Phylogenetic Analysis of Influenza A Viruses (H6N8, H1N8, H4N2, H9N2, H10N7) Isolated from Wild Birds, Ducks, and Ostriches in South Africa from 2007 to 2009

Abstract

Influenza A strains emerging from wild birds are a constant threat to South Africa's valuable ostrich industry. In 2004 and again in 2006, low pathogenicity avian influenza H5N2 strains introduced from a wild bird reservoir mutated in ostriches to high pathogenicity avian influenza (HPAI), with serious economic consequences and export bans imposed by the European Union. Although no outbreaks of notifiable avian influenza have occurred in South Africa since 2006, the H9N2 virus caused a localized outbreak where ostriches displayed symptoms of green urine, depression, and mild morbidity. Most recently, an outbreak of H10N7 in farmed Pekin ducks (Anas platyrhynchos domestica) caused increased mortalities, but this was exacerbated by a secondary Escherichia coli infection, because an intravenous pathogenicity index of 0.00 was recorded. Each of the eight gene segments of the five strains isolated from 2007 to 2009 from farmed ostriches in the Oudtshoorn region (H6N8, H9N2), Pekin ducks (H10N7, Joostenburgvlakte region), and wild Egyptian geese (Alopochen aegypticus; H1N8, Baberspan wetlands; H4N2, Oudtshoorn region) were sequenced, genetically analyzed, and compared to previous South African isolates and viruses in the public data banks. An H5N8 strain was also detected by reverse-transcription PCR in cloacal swabs from swift terns (Sterna bergii) in the Mosselbaai region during 2007, although a virus could not be isolated. Initial phylogenetic results indicate that H6N8 and H9N2 ostrich and H10N7 Pekin duck viruses originated in the wild bird population that is geographically dispersed throughout southern Africa, based on the reassortment of viral genes from birds sampled outside of the ostrich farming areas. No evidence of internal genes associated with Asian HPAI H5N1 strains were detected in the South African isolates.

Influenza A Virus Coinfection through Transmission Can Support High Levels of Reassortment

“…Reassortment between human H1N1 and H3N2 lineages is detected more rarely but gave rise to an H1N2 virus that circulated widely in the United Kingdom in 2001-2002 (20, 21). Reassortment among avian influenza viruses in birds is highly prevalent and has a major impact on viral population structure in avian reservoirs (22)(23)(24)(25)(26)(27)(28)(29)(30). Thus, reassortment between IAV from two distinct sources occurs in nature and can have major consequences for the epidemiology of the virus in humans and other natural hosts.…”

Mouse-Adapted H9N2 Influenza A Virus PB2 Protein M147L and E627K Mutations Are Critical for High Virulence

“…H9N2 influenza viruses circulate worldwide and are endemic in multiple terrestrial avian species in Asia [1], [2], [3], [4]. It is noteworthy that H9N2 influenza viruses in poultry have occasionally been transmitted to mammalian species, including humans and pigs [5], [6], [7], [8], [9].…”

Influenza Virus A (H10N7) in Chickens and Poultry Abattoir Workers, Australia

“…Reported outbreaks of low pathogenicity avian influenza (LPAI) viruses of influenza A subtype H10 in poultry are uncommon but have occurred among turkeys and emus in the United States ( 1 , 2 ), farmed Pekin ducks in South Africa ( 3 ), and chickens in Canada ( 4 ). Isolation of influenza virus A (H10N7) was reported in Italy from smuggled poultry products from China ( 5 ).…”