Experimental infection of ostriches with H7N1 low pathogenic and H5N8 clade 2.3.4.4B highly pathogenic influenza A viruses

• Published in: Veterinary microbiology 2021-12, Vol.263, p.109251-109251, Article 109251
• Main Authors: Abolnik, Celia, Ostmann, Erich, Woods, Matthew, Wandrag, Daniel B.R., Grewar, John, Roberts, Laura, Olivier, Adriaan J.
• Format: Article
• Language: English
• Subjects: Animals; Antisera; Conjunctivitis; Exo-a-sialidase; Experimental infection; Feathers; High pathogenic avian influenza; Host-pathogen interactions; Infections; Influenza; Influenza A; Influenza A Virus, H5N8 Subtype - pathogenicity; Influenza A Virus, H7N1 Subtype - pathogenicity; Influenza in Birds - virology; Low pathogenic avian influenza; Morbidity; Ostriches; Pulp; Rhinitis; Struthioniformes; Viruses
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/j.vetmic.2021.109251

•Ostriches infected with H7N1 LPAIV or H5N8 HPAIV shed similar amounts of virus from the tracheas.•Tracheal shedding duration was at least 14 days for H7N1 LPAIV and just beyond 14 days for H5N8 HPAIV.•Influenza A viruses in wing and/or tail feather pulp were evaluated for the first time in ratites.•Only ostrich tracheal swabs with RT-qPCR Ct values < 30 yielded virus isolates in eggs.•RDE treatment of sera prior to HI tests was required to avoid false positive results in H5-infected ostriches. Infection dynamics data for influenza A virus in a species is important for understanding host-pathogen interactions and developing effective control strategies. Seven-week-old ostriches challenged with H7N1 low pathogenic viruses (LPAIV) or clade 2.3.4.4B H5N8 high pathogenic viruses (HPAIV) were co- housed with non-challenged contacts. Clinical signs, virus shed in the trachea, cloaca, and feather pulp, and antibody responses were quantified over 14 days. H7N1 LPAIV-infected ostriches remained generally healthy with some showing signs of mild conjunctivitis and rhinitis attributed to Mycoplasma co-infection. Mean tracheal virus shedding titres in contact birds peaked 3 days (106.2 EID50 equivalents / ml) and 9 days (105.28 EID50 equivalents / ml) after introduction, lasting for at least 13 days post infection. Cloacal shedding was substantially lower and ceased within 10 days of onset, and low virus levels were detected in wing feather pulp up until day 14. H5N8 HPAIV -infected ostriches showed various degrees of morbidity, with 2/3 mortalities in the in-contact group. Mean tracheal shedding in contact birds peaked 8 days after introduction (106.32 EID50 equivalents/ ml) and lasted beyond 14 days in survivors. Cloacal shedding and virus in feather pulp was generally higher and more consistently positive compared to H7N1 LPAIV, and was also detectable at least until 14 days post infection in survivors. Antibodies against H5N8 HPAIV and H7N1 LPAIV only appeared after day 7 post exposure, with higher titres induced by the HPAIV compared to the LPAIV, and neuraminidase treatment was essential to remove non-specific inhibitors from the H5N8-positive antisera.