Abstract
Saudi Arabia (SA) experienced a highly pathogenic avian influenza (HPAI) H5N1 outbreak in domesticated birds in 2007. Forty-three hemagglutinin (HA) and 41 neuraminidase (NA) genes of HPAI H5N1 viruses were sequenced and phylogenetic analyses of completely sequenced genes were performed to compare with other viral HA and NA gene sequences available in the public databases. Molecular characterization of the H5N1 viruses revealed two genetically distinct clades, 2.2.2 and 2.3.1, of H5N1 viruses circulating in the area. Amino acid sequence analysis of the HA gene indicated that the virus from 2.2.2 contained the sequence SPQGERRRK-R/G at the cleavage site, while the virus from 2.3.1 contained the sequence SPQRERRRK-R/G. Additionally, a few mutations with amino acid substitutions such as M226I at N-link glycosylation site were identified in two of these isolates. Amino acid sequence of the NA gene showed a 20-amino-acid deletion in the NA stalk region, required for enhanced virulence of influenza viruses and its adaptation from wild birds to domestic chickens. As close contact between humans and birds is unavoidable, there is a need for a thorough understanding of the virus epidemiology, factors affecting the spread of the virus, and molecular characterization such as phylogeny and substitution rates of H5N1 viruses circulating in the region. Two genetically distinct clades were found to be circulating in the country, which could likely result in recombination and emergence of more virulent viral strains. These findings could be helpful for the authorities devising control measures against these viruses.
Highlights
Avian influenza is an acute infectious disease of poultry, waterfowl, wild birds, and animals, and is able to be zoonotically transmitted to humans
The Kingdom of Saudi Arabia experienced a severe outbreak of H5N1 influenza viruses in 2007
Our analysis showed that these viruses might have been introduced into the Kingdom of Saudi Arabia (KSA) by migratory birds from Mongolia and Nigeria in early 2007 (Figure 1A)
Summary
Avian influenza is an acute infectious disease of poultry, waterfowl, wild birds, and animals, and is able to be zoonotically transmitted to humans. These viruses were genetically characterized as clade 2.2 [8] Later on, these H5N1 clade 2.2 viruses were detected in wild birds and domestic poultry in various countries of Asia, Europe, and Africa. Since late 2005, both wild birds and poultry were affected by HPAI viruses subtype H5N1 in Europe, the Middle East, and Africa [11,12]. In the KSA, H5N1 infection was reported in falcons for the first time, and subsequently, the virus was isolated from imported Houbara bustards (Chlamydotis undulate macqueenii) [16] These birds are traded to the Middle East from Central Asia [17]. Understanding of virus diversity and epidemiology is essential for devising resistance and control strategies against these viruses
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