Avian Influenza Surveillance in the Danube Delta Using Sentinel Geese and Ducks

Highly pathogenic avian influenza (HPAI) H5N1 virus incursions from migrating birds have occurred multiple times in Romania since 2005. Beginning in September 2008 through April 2013, seasonal sentinel surveillance for avian influenza A viruses (AIVs) using domestic geese (Anser cygnoides) and ducks (Anas platyrhynchos) in the Danube Delta was established by placing 15 geese and 5 ducks at seven sites. Tracheal and cloacal swabs, and sera collections (starting in 2009) were taken monthly. We studied a total of 580 domestic birds and collected 5,520 cloacal and tracheal swabs from each and 2,760 sera samples. All swabs were studied with real-time reverse transcription polymerase chain reaction (rRT-PCR) for evidence of AIV. Serological samples were studied with hemagglutination inhibition assays against avian H5, H7, and H9 influenza viruses. From 2009 to 2013, 47 swab specimens from Cot Candura, Enisala, and Saon screened positive for AIV; further subtyping demonstrated that 14 ducks and 20 geese had cloacal evidence of H5N3 carriage. Correspondingly, 4 to 12 weeks after these molecular detections, sentinel bird sera revealed elevated HI titers against H5 virus antigens. We posit that domestic bird surveillance is an effective method to conduct AIV surveillance among migrating birds in delta areas.