Submitted to: American Association of Avian Pathologists
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2016
Publication Date: N/A
Technical Abstract: Wild aquatic birds have been associated with the intercontinental spread of H5 subtype highly pathogenic avian influenza (HPAI) viruses, but wild waterfowl have not been implicated in the spread of other HPAI viruses. In a previous study we demonstrated that many H5 and H7 HPAI viruses could infect mallards when given at a high dose (10^6 50% egg infectious doses - EID50), and transmit to contacts. To continue addressing the role of waterfowl in the spread of HPAIV’s, the infectious dose and transmissibility of two HPAI viruses (Mexican H7N3 and US H7N8) was examined in mallards and compared to a mallard origin low pathogenic avian influenza (LPAI) virus. The mean bird infectious dose for the LPAI virus was <10^2 EID50 and the virus transmitted to all contacts. The US H7N8 HPAI virus also infected mallards with the low dose (10^2 EID50). For the Mexican H7N3 HPAI virus, the mean bird infectious dose was higher, the ducks requiring >10^4 EID50 to become infected. However, the titers of virus shed by the infected ducks were above this threshold (up to 10^6 EID50) and the viruses transmitted readily to contacts. None of the infected mallards showed clinical signs. This demonstrates that mallards can become infected with HPAI viruses if exposed, and highlights the importance of biosecurity measures during outbreaks of HPAI in poultry.