Cassandra M Berry
Highly pathogenic avian influenza (HPAI) H5N1 virus strains have emerged as zoonotic viral pathogens over
the last decade and have eluded our serious attempts of control in domestic poultry by vaccination, with numerous countries continuing to have epidemic waves. Although the biology and genomics of H5N1 influenza viruses are well characterized, viral outbreaks still occur in domestic poultry, posing a dangerous threat of human transmission. There are two main types of current vaccines, inactivated whole virus vaccines and virus vaccines engineered by reverse genetics, both of which are administered with an adjuvant to hatchlings and optimally require a booster. However, immunological determinants of vaccine efficacy need to be considered distinctly in chickens and ducks. Our futile attempts to control H5N1 viral outbreaks in domestic poultry flocks question our capacity for future achievements of eradicating circulating H5N1 influenza viruses. There is a need for detection of infection and vaccination of domestic poultry to control potentially deadly but silent infection in vaccinated flocks. A positive marker strategy using tetanus
toxoid has several advantages over other negative markers to enable differentiation of infected from vaccinated animals (DIVA) for more effective control programs of HPAI in order to minimize the likelihood of an avian H5N1 influenza pandemic.