Distribution of avian influenza H5N1 viral RNA in tissues of AI-vaccinated and unvaccinated contact chickens after experimental infection

Abstract

Avian influenza due to highly pathogenic avian influenza (HPAIV) H5N1 virus is not a food-borne illness but a serious panzootic disease with the potential to be pandemic. In this study, broiler chickens were vaccinated with commercial H5N1 or H5N2 inactivated vaccines prior to being challenged with an HPAIV H5N1 (clade 2.2.1 classic) virus. Challenged and non-challenged vaccinated chickens were kept together, and unvaccinated chickens served as contact groups. Post-challenge samples from skin and edible internal organs were collected from dead and sacrificed (after a 14-day observation period) birds and tested using qRT-PCR for virus detection and quantification. H5N1 vaccine protected chickens against morbidity, mortality and transmission. Virus RNA was not detected in the meat or edible organs of chickens vaccinated with H5N1 vaccine. Conversely, H5N2 vaccine did not confer clinical protection, and a significant virus load was detected in the meat and internal organs. Phylogenetic analysis showed that the H5N1 virus vaccine and challenge virus strains are closely related. The results of the present study strongly suggest a need for proper selection of vaccines and their routine evaluation against newly emergent field viruses. These actions will help to reduce human exposure to HPAIV H5N1 virus from both infected live birds and slaughtered poultry. In addition, rigorous preventive measures should be put in place in order to minimize the public-health risks of avian influenza at the human-animal interface.

Predicting Hotspots for Influenza Virus Reassortment

“…Control measures could include compensation plans and vaccination of poultry with a recently developed subtype H5N1 vaccine that is more effective than previous vaccines against strains circulating in Egypt ( 10 ). Reporting of poultry disease outbreaks in Lower Egypt is poor ( 31 ), probably because farmers fear loss of income if authorities cull their flocks.…”

“…The dataset for subtype H5N1 infections during 2009–2012 consisted of 453 cases among poultry in backyard flocks, farms, and live-bird markets in 35 markazes. Screening assays are described elsewhere ( 10 ). See Technical Appendix Figure 1, for a workflow analysis.…”

Isolation of avian influenza H5N1 virus from vaccinated commercial layer flock in Egypt

“…In this study, anti-H5 antibody titer was low with variable individual titers (3.2 ± 4.3 log 2 ) after three successive vaccinations of Hisex brown-layers. Recent experimental studies showed that specific-pathogen-free (SPF) chickens vaccinated with this inactivated H5N1 vaccine evoked high HI titer (7.0 ± 0.8 log 2 ) and were protected against challenge with an Egyptian H5N1 virus belonged to the 2.2.1/C group [31]. Therefore, we assume that improper administration, mishandling and inappropriate storage of the vaccine [7] or suppression of the immune system (i.e.…”

Putative human and avian risk factors for avian influenza virus infections in backyard poultry in Egypt

“…Serological responses to H5-specific antibodies were detected via hemagglutination inhibition (HI) assays using four hemagglutinin units following World Organisation for Animal Health protocols (OIE, 2012). We used a 1% suspension of chicken erythrocytes in V-bottom, 96-wellmicrotiter plates (Hassan et al, 2012). Serum samples were considered positive for H5N1 at a HI titer of ≥ 1:80 (Wang et al, 2012).…”