Veterinary News: Advances in Avian influenza research

News 01 

First detection of H4N6 subtype of avian influenza virus in mallard ducks (Anas platyrhynchos) in Israel

Avishai Lublin，Nikki Thie，Irina Shkoda，Luba Simanov，Gila Kahila Bar-Gal，Yigal Farnoushi，Roni King，Wayne M Getz，Pauline L Kamath，Rauri C K Bowie，Ran Nathan

PMID：35687561；DOI：10.1111/tbed.14610

Avian influenza virus (AIV) poses a serious threat to animal and human health worldwide. As wild waterfowl transmit AIV worldwide, investigating the prevalence of AIV in wild populations is critical to understanding pathogen transmission and predicting disease outbreaks in domestic animals and humans. In this study, H4N6 subtype AIV was isolated for the first time from faecal samples of wild green ducks (Anas platyrhynchos) in Israel. phylogenetic results of the HA and NA genes suggest that this strain is closely related to European and Asian isolates. As Israel is located along the Middle Arctic-African migratory route, it is presumed that the strain was probably introduced by migratory birds. Phylogenetic analysis of the isolate’s internal genes (PB1, PB2, PA, NP, M and NS) revealed a high degree of phylogenetic relatedness to other AIV subtypes, suggesting that a previous recombination event had occurred in this isolate. This H4N6 subtype of AIV has a high recombination rate, can infect healthy pigs and bind human receptors, and may cause zoonotic disease in the future.

News 02

 Overview of avian influenza in the EU, March-June 2022

European Food Safety Authority，European Centre for Disease Prevention and Control，European Union Reference Laboratory for Avian Influenza

PMID：35949938；PMCID：PMC9356771；DOI：10.2903/j.efsa.2022.7415

In 2021-2022, highly pathogenic avian influenza (HPAI) was the most serious epidemic in Europe, with 2,398 avian outbreaks in 36 European countries resulting in 46 million birds being culled. between 16 March and 10 June 2022, a total of 28 EU/EEA countries and the UK 1 182 strains of highly pathogenic avian influenza virus (HPAIV) were isolated from poultry (750 cases), wildlife (410 cases) and captive birds (22 cases). During the period under review, 86% of poultry outbreaks were due to HPAIV transmission, with France accounting for 68% of the overall poultry outbreaks, Hungary for 24% and the other affected countries for less than 2% each. Germany had the highest number of outbreaks in wild birds (158 cases), followed by the Netherlands (98 cases) and the UK (48 cases).

The results of genetic analyses suggest that the HPAIV currently endemic in Europe mainly belong to spectrum 2.3.4 b. Since the last report, four H5N6, two H9N2 and two H3N8 human infections have been reported in China and one H5N1 human infection has been reported in the USA. The risk of infection was assessed as low for the general population and low to moderate for occupationally exposed populations in the EU/EEA.

 News 03

Mutations at residues 127, 183 and 212 on the HA gene affect

Antigenicity, replication and pathogenicity of H9N2 avian influenza virus

Menglu Fan，Bing Liang，Yongzhen Zhao，Yaping Zhang，Qingzheng Liu，Miao Tian，Yiqing Zheng，Huizhi Xia，Yasuo Suzuki，Hualan Chen，Jihui Ping

PMID：34724348；DOI：10.1111/tbed.14363

The H9N2 subtype of avian influenza virus (AIV) is one of the major subtypes affecting the health of the poultry industry. In this study, two strains of H9N2 subtype AIV with similar genetic background but different antigenicity, named A/chicken/Jiangsu/75/2018 (JS/75) and A/chicken/Jiangsu/76/2018 (JS/76), were isolated from a poultry farm. Sequence analysis showed that JS/75 and JS/76 differed in three amino acid residues (127, 183 and 212) of haemagglutinin (HA). To explore the differences in biological properties between JS/75 and JS/76, six recombinant viruses were generated using a reverse genetic approach with A/Puerto Rico/8/1934 (PR8) as the main chain. Data from chicken attack tests and HI tests showed that r-76/PR8 exhibited the most pronounced antigenic escape due to amino acid mutations at positions 127 and 183 in the HA gene. Further studies confirmed that glycosylation at the 127N site occurred in JS/76 and its mutants. Receptor binding assays showed that all recombinant viruses, except the 127N glycosylation-deficient mutant, readily bound to humanoid receptors. Growth kinetics and mouse attack assays showed that the 127N-glycosylated virus replicated less in A549 cells and was less pathogenic in mice compared to the wild-type virus. Thus, glycosylation and amino acid mutations in the HA gene are responsible for the differences in antigenicity and pathogenicity of the 2 H9N2 strains.

Source: China Animal Health and Epidemiology Center