Birds of the order Psittaciformes are - besides chickens, turkeys and other birds - also susceptible to
infection with
avian influenza A viruses (AIV) and succumb following severe disease within one week. Published data prove that various parakeets, amazons, cockatoos, African grey parrots and budgerigars (genera Barnardius, Psittacula, Cacatua, Eolophus, Amazona, Myiopsitta, Psittacus and Melopsittacus) were found dead following natural
infections. Natural
infections of highly pathogenic
avian influenza viruses (HPAIV) of the haemagglutinin subtypes H5 and H7 cause severe disease and high rates of mortality. Experimental transmission studies with AlVs of the subtypes H5 and H7 confirm these data. Viruses of the subtypes H3N8, H4N6, H4N8, H11N6 and H11N8 may cause also clinical signs and occasionally losses in naturally infected psittacine birds. Clinical signs and losses were also noted following experimental
infection of budgerigars with a H4N6 virus. In the EU and in other countries, vaccination of exposed exotic and rare birds and poultry is a possible and an acceptable measure to provide protection. Currently, the EU Commission accepts inactivated adjuvanted
vaccines whereas in some other countries recently developed vector
vaccines are applied. However, birds remain susceptible during the time interval between application of any
vaccine and the development of immunity. This critical period can be bridged with
antiviral drugs. Our in ovo studies demonstrate that the
neuraminidase inhibitor
oseltamivir is non-toxic for chicken embryos at concentrations of 0.1, 1.0 and 10.0 mg/kg
body weight. These dosages prevented entirely the replication of a HPAIV of the subtype H7N1 when this
drug is given shortly prior to, simultaneously or soon after inoculation of chicken embryos with this AIV. Thus, we speculate that exposed valuable birds such as psittacines at risk can be successfully treated.