application. The advantages and disadvantages of vaccination need to be considered in the decision-making process, including the financial aspects of vaccination.

No abstract

Prevalence of avian influenza infection in free-range mule ducks (a cross between Muscovy [Cairina moschata domesticus] and Pekin ducks [Anas platyrhychos domesticus]) is a matter of concern and deserves particular attention. Thus, cloacal swabs were collected blindly from 30 targeted mule flocks at 4, 8, and 12 wk of age between October 2004 and January 2005. They were stored until selection. On the basis of a positive H5 antibody detection at 12 wk of age with the use of four H5 antigens, the samples from eight flocks were selectively analyzed. Positive samples were first screened with a matrix gene-based real-time reverse transcriptase-polymerase chain reaction assay before virus isolation. Eight avian influenza subtypes (H5N1, H5N2, H5N3, H6N2, H6N8, and H11N9) and three avian paramyxovirus type 1 viruses were isolated. All 11 are characterized as low pathogenicity (LP) and avirulent, respectively, by in vivo tests and, when relevant, nucleotide sequencing of the hemagglutinin (or fusion [F]) protein cleavage site. Regarding H5 isolates, all of their eight genes belong to the avian lineage and some particular genetic traits were determined. H5 genes were fully sequenced and phylogenetically analyzed; they all belong to the Eurasian lineage, lack additional glycosylation sites, and do not cluster, suggesting separate introductions from the wild reservoir. None were grouped with the Asian isolates. The N1 gene (H5N1 isolate) was very close genetically to an Italian LP-H7N1 gene. Antigenic relationships between these H5 isolates and others were assessed comparatively by crossed hemagglutination inhibition tests. All these data are very useful to control the evolution of H5 viruses at the genetic and antigenic level to better understand the source of new outbreaks (new introductions from wild birds or the result of spread among poultry) and to assess the immunity afforded by available vaccines. These data are useful also to update antigens for avian influenza survey and to choose the most suitable vaccine in the case of preventive vaccination of ducks.

In autumn/winter 2016–2017, HPAI-H5N8 viruses belonging to the A/goose/Guandong/1/1996 (Gs/Gd) lineage, clade 2.3.4.4b, were responsible for outbreaks in domestic poultry in Europe, and veterinarians were requested to reinforce surveillance of pigs bred in HPAI-H5Nx confirmed mixed herds. In this context, ten pig herds were visited in southwestern France from December 2016 to May 2017 and serological analyses for influenza A virus (IAV) infections were carried out by ELISA and hemagglutination inhibition assays. In one herd, one backyard pig was shown to have produced antibodies directed against a virus bearing a H5 from clade 2.3.4.4b, suggesting it would have been infected naturally after close contact with HPAI-H5N8 contaminated domestic ducks. Whereas pigs and other mammals, including humans, may have limited sensitivity to HPAI-H5 clade 2.3.4.4b, this information recalls the importance of implementing appropriate biosecurity measures in pig and poultry farms to avoid IAV interspecies transmission, a prerequisite for co-infections and subsequent emergence of new viral genotypes whose impact on both animal and human health cannot be predicted.