Unusual Suspects: Diving Ducks and Avian influenza
Due to the global threat to health and human safety posed by avian influenza monitoring has been conducted in the United States to determine the prevalence of such viruses in our wild waterfowl.
Due to the global threat to health and human safety posed by avian influenza monitoring has been conducted in the United States to determine the prevalence of such viruses in our wild waterfowl. However, such efforts have historically been focused predominately on dabbling ducks such as mallards, with little being known about the potential for diving ducks to contract and spread highly pathogenic avian influenza. The need to include diving ducks in research efforts became clear when researchers investigating the 2016 H7N8 outbreak in domestic turkey in Indiana reached a conclusion about how this novel strain emerged. The researchers reported that a related low-pathogenic virus had likely circulated asymptomatically, or without symptoms, among wild diving ducks, particularly scaup which is a mid-sized black and white duck, until it was transmitted to domestic turkeys and evolved into a highly pathogenic form of bird flu.
To improve our understanding of the role diving ducks may play in the spread and persistence of different strains of avian influenza, scientists with the USGS and U.S. Department of Agriculture collaborated to test the susceptibility of captive ruddy ducks and lesser scaup, two prominent diving duck species, to highly pathogenic avian influenza and identify the potential for these species to spread the virus in the wild. None of the captive birds inoculated with the highly pathogenic avian influenza virus showed clinical signs of infection, meaning that infected birds appeared healthy even if they eventually died from the infection. Interestingly, the diving ducks tested in this study only shed or release the virus in their feces for seven days post infection, and shed lower quantities of virus during this time than dabbling ducks inoculated with the same viral strains in a previous study.
Data from this study suggests that while diving ducks are viable vectors for highly pathogenic avian influenza, they shed less virus during a shorter window of time than dabbling ducks. However, the potential for diving duck species to contribute to the spread of highly pathogenic avian influenza means that disease prevalence monitoring remains a vital need. Even with the knowledge gained from this work, many questions remain. USGS scientists will continue their research on avian influenza to keep pace with the constantly changing threat presented by this virus.
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