Landscape and spatial patterns of avian influenza virus in Danish wild
birds, 2006-2020
Abstract
Avian influenza (AI) is a contagious disease of birds with zoonotic
potential. AI virus (AIV) can infect most bird species, but clinical
signs and mortality vary. Assessing the distribution and factors
affecting AI incidence can direct targeted surveillance to areas at risk
of disease outbreaks, or help identify disease hotspots or areas with
inadequate surveillance. Using virus surveillance data from passive and
active AIV wild bird surveillance, 20062020, we investigated the
association between a range of landscape factors and game bird release
and the presence of AIV. Furthermore, we assessed potential bias in the
passive AIV surveillance data submitted by the public, via factors
related to public accessibility. Lastly, we tested the AIV data for
possible hot and cold spots within Denmark. The passive surveillance
data was biased regarding accessibility to areas (distance to roads,
cities and coast) compared to random locations within Denmark. We found
significant effects of variables related to coast, wetlands and cities
for the passive and active AIV surveillance data (P< 0.01),
but found no significant effect of game bird release. We used these
variables to predict the risk of AIV presence throughout Denmark, and
found high-risk areas concentrated along the coast and fjords. For both
passive and active surveillance data, low-risk clusters were mainly seen
in Jutland and northern Zealand, whereas high-risk clusters were found
in Jutland, Zealand, Funen and the southern Isles such as Lolland and
Falster. Our results suggest that landscape affects AIV presence, as
coastal areas and wetlands attract waterfowl and migrating birds and
therefore might increase the potential for AIV transmission. These
findings have enabled us to create risk maps of AIV incidence in wild
birds and pinpoint high-risk clusters within Denmark. This will aid
targeted surveillance efforts within Denmark and potentially aid in
planning the location of future poultry farms.