Figure 5.

Summary of experimental challenge study to assess the infectivity of influenza A viruses (IAVs) in mallards using inoculum comprised filtered surface water and paired cloacal and oropharyngeal swabs from ducks and maintained at ambient temperature in wetlands at Izembek National Wildlife Refuge, Alaska (AK) or Agassiz National Wildlife Refuge, Minnesota (MN) for a period of 209–229 days (d). Duck silhouettes indicate the number of mallards inoculated and have been colour-coded to denote the number of birds that were inferred to be negative for influenza A infection (white); positive for viral RNA via rRT-PCR only (yellow); positive for viral RNA and for which a bELISA provided evidence for seroconversion (orange); or positive for influenza A infection using all criteria (red) assessed in the challenge study (i.e. rRT-PCR, bELISA and isolation of IAV nearly identical to virus in inoculum as confirmed via genomic sequencing). The inverted duck silhouette indicates the euthanasia of a single mallard 24 h post-inoculation. Sample numbers, cycle threshold values (Ct) and field sites corresponding to inoculum are indicated to the right of virus icons. Maps of AK and MN courtesy of FreeVectorMaps.com (http://freevectormaps.com). The duck silhouette was downloaded from PhyloPic (http://phylopic.org/) and used under public domain (image by Sharon Wegner-Larsen). (Online version in colour.)