Genetic variability of avian influenza virus subtype H5N8 in Egypt in 2017 and 2018

Pathogenicity of three genetically distinct and highly pathogenic Egyptian H5N8 avian influenza viruses in chickens

“…In late 2016 and early 2017, three distinguishable genotypes of H5N8 viruses have been reported [21], the rst was represented by strain A/common-coot/Egypt/CA285/2016 (CA285) that was isolated from wild birds, the second was represented by A/duck/Egypt/SS19/2017 (SS19) that was isolated from backyard ducks and the third was represented by A/duck/Egypt/F446/2017 (F446) isolated from commercial duck farms. The F446 genotype became the predominant H5N8 circulating in Egypt containing PA and NP segments similar to A/mallard/Republic of Georgia/13/2011 (H6N2), while the remaining segments were more closely related to A/H5N8 viruses in wild birds from Uvs-Nuur Lake in south Russia (2016) [19]. The same reassortment pattern has been identi ed in Germany in many cases in wild birds in November 2016 [23].…”

“…It indicates the higher transmissibility of F446 to the sentinel contact birds and higher spread from contact to other birds. The outperformance of the F446 strain compared to the other tested H5N8 strains in chickens may explain previous ndings showing that F446-like reassortant strain is the predominant H5N8 strain in Egypt [19,36,37,38]. And by the presence of multiple strains of avian in uenza H5N1, H5N8 and H9N2 [37,38] has predict many future recombinations as recorded in the novel reassortant H5N2 that showed 98-99% similarity with F446 suggesting that F446 is the donor virus and N2 from Egyptian H9N2 [24].…”

“…Since May/June 2016, HPAI-H5N8 clade 2.3.4.4b has caused panzootic waves across Asia, Europe, the Middle East, and Africa [31,32]. In Egypt, the virus was rst detected in wild birds in northern Egypt in late 2016 [17], since then it has spread all over Egypt and has been isolated from several different poultry production sectors causing massive economic losses [19]. A few months after the introduction of the virus to Egypt, a genotyping study revealed a multiple incursion pattern of HPAI-H5N8 viruses into Egypt [21] The rst genotypes were recovered from wild birds in November 2016 (CAO285), followed by backyard ducks in January 2017 (SS19) and commercial duck farms in April 2017 (F446).…”

“…All three of these genotypes showed high nucleotide similarity at the level of HA, NA, M, and NS gene segments close to 2.3.4.4b Russia-Mongolia 2016 reassortant isolates (eg., A/great crested grebe/Uvs-Nuur Lake/341/2016 (H5N8)), with PB2, PB1, PA and/or NP segments originated from different in uenza viruses circulated in Asia and Europe [21]. Here, we investigated the difference in the pathogenicity and transmissibility of these three viruses in chickens that may help explain the current predominance of the F446-like strains [19] and its higher potential for reassortment [24]. To this end, IVPI, lethality, virus shedding, and dissemination in different organs, transmissibility as well as micro-pathogenicity were investigated in chickens infected with viruses representing these different genotypes.…”

“…In Egypt, H5N8 HPAI Clade 2.3.4.4 group B was rst reported late 2016 in wild birds on the north coast [17,18]. From late 2016 to the present day, H5N8 has spread all over Egypt [19] and became the predominant HPAI-H5 virus in circulation, replacing the H5N1 viruses without any reported human cases [20]. Genetic analysis has revealed multiple introductions of reassortant H5N8 viruses [21,22].…”