The risks from H5N1 to wild birds from captive-reared mallard: Quick scoping review.
Abstract
This scoping review examined the potential risks of H5N1 dissemination into wild bird populations due to the release of captive-reared mallards. A comprehensive search of published literature on avian influenza in waterfowl, mallard rearing and release practices, and H5N1 epidemiology using databases such as CABDirect, Scopus, and Google Scholar was conducted. The review questions addressed each step in the epidemiological pathway linking captive-reared mallards and wild birds, assessing the likelihood at each step using predefined criteria. The online searches yielded 5530 records, which were screened to select 87 relevant papers read in full. Results showed a high likelihood that captive-reared mallards will be exposed to and infected with H5N1 following release, given the virus's persistence in the environment and the susceptibility of mallards. Infected mallards are likely to disseminate H5N1 due to their high viral shedding and frequent contact with wild waterfowl. Additionally, bridging species and mammals could be infected via contaminated environments or direct contact with infected mallards. The review concludes that the ongoing release of captive-reared mallards poses a very high risk to wild birds from H5N1 (high certainty).