Surveillance for avian influenza viruses in wild birds in Denmark and Greenland, 2007-2010

Avian influenza (AI) is a disease of major threat to poultry production. Surveillance of AI in wild birds contributes to the control of AI. In Denmark (DK) and Greenland (GL), extensive surveillance of AI viruses in the wild bird population has been conducted. The surveillance aimed at detecting viruses of both high pathogenic AI (HPAI) subtypes H5 and H7, and low pathogenic AI (LPAI). Captured live wild birds and shot game birds were sampled by swabbing of the oropharyngeal and/or cloacal tracts, or swabs were collected from faecal droppings. In DK, most samples were collected in major staging areas for migratory waterfowl, whereas in GL, samples were collected in breeding areas. Samples from birds found dead at scattered locations across DK were sampled by oropharyngeal swabbing. 17530 wild birds from DK were tested as part of the surveillance during 2006-2010, of which 1614 were birds found dead. During 2007-2010, 2926 live wild birds from GL were tested. Swab samples were tested by RT-PCR and culturing. Positive samples were subtyped and the pathogenicity was determined by HA cleavage site sequencing. HPAI H5N1 was detected only during spring 2006, in 44 wild birds from DK. LPAI H5 and H7 subtypes were detected throughout the period together with several other LPAI subtypes. In GL, HPAI was not detected, but few samples were PCR positive for AI. The occurrence of AI subtypes in the wild bird population correlates with concurrent outbreaks of LPAI in Danish poultry, which may suggest virus transmission between these populations