Title: Characterization of the 2012 highly pathogenic H7N3 virus in Mexico: pathobiology and vaccine protection Authors
|Ricardez, Yadira -|
|Guzman, Sofia -|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 18, 2014
Publication Date: N/A
Technical Abstract: In June of 2012, a H7N3 highly pathogenic avian influenza (HPAI) virus was identified as the cause of a severe disease outbreak in commercial laying chicken farms in Mexico. Since that time the virus has spread to many surrounding States and new outbreaks continue to be reported. The Jalisco virus had high sequence similarity of greater than 97% to wild bird viruses from North America in all eight gene segments. The hemagglutinin gene of the virus contained a 24 nucleotide insert at the hemagglutinin cleavage site which had a 100% sequence identity to chicken 28s ribosomal RNA, suggesting the insert was non-homologous recombination with the host genome. In pathogenesis studies, intranasally inoculated adult and young chickens became infected and died between 2 and 4 days post inoculation (dpi). Some of the chickens lacked clinical signs (peracute disease), while some showed nonspecific clinical signs such as ruffled feathers, lethargy, anorexia and prostration, and other chickens had severe respiratory distress, facial edema, cyanotic combs, wattles and legs. For vaccine protection studies, both U.S. H7 low pathogenic (LP) AI viruses and a 2006 Mexican H7 LPAI virus were tested as antigen in experimental oil emulsion vaccines and injected into chickens three weeks prior to challenge. All H7 vaccines tested provided >90 % protection against clinical disease after challenge and decreased the number of birds shedding and the titers of viral shedding. In a second experiment, 26 week-old egg-laying hens were vaccinated either singly or doubly and challenged against the HPAI virus. All vaccinated birds reduced shedding of virus compared to sham vaccinated birds, however swabs of eggs recovered from vaccinated hens were positive for virus. These studies demonstrate the pathological consequence of the 2012 Mexican lineage H7N3 HPAI infection of chickens and provide support for vaccination of poultry as part of an eradication program against this virus.