Avian influenza and health risk: conservation of endemic threatened wild birds in Sardinia Island

Sardinia is a Mediterranean island with a long geological history, leading to a separation process from continental Europe during Miocene. As a consequence, in this insular habitat some wild bird species developed endemic forms, some of which are currently threatened. The aim of this study is to evaluate the presence and the possible health risk associated with a potential avian influenza virus (AIV) circulation in Sardinian wild bird populations. Overall 147 cloacal swabs were sampled in the Sardinia Region from June 2009 to September 2011. Samples were obtained from 12 different taxonomic orders including 16 family and 40 species of birds. Based on the endangered host status or on the ecology of the host/virus interaction, samples were divided into three groups of species: endemic and/or endangered (n. 17 species), potential reservoir (n. 21 species) and potential spill-over (n. 2 species). Cloacal swabs were tested by reverse transcription (RT)-PCR for influenza A virus M-gene amplification. Forty-one serum samples were tested for antibodies against influenza A virus nucleoprotein by NP-ELISA and for detection of seropositivity against H5 and H7 AIV subtypes. No cloacal swabs tested RT-PCR positive for AIV, while two weak serological positive results were detected by NP-ELISA in a Mallard duck (Anas platyrhynchos) and in a Yellow-legged gull (Larus michahellis). The low or absent AIV circulation detected in Sardinia's wild birds during the study period, suggests a naїve status in these avian populations. A possible occurrence of AIV exposure of susceptible endemic species, might represent a cause of transition from compensatory to additive mortality which can contribute to increase a possible extinction process.