Multiple independent introductions of highly pathogenic avian influenza H5 viruses during the 2020-2021 epizootic in France.

During winter 2020-2021, France and other European countries were severely affected by highly pathogenic avian influenza H5 viruses of the Gs/GD/96 lineage, clade 2.3.4.4b. In total, 519 cases occurred, mainly in domestic waterfowl farms in Southwestern France. Analysis of viral genomic sequences indicated that 3 subtypes of HPAI H5 viruses were detected (H5N1, H5N3, H5N8), but most French viruses belonged to the H5N8 subtype genotype A, as Europe. Phylogenetic analyses of HPAI H5N8 viruses revealed that the French sequences were distributed in 9 genogroups, suggesting 9 independent introductions of H5N8 from wild birds, in addition to the 2 introductions of H5N1 and H5N3.

Highly Pathogenic Avian Influenza A(H5N8) Virus Spread by Short- and Long-Range Transmission, France, 2016-17.

We detected 3 genotypes of highly pathogenic avian influenza A(H5N8) virus in France during winter 2016-17. Genotype A viruses caused dramatic economic losses in the domestic duck farm industry in southwestern France. Our phylogenetic analysis suggests that genotype A viruses formed 5 distinct geographic clusters in southwestern France. In some clusters, local secondary transmission might have been started by a single introduction. The intensity of the viral spread seems to correspond to the density of duck holdings in each production area. To avoid the introduction of disease into an unaffected area, it is crucial that authorities limit the movements of potentially infected birds.

An enzyme-linked immunosorbent assay for detection of avian influenza virus subtypes H5 and H7 antibodies.

BACKGROUND: Avian influenza virus (AIV) subtypes H5 and H7 attracts particular attention because of the risk of their potential pathogenicity in poultry. The haemagglutination inhibition (HI) test is widely used as subtype specific test for serological diagnostics despite the laborious nature of this method. However, enzyme-linked immunosorbent assays (ELISAs) are being explored as an alternative test method.H5 and H7 specific monoclonal antibodies were experimentally raised and used in the development of inhibition ELISAs for detection of serological response specifically directed against AIV subtypes H5 and H7. The ELISAs were evaluated with polyclonal chicken anti-AIV antibodies against AIV subtypes: H1N2, H5N2, H5N7, H7N1, H7N7, H9N9, H10N4 and H16N3. RESULTS: Both the H5 and H7 ELISA proved to have a high sensitivity and specificity and the ELISAs detected H5 and H7 antibodies earlier during experimental infection than the HI test did. The reproducibility of the ELISA's performed at different times was high with Pearson correlation coefficients of 0.96-0.98. CONCLUSIONS: The ELISAs are a potential alternative to the HI test for screening of large amounts of avian sera, although only experimental sera were tested in this study.

Different domains of the RNA polymerase of infectious bursal disease virus contribute to virulence.

BACKGROUND: Infectious bursal disease virus (IBDV) is a pathogen of worldwide significance to the poultry industry. IBDV has a bi-segmented double-stranded RNA genome. Segments A and B encode the capsid, ribonucleoprotein and non-structural proteins, or the virus polymerase (RdRp), respectively. Since the late eighties, very virulent (vv) IBDV strains have emerged in Europe inducing up to 60% mortality. Although some progress has been made in understanding the molecular biology of IBDV, the molecular basis for the pathogenicity of vvIBDV is still not fully understood. METHODOLOGY, PRINCIPAL FINDINGS: Strain 88180 belongs to a lineage of pathogenic IBDV phylogenetically related to vvIBDV. By reverse genetics, we rescued a molecular clone (mc88180), as pathogenic as its parent strain. To study the molecular basis for 88180 pathogenicity, we constructed and characterized in vivo reassortant or mosaic recombinant viruses derived from the 88180 and the attenuated Cu-1 IBDV strains. The reassortant virus rescued from segments A of 88180 (A88) and B of Cu-1 (BCU1) was milder than mc88180 showing that segment B is involved in 88180 pathogenicity. Next, the exchange of different regions of BCU1 with their counterparts in B88 in association with A88 did not fully restore a virulence equivalent to mc88180. This demonstrated that several regions if not the whole B88 are essential for the in vivo pathogenicity of 88180. CONCLUSION, SIGNIFICANCE: The present results show that different domains of the RdRp, are essential for the in vivo pathogenicity of IBDV, independently of the replication efficiency of the mosaic viruses.

The epidemiology of the highly pathogenic H5N1 avian influenza in Mute Swan (Cygnus olor) and other Anatidae in the Dombes region (France), 2006.

In February 2006, a highly pathogenic avian influenza (HPAI) H5N1 virus was isolated from Common Pochards (Aythia ferina) in the Dombes region of France, an important migrating and wintering waterfowl area. Thereafter, HPAI H5N1 virus was isolated from 39 swab pools collected from dead waterfowl found in the Dombes, but only from three pooled samples collected outside of this area but located on the same migration flyway. A single turkey farm was infected in the Dombes. The epizootic lasted 2 mo and was restricted to the Dombes area. Virus-positive pools were detected in 20 of 1,200 ponds and infected Mute Swans (Cygnus olor) represented 82% of the virus-positive pools. Other infected species included Common Pochard (n=4), Grey Heron (Ardea cinerea, n=1), Eurasian Buzzard (Buteo buteo, n=1), and Greylag Goose (Anser anser, n=1). Despite intensive monitoring during and after the outbreak, HPAI H5N1 virus was not isolated from healthy wild birds. Our results are consistent with an HPAI H5N1-virus introduction into the Dombes via migrating ducks. These birds could have been pushed west by a severe cold spell in central Europe where the virus had already been detected. The Mute Swan served as an excellent epidemiologic sentinel during this outbreak; swans appear to be highly sensitive to infection with these viruses and swan mortality was easy to detect. During the outbreak, the mortality rates for wild birds remained moderate and the virus affected a limited number of species.

Assessment of the protection afforded by triple baculovirus recombinant coexpressing H5, N3, M1 proteins against a homologous H5N3 low-pathogenicity avian influenza virus challenge in Muscovy ducks.

In Asia, domestic ducks have been shown to play a pivotal role in H5 high-pathogenicity avian influenza virus transmission. We have also observed that the same situation may exist for H5 low-pathogenicity avian influenza (LPAI) virus. No data are available regarding the protection afforded by commercial inactivated vaccines against H5 LPAI virus infection in ducks, and two preliminary experiments using commercial inactivated vaccines gave poor results. Virus-like particles (VLPs) have been shown to be immunogenic in different species. With regard to the influenza model, the matrix (M) protein has been shown to be necessary for the formation of VLPs. In order to attempt to develop a VLP influenza vaccine expressing hemagglutinin and neuraminidase (NA) of interest, we generated a triple recombinant baculovirus (rB) expressing three structural proteins: H5, N3, and M, derived from a recent French LPAI virus strain. Although the three proteins were successfully expressed in rB-infected cells and displayed the expected biological activity, no VLPs were observed. Despite this result, the protection afforded to ducks by rB-infected cell lysates was assessed and was compared with the protection afforded by an inactivated commercial H5N9 vaccine. For this purpose, specific-pathogen-free Muscovy ducks (15 per group) received rB-infected cell lysates (3 wk apart), while a second group received the H5N9 vaccine. Ten days after the boost, a homologous virus challenge was implemented. Both vaccines induced positive hemagglutination inhibition titers and M immune response, whereas lysates of rB-infected cells elicited NA immune response. Tracheal and cloacal sheddings were measured using M-based real-time-reverse transcription-polymerase chain reaction and were compared with the sheddings of vaccinated and unvaccinated infected controls. Lysates of rB-infected cells afforded a significant decrease of cloacal shedding and a delayed peak of tracheal shedding, whereas the inactivated commercial vaccine afforded a significant decrease of tracheal shedding only.

Baculovirus-expressed muscovy duck reovirus sigmaC protein induces serum neutralizing antibodies and protection against challenge.

Recombinant baculoviruses with sigmaC- or sigmaB-encoding gene from muscovy duck reovirus (DRV) were constructed. Western-blot analysis showed that sigmaC was more immunoreactive than sigmaB. Vaccination of SPF ducks with two injections, 3 weeks apart, of emulsions containing sigmaC or sigmaC + sigmaB elicited DRV-specific neutralizing antibodies. Following challenge, vaccination partially--or even totally in some cases--prevented the appearance of clinical symptoms. Moreover, immunization reduced the severity of reovirus-induced tenosynovitis and prevented pericarditis development during the course of the assay. Thus, DRV sigmaC, alone or co-expressed with sigmaB, appeared as a good candidate for vaccination of ducks (96/100 mots).